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Part 1 – Stratospheric Ozone Depletion

Part 2 – Loss of Biosphere Integrity

Part 3 – Climate Change

Part 4 – Ocean Acidification

The biogeochemical flows, this planetary boundary is referring to, is the phosphorus cycle and the nitrogen cycle. These cycles happen naturally in nature over time, and without our intervention, remain in balance.

Let’s start with nitrogen

Nitrogen makes up 78% of the air we breath and so, it is all around us. This gas is made of two atoms with triple bonds. These bonds are very difficult to break. Plants and animals, including us, need nitrogen to survive. We cannot use the nitrogen in the air and neither can plants. So how do we access this nitrogen?
Tiny microscopic bacteria that live in the soil take nitrogen from the air and fix it into the soil. These bacteria produce enzymes that break these triple bonds and put nitrogen into a form that is accessible to plants. We can then access our nitrogen requirements by eating the plants. Nitrogen is returned back into the system when plants and animals die or when animals urinate or produce manure. Plants take this nitrogen up from the soil to grow. There are also special bacteria that convert this accessible nitrogen into atmospheric nitrogen or nitrogen gas. Another name for this  gas is dinitrogen.

Commercial agriculture uses synthetically made nitrogen to fertilize crops but this chemical leaches into rivers and lakes when it rains and causes algae blooms. When the algae dies, bacteria break them down but consume all the oxygen in the water by doing so. These oxygen consuming bacteria turn the river or lake into a dead zone. It’s called a dead zone because no other aquatic life can survive in water without oxygen. America’s dead zone off the eastern coast is visible from space. 

You can see from looking at the planetary boundaries picture, that we have crossed this boundary into the red high risk areas. This means we have too many dead zones around the world because of nitrogen pollution in seas and lakes. Commercial agriculture takes a lot unhealthy shortcuts to produce food but affects the natural balance of nature and thus negatively impacts our ecology. Permaculture methods do not use chemical fertilizers but lets nature do the work for us. 

The Phosphorus Cycle

Phosphorus is found in rock especially sediment layers and with constant weathering, is released into the ground. Plants take up phosphorus from the ground and we take up our needed phosphorus from plants. When animals and plants die, this phosphorus is returned back to the soil or runs into the sea, becomes a sedimentary layer and in a few million years, pops up as a mountain exposed to weather again. It’s a really slow process.

Commercial agriculture has messed up the phosphorus cycle so badly, that it is becoming deplete in the soil. Phosphorus is mined and used in chemical fertilisers that commercial farmers use. Permaculture does not use synthetic fertlizers to grow crops and harmonises with nature’s processes. Permaculture is the sustainable and regenerative method of farming because it treats the land as a permanent source of nutrition by building top soil and not depeleting it.

Nitrogen and phosphorus cycles
The Phosphorus Paradox
Fritz Haber – his paradoxical life
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Virgilia Divaricata – The Tree of Choice

Also known as Keurboom, Tree-In-A-Hurry and Blossom Tree.
This tree is leguminous meaning it is a nitrogen fixer.

Growing Virgilia

The attractive fragrant flowers and the fast growth rate make the keurboom a popular tree for the garden. Of the two, Virgilia divaricata is the better choice as its foliage is more luxuriant, and its growth more compact and it is amazingly beautiful when in full flower.

A keurboom is the perfect tree for the new, bare garden because it grows so fast it will take only two or three years before it will be creating shade, or a screen, and filtering the wind – which is an important consideration in Cape Town suburbs. It is also one of the best species to use as a pioneer in the first stage in the succession to forest. It is happy to grow out in the open, grows fast and quickly and creates the shade that the slower-growing, more permanent trees need to grow in.

Virgilia is propagated from seed. The seed coat is hard and requires some stimulation to initiate germination. Seeds can be soaked in hot water before sowing, or the seed coat can be cracked artificially. They also respond to stimulation by fire and can be treated with the Kirstenbosch Instant Smoke Plus Seed Primer. Seed should be sown in autumn or spring, in well-drained soil at a depth of 0.5 – 1 cm and covered with the sowing medium or milled bark and then watered. Seed can also be sown in situ, e.g. for forest rehabilitation projects. The seeds are highly fertile and can remain alive for many years after they have fallen, even after as many as 30 years they will germinate if conditions are favourable.

Transplant the seedlings after the first pair of true leaves has emerged when they are large enough to handle. Virgilia seedlings grow fast and can be planted into pots or bags for growing in, or directly into their permanent position in the garden. Feed moderately with a liquid fertilizer and water generously. Plant the young trees into a permanent location in full sun or semi-shade. They need good, light soil and plenty of water, particularly during their first 2 to 6 years. Virgilias have strongly spreading surface roots and are greedy feeders; they will benefit from frequent generous applications of compost or organic mulch. Virgilias are sensitive to frost, particularly when young. Mature trees may withstand short periods of frost, but not prolonged exposure to freezing temperatures.


  • Coates Palgrave, M. 2002. Keith Coates Palgrave Trees of southern Africa, edn 3. Struik, Cape Town.
  • Goldblatt, P. & Manning, J. 2000. Cape plants. A conspectus of the Cape flora of South Africa. National Botanical Institute, Pretoria & Missouri Botanical Garden.
  • Palmer, E. & Pitman, J. 1972. Trees of southern Africa. Balkema, Cape Town.
  • Phillips, E.P. 1928. Virgilia capensis. The Flowering Plants of South Africa 8: t. 305.
  • Smith, C.A. 1966. Common names of South African plants. Memoirs of the Botanical Survey of South Africa No. 35.
  • Van Wyk, B. & Van Wyk, P. 1997. Field guide to trees of southern Africa. Struik, Cape Town.

Giles Mbambezeli & Alice Notten
Kirstenbosch National Botanical Garden
August 2003

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The Power of Trees

Trees are incredible forms of life on this planet.

I can write pages and pages about them. If you knew what I knew about trees, perhaps you would hug them too now and again. They are essential to our existence and without trees, our planet would be inhabitable. I cannot empahsise enough how we must strive to plant them, whenever we can, and in many places as we can.


Just because you don’t have a garden, does not mean you cannot plant a tree.  Enhance public spaces like parks and sidewalks with trees. Choosing an indigenous and water wise species will increase chances of survival and not consume too much water.

Here are some important facts you should know about trees:

1. Trees seed rain

Trees transpire water which form clouds and rain back down. Check out these awesome videos which explain the process.


2. Trees increase the fertility of the soil

The leaves that fall off the trees, cover and protect the ground from evaporation. Microorganisms and other small creatures like worms, eat the organic matter and process it into nutritious soil for plants. The oranic matter becomes food for the ground. There are also trees that absorb nitrogen from their air and return it to the soil through their leaf litter and nodes in their roots. If the tree is large enough to prune, the stored nitrogen in the root nodes are released into the soil as the tree balances its roots with its canapy. When deciduous trees lose their leaves in autumn, you can decide how you would like to use them, as they have great fertilizing qualities.


You can choose to rake up the leaves, and store them to make leaf mould. Leaf mould is an excellent form of compost, or you can let nature do all the work for you by leaving them on the ground. Fallen leaves have a wonderful purpose, they protect the ground  from extreme cold or heat. Leaves (as mulch) stop water evaporation and when the worms eat them, they turn them into super compost for the soil. This is nature’s cycle of returning nutrients back to the soil so that more life can grow.

3. Trees stabilize the soil

The roots dig deep into the soil to secure the tree and this also protects the soil from soil erosion. Soil erosion occurs when rains fall and top soil is washed away where there are no trees to hold the soil in place. This leaves big gaping holes where it is difficult to grow anything.


4. Trees provide shade and regulate temperature.

If you measured the temperature of various man made things like tar roads, concrete, bricks and steel and then compared those temperatures with the tops of trees, you will see a big difference. Trees regulate the temperature. Man made structures like roads and concrete increase the temperature in cities and contribute to global warming. I am sure all of you have experienced the sanctuary of shade underneath a tree on a very hot day.


5. Trees help in the maintenance of biodiversity and ecosystem balance.

Trees provide a home to wildlife and increase chances of survival of many species. They provide food and shelter. Where many species live together, a balance is retored and is called an ecosystem. An ecosystem can fall out of balance if a species of life is removed and this threatens the survival of all other life. Biodiversity is key for survival of all species.


6. Trees are a resource for fuel and building

Wood from the fallen and dried branches of trees, can be burnt to provide warmth. Burning dried branches also makes coal which can be burnt or used to clean water. It can even clean our teeth! We can make things with wood like furniture, shelter and paper. We must be careful to prune for the trees health, and not cut them down. Destroying a forest for our own needs is selfish when there are better and more sustainable ways of providing for our comforts.

7. Trees store carbon

Do you know about all that carbon in the air that is making our planet hotter and making the sea acidic? Well, it should be in the ground or in trees where it is safe and put to good use. Trees store carbon and return it to the soil by decomposition.


The Moral of the Story

Go out there and plant a tree for Arbor month. Plant 10 trees if you can and try stick to indigenous, water wise trees. Let’s fix the grass deserts in our parks and restore the land, climate and wildlife with trees. Plant some fruit or nut trees in your garden and you will be rewarded with delicious food.

Trees are so vital to our survival. We need more of them to fix the damage we have done to this planet.  Plant a tree for Arbor Month.



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July is not really a planting month for vegetables, but you can still plant :

– Beetroot seeds
– Cape Gooseberry seeds in seed trays
– Cauliflower seeds
-Celery seeds
– Mint seeds
– Mustard greens/Cress seeds
– Pea seeds
– Potatoes
– Radish seeds
– Shallot seedlings
– Swedes/Rutabagas seeds
– Tomato seedlings
– Turnip seeds


Now is a good time to start planning your summer garden early in the month so you have enough time to source and purchase open pollinated seeds for early sowing.

Carry out soil tests, particularly on land where growth for one or more seasons has been poor. Here is a link to understand soil tests.

After winter crops have been removed, dig the ground well over and incorporate dressings of organic matter.

Broad beans can be side dressed, earthed up and given support with string or wire if required

Apple trees and grapevines can be pruned to ensure healthy growth.

In mild conditions, tomatoes can be sowed in seed boxes.

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Once upon a time,

there was an unhappy women driving home from work. Her name was Hilda. It was late and dark in the evening. Her feet were freezing and the heater in her rusty car didn’t work. She worked long hours and her boss was a mean, demanding man who always told her that he wanted ‘his pound of flesh’ when he wanted her to work late with no overtime pay.

She felt hopeless because she didn’t know how to change her circumstances. She was mentally and physically exhausted and there was not much room in her heart left for extra care.

She didn’t earn very much and could’t afford to fill a basket let alone a trolley when she did her weekly grocery shopping.

One day, she was weeping on the couch and drinking cheap red box wine. Her elderly tortoise-shell cat ,she rescued 8 years ago, sat on her lap and tried to comfort her in his own way by purring and pressing his paws against her in a kneading fashion. He was soft and calm in times like these. Hilda felt grateful for his company and concern.

She heard a knock at the door.

She was too tired for anything and ignored the knocking. The visitor knocked again. This time, the knocking was louder and sounded more determined. She got up and opened the door, and there was a familiar face. It was the neighbour she bumped into occasionally in the road, and also at the local grocery store. Her name from Saffron.

Saffron was holding a big box under her arm and asked if she could come in. Hilda, embarrassed that she was in her pajamas with slippers that were falling apart and a messy house, opened the door for Hilda to come in.

Saffron noticed that Hilda had been crying and drinking alone but decided not to ask about it. Instead, she proudly announced to Hilda that she had opened a seed library. Hilda looked confused.


Saffron enthusiastically explained that a seed library works just like a book library.

You can choose what seeds to borrow, just like you would choose a book that sparks your interest at the library. You borrow the seeds and the library makes a record of what seeds they are. Once the seeds are withdrawn, the lender goes home or to a community garden, to grow the seeds. Once the vegetables or flowers have grown, some are harvested for personal use and some vegetables are left to grow longer. These vegetables that grow longer eventually make flowers and then seeds. The seeds are then collected and dried. The dried seeds are split into two. A small portion goes back to the seed library and the rest can be kept to grow food during the next growing season.

This was all very new to Hilda and without realising it, she started shaking her head. She didn’t have a big garden which was full of overgrown weeds and uncut grass anyway. She explained to Saffron that she didn’t know about gardening and that she didn’t have any space.


Saffron placed the box on the coffee table and opened it.

Inside were lots of small brown envelopes with hand written labels and inside those envelopes were various seeds. Saffron put on her pink glasses that were hanging around her neck and flipped through the little brown envelopes. She picked three out after squinting her eyes at some of the labels.

“I tell you what, Hilda!” she said. “Here are some spinach seeds, they grow in almost anything. I see you have a few pots lying around your stoep with dead plants in them. Try growing some tomatoes and peppers in them. They do well in pots.”
Hilda responded with “Um…” but Saffron interrupted her and said, “Just try it Hilda, it will be good for you. Imagine! If you can grow these easy vegetables, you will never have to buy them again. Gardening is good for the soul!” She wanted to say that it looked like Hilda could do with some therapy and get off the couch but she decided not to. That would be unkind and would do no help in this situation.


Hilda shrugged and accepted the seeds.

Saffron made a few notes in her scrappy book filled with dog ears and coffee stains and suddenly declared that she was late and had to hurry home.
She shut her box abruptly with a loud slam and put it back under her arm. Saffron gave Hilda a firm one armed hug. Hilda almost fell over but managed to regain her balance.
Saffron was out of the door in less than two seconds and Hilda went to the threshold to call “Bye” to Saffron. “Thank you”, she yelled just before Saffron slammed her car door, started the ignition and sped off.

Hilda imagined Saffron on a broom stick with a pointy black hat and then chuckled to herself. Maybe she had too much wine. She caught her reflection in the picture frame on the wall and noticed her teeth were red. How embarrassing, she thought and then went to pour another glass of wine.

A month went by and Hilda left the seeds on the coffee table.

She saw them everyday. About 2 months later, while Hilda was cleaning the house on a sunny Saturday morning, she looked at the seeds which were still lying on the coffee table. She felt a little irritated that they were still there and decided to plant the seeds.

Two weeks later, after locking the front door and rushing to the car, she noticed small seedlings in the ground. She took a few steps back to examine them.
A flicker of excitement lit up in her heart and she felt maternal over the tiny two leaved plants that had poked up through the ground. Some still had seed shells attached to them. It was like a new birth.

She stared at the seedlings in wonder for about a minute and then realised once again that she was late for work. She thought about her new plants during the day and couldn’t wait to get home to see if they grew some more while she was working at the office.

Hilda looked after her new plants and sent Saffron pictures to show her progress.

Saffron replied with messages of encouragement which were cluttered with emoticons.
With Saffron’s guidance, Hilda left some plants to seed and harvested them. She returned a portion back to Saffron’s seed library and kept the rest for herself.

Hilda found therapy in her gardening. The care and love she put into it was meditative and it gave her a sense of peace. She realised how much more delicious her vegetables were than those that were sold at the grocery store.

Two years later, Hilda had a thriving vegetable patch. She started vertical gardening and sold strawberries at the local farmers market. Her strawberries were so popular that she started hosting workshops on growing strawberries in urban spaces. She no longer had to work in a boring and uncomfortable office for a stressful boss.

Hilda was happier

and felt like she was doing her part for the environment by recycling her kitchen scraps into compost and growing her own food.

If you would like to borrow some seeds, contact us. We would love to share them with you. We also welcome heirloom seed contributions too.
For more information about why we wrote this story, click here to read our previous blog about seed biodiversity and here about home food gardening. I recommend watching the movie SEED The Untold Story by Collective Eye Films.

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Worm Castings
Vermicast is probably the best fertiliser you can add to your garden to get the best results. It doesn’t matter what kind of soil you have, by adding vermicast, you can’t go wrong. It is the elite of the elite when it comes to soil conditioning and we will tell you all about it with references to scientific research if that tickles your fancy. Unicorn Cafe is all about the science of how things work and if we cannot explain why then we don’t promote 😉

There is also a case study at the end of this article proving how one farmer benefitted from using vermicast.

Consider the following; Vermicast has been around since the start of time, it is not manmade and it occurs naturally in healthy soil ecosystems. If you dig into the forest floor in the Knysna indigenous forests, you will find earthworms processing the fallen organic material. Consider the health and size of the centuries old trees around you that thrive there without any fertiliser or irrigation from man.

Vermicast is a thick black natural compound produced by earthworms. It is a fundamental part of natures soil building process. Vermicast harbours all the components  necessary to build and develop soil into a physically, chemically and biologically healthy growing medium for plants to thrive.

Vermicast repairs soil structure to significantly reduce irrigation requirements & associated costs. This means that when using vermicast, you will need less water. It stabilises moisture levels within soil so that the water doesn’t completely run through in sandy soils or become waterlogged and rot roots or seeds in clay soils. With stabile moisture levels in the soil, moisture is always available consistantly to the roots which reduces plant stress.

Vermicast reseeds plant beneficial bacteria, which is the crucial gateway between soil and plant roots. This means that vermicast helps roots absorb what they need from the soil.  Worm castings release minerals held within mineral sand for plant availability and repair the  structure of soil, reducing soil erosion risks. When you have worm castings in your soil, the microbes in the castings ensure efficicient uptake of fertiliser additions.

Increased plant beneficial bacteria cultures increase the effective uptake and stabilisation within the soil of  added organic fertiliser. Peaks and troughs in availability leads to plant stress. This means that when plants are exposed to dips and highs of nutrient and moisture availability, they can become more stressed as opposed to a more constant and flatlined availability.
Reduced plant stress means stronger, healthier, more pest resistant plants, producing greater yields.

Vermicast boosts the pest resistant enzyme production in plants repelling insect attack and fungal infection.  Plant growth stimulants and hormones in vermicast encourage both the top growth above the soil, containing the leaf, stem and flower, and the root growth beneath the ground.

Vermicast is particularly effective during seed germination and reduces transplant shock. Vermicast’s beneficial microbes triggers the development of a healthy natural soil-food-web. It seeds and attracts earthworms and other good life into the soil; in turn aerating and conveying microbes and other plant beneficial hormones and plant growth stimulants.

Vermicast also increases the cationic exchange rate. This is the rate at which the cationic soil trace elements can attach themselves to vermicast. Everything in nature has an electrical charge. Some charges are positive (cations) and some are negative (anions). Organic vegetative matter is anionic and, as vermicast is highly concentrated  vegetative matter, it is strongly anionic. Most trace elements are cationic, and thus attracted to vermicast. In simple terms this means that trace elements are attracted to vermicast and readily bond to it in the same way that opposite poles of a magnet attract each other. Plants have a stronger pull than the vermicast and therefore draw the trace elements away from the vermicast and into their roots in a natural exchange system.

You can buy worm castings from us or you can make your own worm farm and harvest your very own worm castings. We published a DIY worm farm last year in October and you can find the article here to make your very own worm farm that you can keep in kitchen.

Various scientific trials & studies by a number of Universities (Cornell, Griffith &
Stellenbosch) on a variety of crops have resulted in the same base conclusion; vermicast (worm castings) are highly beneficial to plant growth, health and yield. Vermicast is a totally natural and organic product created by earthworms.

Joshi and Kelkar (1952) reported that earthworm casts contained greater percentage of finer fractions like silt and clay than in the surrounding soils. This change in mechanical composition of soil was probably due to the grinding action of earthworm gizzard. The chemical analysis of Vermicasts revealed that they were richer in soluble salts, neutral or alkaline in reaction and had higher percentage of exchangeable Na, K and Mg but a lower exchangeable Ca than in corresponding soil.

Earthworm casts also contained greater amounts of Nitrogen (N), Phosphorous (P) and Potassium (K). The Vermicasts contained higher amounts of nitrate nitrogen and possessed a greater nitrifying power than the corresponding soils. Vermicast also contained Mg, Ca, Fe, B, Mo and Zn in addition to some of the plant growth promoters and beneficial microflora. Several valuable compounds were also produced through the earthworm – microfloral interaction, which included vitamins such as B12 and plant growth hormones such as gibberellins.

This important concept, that Vermicompost includes plant-growth regulators which increase growth and yield, has been cited and is being further investigated by several researchers (Canellas et al, 2002). Earthworms increase the amount of mineralised nitrogen from organic matter in soil.
The microbial composition changes qualitatively and quantitatively during passage through the earthworm intestine (Pedersen & Hendriksen, 1993)
Vermicast is coated with mucopolysaccharides and enriched with nutrients. The cellulolytic, nitrifying and nitrogen fixing microbes are found established in the worm cast (Kale et al., 1988). Earthworms directly cycle the nitrogen by excretion in the casts, urine and mucoprotein and through the turnover of earthworm tissues (Lee, 1985) Barois et al., (1987) observed an activation of N mineralization, with the casts having 270 percent more ammonia than the bulk soil. Within a year of application of vermiculture technology to the saline soil, 37 percent more N, 67 percent more P2O5 and 10 percent more K2O were recorded as compared to chemical fertilizer (Phule, 1993).
Plant Growth Stimulants
Atiyeh at al (2002) conducted an extensive review. The authors stated that: “These investigations have demonstrated consistently that vermicomposted organic wastes have beneficial effects on plant growth independent of nutritional transformations and availability. Whether they are used as soil additives or as components of horticultural soil less media, vermicomposts have consistently improved seed germination, enhanced seedling growth and development, and increased plant productivity much more than would be possible from the mere conversion of mineral nutrients into more  plantavailable forms.”

Atiyeh et al. (2000) found that compost was higher in ammonium, while  Vermicompost tended to be higher in nitrates, which is the more plant- available form of nitrogen. Vermicast’s are excellent media for harbouring N-fixing bacteria (Bhole, 1992).
Earthworms have multiple, interactive effects on rates and patterns of  nitrogen mineralization and immobilisation in natural and managed ecosystems (Edwards and Lofty, 1977; Lee, 1983; Lavelle and Martin, 1992; Blair et al., 1995).

Earthworms not only disperse microorganisms important in food production but also associated with mycorrhizae and other root symbionts, biocontrol  agents and microbial antagonists of plant pathogens as well as microorganisms that act as pests (Edwards and Bohlen, 1996).
Several researchers have demonstrated the ability of earthworms to promote the dispersal of beneficial soil microorganisms through castings, including pseudomonads, rhizobia and mycorrhizal fungi (Edwards and Bohlen, 1996; Buckalew et al., 1982; Doube et al., 1994a; Doube et al., 1994b; Madsen and Alexander, 1982; Reddell and Spain, 1991; Rouelle, 1983; Stephens et al., 1994).
Earthworm casts are enriched in terms of available nutrients and microbial numbers and biomass, relative to the surrounding soil (Shaw and Pawluk, 1986; Lavelle and Martin, 1992)
Soil Benevolent Biota
Earthworms reject significant amounts of nutrients in their casts. In part these losses result from the intense microbial activity in their gut, and from their own metabolic activity. E.g. The elimination of N due to fast turnover of this element in microbial biomass. A significant proportion of C assimilated by earthworms is secreted as intestinal and cutaneous mucus with greater C:N ratios than those of the resource used (Lavelle et al., 1983; Cortez and Bouche, 1987).
Kale (1991) has attributed the improved growth in pastures and in other crops like rye and barley to the chemical exudates of the worms and the microbes associated with them.
Tomati et al., (1983) related the beneficial influence of worm cast to the biological factors like gibberellins, cytokinins and auxins released due to metabolic activity of the microbes harboured in the cast.
It has also been indicated that the chemical exudates of worms and those of microbes in the cast, influence the rooting or shoots of layers. In a field trial Kale and Bano (1986) observed that the seedling growth of rice in nursery increased significantly due to Vermicompost application, and transplanting of seedlings could be made one or two days earlier than the usual practice. After transplanting the growth of seedlings in the main field was more favourably influenced by worm castings than chemical fertilisers This was attributed to higher availability of nitrogen for plant growth. The improved growth was also attributed to the release of plant growth promoting compounds from vermicast, which in their opinion could easily replace the chemical fertilizers at nursery level.
Similarly, work at NSAC by Hammermeister et al. (2004) indicated that “Vermicomposted manure has higher N availability than conventionally composted manure on a weight basis”. The latter study also showed that the supply rate of several nutrients, including P, K, S and Mg, were increased by vermicomposting as compared with conventional composting.  These results are typical of what other researchers have found (Short et al., 1999; Saradha, 1997, Sudha and Kapoor, 2000).
It appears that the process of vermicomposting tends to result in higher levels of plant-availability of most nutrients than does the conventional composting process. The literature has less information on this subject than on nutrient availability, yet it is widely believed that vermicast greatly exceeds conventional compost with respect to the levels of beneficial microbial activity. Much of the work on this subject has been done at Ohio State University, led by Dr. Clive Edwards (Subler et al., 1998).
In an interview (Edwards, 1999), he stated that Vermicompost may be as much as 1000 times as microbially active as conventional compost, although that figure is not always achieved. Regulators which are relatively transient may become adsorbed on to humates and act in conjunction with them to influence plant growth”.  Moreover, he went on to say that “…these are microbes which are much better at transforming nutrients into forms readily taken up by plants than you find in compost – because we’re talking about thermophillic microbes in compost – so that the microbial spectrum is quite different and also much more beneficial in a vermicompost. I mean, I will stick by what I have said a number of times that a vermicompost is much, much preferable to a compost if you’re going in for a plant-growth medium.”
Many researchers have found that vermicast stimulates further plant growth even when the plants are already receiving optimal nutrition.
Atiyeh et al further speculate that the growth responses observed may be due to hormone-like activity associated with the high levels of humic acids and humates in vermicast: “…there seems a strong possibility that …plant-growth regulators which are relatively transient may become adsorbed on to humates and act in conjunction with them to influence plant growth”.
There has been considerable anecdotal evidence in recent years regarding the ability of vermicast to protect plants against various diseases. The theory is that the high levels of beneficial microorganisms in vermicast protect plants by out-competing pathogens for available resources (starving them, so to speak), while also blocking their access to plant roots by occupying all the available sites. This analysis is based on the concept of the “soil foodweb”, a soil-ecology-based approach pioneered by Dr. Elaine Ingham of Corvallis, Oregon (see her website at for more details).
Work on this attribute of vermicast is still in its infancy, but research by both Dr. Ingham’s labs and the Ohio State Soil Ecology Laboratory are very promising. Soil Benevolent Biota At the Ohio State Soil Ecology Lab, Edwards and Arancon (2004) report that “…we have researched the effects of relatively small applications of commercially-produced vermicomposts, on attacks by Pythium on cucumbers, Rhizoctonia on radishes in the greenhouse, and by Verticillium on strawberries and Phomopsis and Sphaerotheca fulginae on grapes in the field.
In all of these experiments, the Vermicompost applications suppressed the incidence of the disease significantly.” The authors go on to say that the pathogen suppression disappeared when the vermicast was sterilized, indicating that the mechanism involved was microbial antagonism. In addition, Edwards and Arancon (2004) report statistically significant decreases in arthropod (aphid, mealy bug, spider mite) populations, and subsequent reductions in plant damage, in tomato, pepper, and cabbage trials with 20% and 40% Vermicompost additions to Metro Mix 360 (the control).
They also found statistically  significant suppression of plant-parasitic nematodes in field trials with peppers, tomatoes, strawberries, and grapes. Moreover, the authors go on to state a finding that others have also reported (e.g., Arancon, 2004), that maximum benefit from vermicast is obtained when it constitutes between 10% and 40% of the growing medium. Further research is required, however, before vermicast can be considered as an alternative to pesticides or an alternative, non-toxic method of pest control, but these initial studies are highly encouraging.

Case Study

Apple Farming at Clan Leslie, Harrismith, Free State
Farmers Weekly 21 October 2010 – Hayden Green
By incorporating vermicomposting and worm-casting tea in its apple production system, Clan Leslie Estate has improved its fruit quality, reduced input costs and improved the soil and tree health in its orchards. Hayden Green visited Mike Leslie to find out more. Mike Leslie farms in partnership with his father Nick and brother Graham on the Clan Leslie Estate near Harrismith in the Free State. Mike’s farming philosophy is to keep things simple, but pay attention to detail. He’s passionate about apple production  and about where sustainability is taking the enterprise. He combines technology with applicable management and biological farming techniques to produce fruit that looks good, is healthy and nutritious, and exceeds export quality requirements. To achieve quality and production goals, Mike also partners with nature’s prime recycler – the humble earthworm.
Vermiculture – earthworm farming To branch out into exports, Clan Leslie established its apple production division in 1996. Five years ago, they decided to integrate vermiculture into the operation because of changing export regulations, specifically for chemical residue levels. “Our list of suitable chemicals was and still is shrinking due to global regulations and the green
movement,” Mike says. “Consumers are looking for residue-free fruit, and we had to find a different way of doing things.” Fruit destined for export is batch-tested five days before picking, and Mike felt that moving to natural pest and disease control in the form of “worm tea” would minimise the risk of residue on the fruit, increase its nutritional value, and reduce chemical use and withholding periods. He contacted private consultant Hennie Eksteen for advice on vermiculture, and partnered with vermiculture specialist Poerie Coetzee to manage it. This left Mike himself free to concentrate on orchard management.

“I was initially concerned that salmonella and E. coli contamination from feedlot manure and chicken litter we used as compost base came through in  the testing,” he admits. “But we tried the worm tea in selected apple blocks and the results were perfect. The earthworms destroyed all pathogens in the manure, giving us the confidence to freely use compost tea.”
Foliar and soil-feed teas “Foliar-feed tea requires an anaerobic process,” explains Mike. “We mix the earthworm castings with water, molasses, ground Lucerne and fishmeal, and brew the mixture in 1 000â vats for three weeks. When it’s ready, we dilute the tea with water and use it as a foliar feed, sprayed at 80â/ha.” Likewise, converting the solid material in worm castings into a liquid enables a practical, accurate and uniform application of soil-feed
tea throughout the orchard. Soil-feed tea is made aerobically by pumping a large volume of air through it for up to 24 hours. Once the correct microbe population is reached (established by microscopic examination), the tea must be applied undiluted at 200â/ha within a few hours before the aerobic bacteria die from a lack of oxygen. Follow-up irrigation further washes the tea into the soil. The total cost of foliar and soil-feed tea production and application is around R12 625/ha per season. This will decline in time as the orchard health improves and less spraying is needed. Mulching – retaining a natural balance
“In nature, fruiting trees are part of a complicated ecological system, existing in symbiotic relationships with the fauna and other flora to sustain a healthy fruiting cycle,” says Mike. He’s concerned about the consequences and economic sustainability of a system of constant harvesting, with synthetic chemicals as the only inputs. So, mimicking nature, he scatters tree pruning clippings and other plant residue around the base of the trees to eventually decompose and form mulch. “We use nine 1,5mdiameter round bales of wheat residue to every 200m of tree row,” he explains. “This equates to 104 bales, or 26t of dry plant material, per hectare, and lasts for three to four years. Nothing is wasted.” The mulch, besides retaining moisture, feeds the bacterial processes stimulated by the soil-feed worm tea. Mike points to the contrast between mineral soil and the rich organic matter resulting from earthworm activity. “The earthworms manage the environment for me,” he says. “The soil is moving towards a natural state of balance (homeostasis) without chemical fertiliser.” He estimates that this production system needs one-third less irrigation water. “The savings are significant.” Mike was astonished when he first saw the increase in root growth as a result of the mulch and soil feed. “This increased nutrient uptake has resulted in healthier, stronger apple trees.” A competitive advantage “Quality counts. The market is prepared to pay for an apple that tastes better and, more importantly, lasts longer,” says Mike. Mulching with worm tea had precisely this effect, increasing demand for Clan Leslie apples from clients in Africa, where the cold supply chain isn’t as advanced as other export markets. “The local informal market is massive, and is prepared to pay premium prices for quality fruit that will last,” he explains. Although being situated in the south-eastern Free State gives Clan Leslie a three-week harvesting advantage over its Cape competitors, the unseasonal heavy frosts are a problem. Mike warns that worm tea is no silver bullet, and that balancing the soil is a slow process. Over the last five years, he has recorded an average increase from 8 Brix to 12 Brix in his plants, correlating directly to frost resilience. An SMS early warning system notifies him to irrigate when air temperature drops below 5°C.
Incorporating earthworms has increased yields from 50t/ha to 75t/ha in Pink Lady apples, and by 15t/ha in other varieties. The path towards more sustainable production on the 66ha apple orchard constantly challenges Mike. “In the future I would define myself increasingly as a carbon farmer who produces apples,” he says. Based on the success of the worm tea in the  orchards, he aims to produce low-carbon-footprint apples with a superior nutritional value. Worm tea has been so successful in the apple orchards that he intends to expand it to the other Clan Leslie enterprises.
Contact Mike Leslie on 082 770 0306 or e-mail

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Gardening Tips for April

April is the time to plant :

– Angelica seeds
– Basil seeds 
– Broad Beans 
– Beetroot seeds
– Cabbage seeds
– Carrot seeds
– Cauliflower seeds
– Celeriac seeds
– Celery seeds 
– Chili/Hot Peppers seeds
– Chinese Cabbage seeds
– Chives seeds
– Collards seeds 
– Dill seeds
 – Endive seeds
– French Tarragon seeds
– Garlic
– Horseradish seeds
-Kale seeds
– Kohlrabi seeds
– Leek seeds
– Lettuce seeds
– Mint seeds
– Mizuna seeds
– Mustard Greens seeds
– Onion seeds
– Pak Choy seeds
– Parsley seeds
– Parsnip seeds
– Potatoes
– Radish seeds
– Rocket seeds
– Shallot seedlings
– Spinach seeds
– Spring Onion seeds
– Sunflower seedlings
– Swedes/Rutabagas seeds
– Sweet Marjoram seeds
– Swiss Chard seeds
– Thyme seeds
– Turnip seeds

You may still have seeds to harvest. Gather, clean and save them for their next growing season. Label them carefully and store away from light and moisture. It is a good idea to store the seeds in paper first so that they are protected from any condensation that may form.
Leaves make great mulch when stored for a year to make leaf mould so now is the perfect time to collect all leaves and store for a year.  You can also simply leave them on the floor to protect the soil and decompose naturally.

If you haven’t prepared beds yet, it is a good time to mix in compost for winter vegetable planting. Mound up celeries and leeks. Harvest pumpkins and dry before storing.   

Slugs, snails, aphids and white flies will be busy so be on the lookout and protect the plants that need protecting.

Fertilise fruit trees with compost tea or worm tea or a natural and organic fertilsier.  Now is the time to mulch. Top up mulch everywhere so that the soil is protected from the winter cold, retains moisture and suppresses weeds.

Autumn is also the season for bulbs so ensure your beds are well fed with plenty of nutrients.  If you are a sweet pea fan like I am, now is the time to set up stakes and plant those magical seeds that bring colour and aroma to the garden. Daisies, poppies and Namaqualand daisies can be planted.

As the temperatures drop, there will be more moisture in the soil so watering less creates more time for other tasks. Take note of the weather and adapt to the changing climate.

Plant a tree. With the current drought upon us, one of the best ways to do our part is to plant an indigenous tree so that when it rains, there is vegetation to act as a sponge and store the water, shade the soil and provide future mulch and nutrients. Plant a fruit tree or any tree that will bring you joy and is suitable for your garden, lifestyle so long as it does not cause harm to your neighbours or environment. A little bit of research goes a long way. Autumn is not a good time to prune in general as your plants will be shifting their focus to root growth rather than top growth and thus will not heal easily from pruning. 

The A – Z of Vegetable Gardening in South Africa by Jack Hadfield

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Gardening Tips for March

Clean up by pulling out dead plants and plants that have given their best like tomatoes, rocket and corn. Clean water features such as ponds and natural pools. Thin out plants if they are taking over and add all organic matter to the compost bin.

Harvest and save ripe seeds. Store in old envelopes or brown paper bags and label them with the name, colour and date.

Harvest herbs and dry out by hanging in cool shady place upside down.

Keep a look out for cutworms hiding underneath leaves. They are sometimes found more easily with a torch at night.


Start preparing beds for winter planting by feeding the soil with compost. It’s the time for root crops like beetroot, carrots, onions, radishes and parsnips. It’s also time to plant  leafy salad vegetables like lettuce and baby spinach. Other varieties to plant are peas, beans, kohlrabi, and spring onions, celery, spinach, pak choi, mizuna and mibuna.

Start preparing beds for winter planting by feeding the soil with compost. It’s the time for root crops like beetroot, carrots, onions, radishes and parsnips. It’s also time to plant  leafy salad vegetables like lettuce and baby spinach. Other varieties to plant are peas, beans, kohlrabi, and spring onions, celery, spinach, pak choi, mizuna and mibuna.

Add compost to all plants before the weather cools  to set plants in good stead for winter. Citrus trees will need regular feeding with compost and epsom salts if the leaves are yellowing. Top up on mulch to regulate temperatures especially while it’s still warm.

If you want to get your soil tested for deficiencies or monitor progress of improvement, now is a good time.

Thin out bulbous plants and replant.

Check roses and citrus trees for suckers growing below the main branches. Pull off by tugging downwards. This allows the main branches to grow without the competition of the suckers.

Take notes of how the summer season performed. What worked, what didn’t work.

Comprehensive food planting list for March :

  • Angelica seeds
  • Basil seeds 
  • Beetroott seeds
  • Broccoli seedlings
  • Brussels Sprouts seedlings
  • Cabbage seeds
  • Carrot seeds
  • Cauliflower seeds
  • Celeriac seeds
  • Celery seeds 
  • Chili/Hot Peppers seeds
  • Chinese Cabbage seeds
  • Chives seeds
  • Collards seeds 
  • Dill seeds
  • Endive seeds
  • French Tarragon seeds
  • Garlic
  • Horseradish seeds
  • Kale seeds
  • Kohlrabi seeds
  • Leek seeds
  • Lettuce seeds
  • Mint seeds
  • Mizuna seeds
  • Mustard Greens seeds
  • Onion seeds
  • Pak Choy seeds
  • Parsley seeds
  • Parsnip seeds
  • Potatoes
  • Radish seeds
  • Rocket seeds
  • Spinach seeds
  • Spring Onion seeds
  • Sunflower seedlings
  • Swedes/Rutabagas seeds
  • Sweet Marjoram seeds
  • Thyme seeds
  • Turnip seeds

The A – Z of Vegetable Gardening in South Africa by Jack Hadfield

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