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Until the 20th century, most home gardeners used materials that were all around them - soot as a general killer of soil bugs, soapy water to kill aphids, wood ashes to provide potash, horse manure to replenish the soil and compost to make good use of weeds and clippings.
As the car replaced the horse, gardening practices changed, not only because stable manure almost disappeared but also because, from about 1950, the by-products of petroleum were used increasingly to develop a range of "quick-fix" garden fertilisers and sprays to boost food production and kill insects and weeds.
At the same time, plant breeding focused on hybrid commercial crops that could be picked before they were ripe and sent long distances to market.
Keeping qualities and the look of fruit and vegetables were the primary considerations, with taste a distant third.
A disturbing side-effect was the virtual disappearance of many hardy old varieties which, unlike hybrids, bred true from seed saved by gardeners.
It is sobering to learn that pre-1960s vegetable varieties are now defined as "heritage".
More people are growing their own vegetables and fruit, not only to save on household bills but also because, as one young woman puts it, "You know what you're eating".
Like many others, she wants to be sure she and her family are not eating pesticide residues or artificial preservatives.
She could have added that vegetables fresh from the garden have more vitamins, as vitamins begin breaking down after harvesting, and some old varieties - the heritage apple Montys Surprise is an excellent example - have higher levels of natural anti-cancer chemicals.
Organic gardening is not just banning pesticides and artificial fertilisers but working with nature, aiming for diversity in plants to encourage useful insects and birds, recycling through composting and learning natural ways of combating problems, such as growing mustard as a green manure crop if wireworms are a pest.
Almost any herb is beneficial in keeping soil and insect pests out of the vegetable plot.
The exception is rue, which inhibits the growth of tomatoes.
Try these companion plants
Marigolds (Tagetes) produce a substance toxic to nematodes, tiny eelworms that attack the roots of many plants. They are especially useful to grow alongside potatoes in soil infested with potato cyst nematode.
Parsley encourages ladybirds, so grow it beside brassicas (cauliflowers and cabbages) so the ladybirds can reduce aphid problems.
Pyrethrum (Chrysanthemum cinerariifolia) beside brassicas kills aphids. The toxin is in the white daisy-like flowers.
Feverfew (Tanacetum parthenium) is an alternative.
Tobacco plant (Nicotiana alata) will keep whitefly off tomatoes, as will marigolds (Tagetes). Both grow much larger in greenhouses than in the open garden.
Alliums (garlic, leeks, onions and shallots) and many herbs seem to deter many pests, including white butterflies and carrot fly.
Nasturtiums by apple trees and beans.
In April, the Canadian province of Ontario announced plans to ban the sale and use of garden pesticides, banning more than 70 chemicals present in more than 300 products.
It would make the rules in Canada's most populous province the toughest in North America - which isn't saying much, as only Quebec has much in the way of pesticide controls.
Some plants seem to grow poorly alongside one another.
• Peas with onions or garlic.
• Brassicas and climbing beans, tomatoes or strawberries.
• Tomatoes and potatoes.
• Rue (Ruta graveolens) deters beneficial insects, so don't grow it in the middle of the vege garden.
Boil rhubarb leaves, strain and use the liquid as a spray against sucking insects (aphids and the like) and earwigs.
Garlic can be added when boiling the leaves and soap in the spray helps it to stick to plants.
Clear water will wash away spittlebugs' protective spit and enable birds to get the pests.
Soapy water sprayed on roses will kill aphids and other soft-bodied bugs.
Pyrethrum powder is made from the dried flowers of Chrysanthemum cinerariifolia and doesn't hurt mammals.
Check when buying commercial pyrethrum that the product has not had piperonyl butoxide added.