The prime objective in cultivating clay must be to separate the tiny particles to allow air and water to percolate through it. A good way to achieve this temporarily is to leave the surface roughly dug in autumn so that winter frosts can penetrate. This process breaks up the large masses into small pieces which are easy to work and easy for plant roots, air and water to penetrate, but unfortunately the effects are very temporary. Walking on the ground, or simply exposure to normal rainfall, soon causes it to stick together again, unless action is taken to prevent it.
The appropriate action is to incorporate some material that will keep the small lumps apart. Sharp grit is ideal and permanent, with sharp horticultural sand a good second best, but soft builder's sand or sand off a beach is useless because the grains are too rounded. The other material which should be worked in at least annually is some kind of humus (three-quarter rotted vegetable material) - home-made garden compost is ideal. This not only separates the particles of clay but also incorporates its own air, adds plant nutrients, helps to retain both water and any added fertilisers and provides a home and food for the myriad soil micro-organisms that are continuously at work converting soil minerals into forms that plant roots can absorb.
Many commercial products are available to gardeners for this purpose, but can be quite expensive, and a lucky few have access to quantities of animal manures. For the rest of us, the cheapest and best humus sources available are leaf mould and garden compost.
Leaf mould is made simply by stacking piles of fallen leaves from deciduous trees and leaving them to slowly rot for 12 to 18 months. Smaller quantities are better enclosed in a black plastic bag, and should have water added to ensure they are thoroughly soaked. "Experts" tell us that it is also necessary in this case to make some holes in the bag to admit air, but I find there is enough air trapped between the leaves to make this unnecessary. The resulting material is just about the perfect material for soil improvement, either dug in or spread on the surface as a weed-free and weed suppressing mulch.
Garden compost is almost as easy to make and matures faster. It is helpful, and not difficult, to understand the process of converting vegetable waste material into useful compost. The raw material consists of a mixture of soft, growing plant cells containing considerable quantities of water and nitrogen compounds, and tougher, usually drier more woody material from the older growth, especially twigs, bark, dried out stems of herbaceous plants, etc. Any vegetable matter, including moderate quantities of shredded cardboard and newspaper, can be included. Animal wastes such as meat and bones should be avoided, not because they won't make decent compost but because their presence will encourage unpleasant smells and scavenging animals such as rats.
For the material to rot properly it needs air, moisture and warmth to promote the rapid growth of the bacteria and fungi that do most of the work. The more woody material also needs nitrogen in compound form (that in the air is no use). Soft material such as fresh weeds, grass clippings, etc. contain all they need at first, but quickly become consolidated so as to exclude air, resulting in a slimy, smelly mess, insufficiently decomposed to be good quality compost. Woody material, on the other hand, because it consists of hard pieces, incorporates plenty of air but is short of both moisture and nitrogen. The answer is to ensure that the two types of material are well mixed together. Additional moisture will be needed in warm dry weather, but protection from excess rain is needed at colder times since too much water will exclude air, and the bacteria will drown. Insulation is also necessary in cold weather.
If you don't have enough soft material to balance the woody stuff (and this is normal, because it takes a lot of grass, etc. to provide enough nitrogen to rot shredded twigs), an activator can be used. There are proprietary mixtures available commercially for this purpose, but animal manure is ideal, especially poultry manure which is too strong to use directly on the garden. Another readily available and very effective activator, if you collect it for the purpose instead of flushing it away, is urine (described by one BBC gardening expert as "recycled beer"). Some proprietrary mixtures claim to contain the necessary bacteria, and some gardeners add soil to the heap to provide them, but in fact the normal use of weeds, etc. will contain quite sufficient bacteria and fungi without deliberately adding them.
Many different styles of container are available commercially, and various designs have been published for home-made versions. The essentials are adequate protection from drying out in hot weather, protection from excessive wet and wind in cold weather, adequate air and the right mix of material. It is also necessary for success to ensure that the container is big enough to provide sufficient heating during the early stages of decomposition. A heap less than 3 feet cube (i.e. 27 cubic feet) is not really big enough. More than 4 feet cube (64 cubic feet) will be too difficult to fill and handle for most people. The container should have provision for turning over the material once or twice during the process, so as to re-incorporate air and mix the drier, cooler material from the outside with that in the moister, warmer centre. When I have time I will describe several designs which are easily made from cheap materials.
Many people worry that by making and using compost they will be spreading weeds from seeds and persistent roots around their garden. However, few seeds or roots will survive the high temperatures generated in a well-made compost heap in its first couple of weeks. To play safe, I always leave particularly pernicious roots, such as field bindweed (Convolvulus arvensis), to dry out for a few days before putting them in the heap. If the final product is used for digging into the soil, rather than as a mulch, this also drastically reduces the germination of any remaining weed seeds. Since it is not particularly good as a mulch anyway, this is no hardship.
Handy tip: To tell a wanted plant from a weed, pull it up. If it grows again, it's a weed. [Sent in to BBC Radio 2 by a listener]
I understand that in the USA there are standard hardiness zones. In these terms I am told the whole of Britain is in zone 8 of the USDA classification. Apparently this refers to the US Department of Agriculture system, based on average annual minimum temperature. Under this system, zone 8a corresponds to 10F to 15F (-12C to -9C) and zone 8b is 15F to 20F (-9C to -7C). I don't know until I check, but I would guess we are just about on the borderline between 8a and 8b here. Of course these are just averages. In a bad winter temperatures can go much lower, night after night for weeks.
Temperatures here are not normally extremely high or low by British standards, but the variation between summer and winter is; the difference between the average summer temperature and the average winter temperature is higher in Bedfordshire than anywhere else in Britain. Average annual rainfall is about 25 inches, low by British standards.
I'm told that with the addition of plenty of grit and heavy annual dressings of organic matter it eventually becomes a very rich soil, but I wouldn't know - I've only been here 39 years!
Quite apart from having a special wildlife area, I try to minimise the use of sprays, choose plants with wildlife benefits (such as buddleia and a small patch of nettles to attract butterflies) and avoid excessive tidiness so small creatures have somewhere to hide from predators and to hibernate in winter. We have a bird table and hanging bird feeders which attract quite a variety of birds, and we also put food on the ground for those species which insist on feeding there. I intend soon to put a short account of the wildlife I have found in the garden on my wildlife page.
I'm sure there are others just as good.
In theory this difficulty is solved by the use of scientific, Latin-based names using the system devised by Linnaeus. The way this system has been developed in recent years unfortunately means it is failing to achieve this objective.
The problem seems to be that it is being used for two quite different and incompatible purposes. The application of the system in actually deciding what name shall be given to a species has been hijacked by taxonomists whose only purpose is to use it to define the relationships between species by allocating them to genera reflected in the name, attempting to keep this up to date with the latest scientific thinking, and in cases of dispute over the correct name for a genus relying purely on "who thought of it first" - the oldest name wins, regardless of how widely a particular name is used.
The serious fault in this, in my opinion, is that the objective of ease of communication of identity of a species is being totally ignored. For this purpose the prime requirement is stability. Once a name has been established in general use for a species, it should be retained permanently, regardless of changing views on which species are really related and so belong in the same genus. There is a need, therefore, for two different international systems, one for use by taxonomists, which can be safely ignored by everyone else, and one for use by the rest of the world for purposes of simply identifying which species we are talking about in an unambiguous manner. There is no harm in them both being based on the same system and having names in common, providing everyone involved with buying, selling and growing plants, and in advising about them, uses the stable system, and the taxonomists keep their unstable system to themselves. Like legal homosexuality under current British law, the taxonomists' system should be confined to "consenting adults in private"!
Garden Encyclopedia
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I haven't yet tried out most of the following sites recommended by the Consumers' Association (UK):
Gardening.com
The Gardening Launch Pad
The Teaching Garden
Internet Directory for Botany: Gardening
The Netter Page
Links at Garden Net
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Missouri Botanic Gardens
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Royal Botanic Gardens, Kew
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City Farmer's Urban Agricultural Notes
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