Growing techniques


Robin Gale-Baker, from Sustainable Macleod, discusses various growing techniques. This is one of a series of articles she has written about growing techniques (see right hand sidebar). She has also written a number of articles about growing various vegetables, herbs and fruit trees.

Quick composting of leaves

Nature is currently providing us with an abundance of raw nutrients for next season’s garden in the form of leaves and grass clippings, both excellent ingredients for composting. Deep-rooted trees pull trace minerals from deep in the soil and deposit them in their leaves. Leaves contain twice as many minerals as the same weight of manure. The main problem with using leaves is that they mat and this creates a barrier to air circulation and water absorption and consequently slows the composting process or, in some cases, stops it altogether. There is an easy solution to this: mow or shred your leaves. This reduces their size and creates many leaf edges that are then easily accessible to microbes that break down the leaf structure. A rotary mower, shredder or even a whipper snipper will do the job.

To begin your compost heap, select a site directly on soil and start building layer by layer. Begin with a layer of shredded leaves about 100-150mm thick, then add 50-100mm of fresh grass clippings. By the next day, the clippings will have created considerable heat. Add some animal manure. Fermented vegetable scraps can be added next (such as the contents of a Bokashi bin – Bokashi mix is full of microbes and a scattering of this alone will speed up composting). Repeat these layers until the heap is 1-1.5 metres high and has a similar width. Make sure you water each layer as dry material will not compost. Add a ‘heavy’ layer to the surface to prevent any leaves blowing away – this could be soil, hessian bags or chicken wire. The final step is to turn your heap regularly and, as the leaves are light, this won’t be heavy work. Leave the heap for a fortnight, then turn every 3 days for rapid composting until you have a rich, black humus which you can either dig into your soil or add as a layer of mulch.

Make your own heat bed

Heat beds provide an effective way of raising seedlings and plants during the colder months. They can be made above-ground or in-ground using fresh animal manure covered with a layer of soil or sand.

The purpose of an above-ground heat bed is to raise seedlings in punnets or plants in pots where they can’t tolerate cold roots in the winter. Such a bed is best placed inside a greenhouse or in a place protected from cold air. Simply create a box using wood or bricks, or even use a polystyrene box. Fill the base with fresh, preferably steaming, animal manure, and cover with 2-4cm of sand or soil. The decomposing manure will heat the layer of soil on top. Insert your seedling punnets or potted plants a couple of centimetres into the soil layer and you have a heat bed.

In-ground heat beds in the garden are used for plants that require higher temperatures than the soil provides for root development and growth. In our climate, this would include plants such as ginger, turmeric, galangal, cantaloupe and watermelons. For example, cantaloupe seeds require a soil temperature of 21°C to germinate and thus benefit enormously from this method as they can get a head start early in the season, allowing plenty of time then to set fruit and have it ripen. Dig a trench or hole 30cm deep, add 22cm of fresh manure, cover with 8cm of a mix of soil & compost, and plant into that.

Watering errors

Recent high temperatures have highlighted that some people do not know the principles of protecting their gardens from extreme heat.

Imagine that you are a plant in a garden on a hot day. Would you prefer to be well hydrated before the heat hits or go into resuscitation mode when you are dehydrated, wilted or dying? Plants are just like us – they need to be fully hydrated before high heat and then re-hydrated afterwards. Many people make the error of watering only at the end of a hot day by which time their plants will have root damage, scorched leaves and sunburn, all of which is preventable. And just as we would wear a hat and clothing to protect our skin, plants need a protective covering of mulch around their roots and shade cloth or other covering (sheets, umbrellas etc) overhead to reduce water loss.

Under-watering is also a significant error and ultimately a significant waste of water too. Any time that a plant wilts, its roots are damaged (even if you water later and the plant seemingly recovers). Water close to the roots, directly onto the soil or mulch, or under the drip line of trees, taking into account how exposed to the sun the plant is, its size and whether it has extra water requirements. Identify which plant or plants in your garden wilt first and use this as a barometer of the dryness of your soil. Dig down and check the moisture content if you are not sure.

If you are watering a pot, it needs sufficient water to drip out the bottom which is where the roots will be. If it doesn’t drip, it is too dry. Even a small pot – say a 7cm tube which herbs are often grown in – needs at least a cup (250ml), and more if it is at all pot-bound. If you are not sure if you have watered a pot sufficiently, gently tap the plant out of the pot and check how far the water has penetrated. Often, it will be just the top centimetre or two and nowhere near the roots.

Finally, remember that it is the roots, not the leaves, which deliver water to the whole plant. The roots absorb water and channel it via the stem and branches to the leaves, flowers and fruits.

Seed saving

February and March are ideal times for seed collecting – both seed that has dried on the plant and wet seed which has to be extracted, washed and dried. Example wet seeds are tomatoes, pumpkins, zucchini, cucumber and capsicum. Consider collecting both early and late wet seed, particularly tomatoes, thereby selecting for plants that will produce both early and late in the season. Choose the best fruit, label clearly and plant at least one of each. You should be able to extend the tomato season until late May, if not early June. Note that pumpkin seed will often not grow true as it can be cross pollinated by bees from as far away as 8 kilometres (but you may get a variety of interesting pumpkins on the one vine!). You can, however, keep the seed true by either bagging the flowers or hand pollinating.

[Editor’s note: As Robin points out, you should keep back the best seed for planting, rather than follow the obvious course of eating the best and planting the dross. Incidentally, Richard Dawkins said (in The Ancestor’s Tale) that his father found this one of the hardest lessons to get across to farmers in Africa in the 1940s. If you want to know more about seed saving, an excellent book is The Seed Savers’ Handbook. Both readable and comprehensive, it would be a nice gift for anyone at $32. And here is a free booklet: A Guide to Seed Saving, Seed Stewardship & Seed Sovereignty.]

What is a compost activator?

A compost activator is a plant that activates and speeds up decomposition in the compost heap. It is the presence of potassium that makes a plant an activator. Potassium is found in sufficient quantity in the leaves of comfrey, yarrow, tansy, dandelion and stinging nettle and so you should put as much as you can of any of these in your compost layers. Comfrey also adds good quantities of trace elements which have been taken up by their very deep roots and deposited in the leaves, which then easily break down in the compost, releasing these trace minerals.

At this time of year, and during the hotter months to come, make sure that your compost is always moist throughout – decomposition will grind to a halt without moisture. Also at this time of year, there are plenty of fresh grass clippings available – add these clippings to speed up, and heat up, your heap, thereby killing any seeds that you have incorporated.

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