The Royal Botanic Garden at Kew has just sent out a press notice explaining that one in five of the world’s plants is under threat of extinction. This is a highly depressing statistic, especially because in 2002 the figure was said to be one in eight. That’s a fast rate of acceleration. The most endangered habitat is the rain forest and, as we don’t get that in Oxfordshire, inevitably there’s a feeling of impotence about how we can help our planet. Plants support many forms of life. They clean the air, and if species disappear there’s always a knock-on effect. You can’t go and make a species once it’s lost.

Gardeners feel concern about the planet more than others: they are nurturing people by nature. The adage ‘think globally and act locally’ may help to lessen our inadequacies. In our own gardens we should be planting as diversely as possible so that we are using a mixture of trees, shrubs, perennials, ferns, grasses, annuals and bulbs. Offering a full range of plants pulls in more insect life and shelters birds and small animal life. Planting densely also helps and by May your planted areas should be providing a leafy canopy with no soil showing.

You also need to strike a balance between maintaining the garden so that it looks attractive while also offering undisturbed areas where small mammals, bees and insects can take shelter and even breed. Leave leaf litter under hedges and trees if possible. Have some areas of longer grass, especially on sunny banks. Don’t put the whole garden to bed by cutting it back to expose bare earth — as our parents did. A bare garden is a harsh environment.

These guidelines are being followed in gardens owned by The National Trust. They don’t use insecticides on roses and there’s a policy of only mowing areas that really need it. You may have noticed the smart grass paths slicing through unmown areas. As a result grassland species of butterfly are increasing in the Trust’s gardens.

Try to have a succession of plants in flower from early in the year until as late as possible. At the moment I am in love with my autumn border, even in the wet windy week we have been having. The fluffy heads of Miscanthus sinensis ‘Ferner Osten’, which open a damson-pink in late August here, have now faded to a silvered mink-brown. Their colour is picking up the wine-red lollipop leaves of Cotinus coggygria ‘Royal Purple’ a shrub that keep its leaves until late. Close by, two tall plants echo the same plummy colour. Eupatorium maculatum ‘Riesenschirm’ has dark stems, whorled leaves and fluffy heads. Vernonia fasciculata, commonly called ironweed, is equally tall at over six feet. This aster relative produces rich-purple flowers — rather like small asters. This border also contains dahlias, and so far they have evaded the frost. Since the EU Pesticides Review, finalised in March 2009, there are fewer chemicals on offer and many are not as concentrated as they used to be. The onus is on the gardener to choose good plants and to grow them well. The best way to achieve this is to put your plants in the correct position so that they avoid disease. We should all think hard before using any proprietary herbicides, pesticides and slug bait.