"Not enough," says Kerry Walter, who for several years headed the Threatened Plant Unit at the World Conservation Monitoring Centre in Cambridge. The database he built up provided much of the underpinning for the recently published Red List of plants that are in danger of disappearing for ever.
In the garden we would think it strange to chuck a plant on to the compost heap before we had seen what it could do for us by way of leaf, flower, fruit or scent. But that is what we are allowing to happen to plants in the wild. They are disappearing before we have even had a chance to record their potential.
Unfortunately, gardeners are part of the problem. Dr Walter quotes some grim stories about plants that have been completely stripped from their native habitats to cater to the whims of an orchid-grower or a camellia- fancier. In 1895, Carl Johnnsen wrote from Colombia to the firm that employed him as a collector. Orchids, he assured them, "are extinguished in this spot. I have finished all along the Rio Dagua where there are no plants left." To leave plants behind would be to play into the hands of rivals.
We can help by asking awkward questions about where our plants come from and how they have been produced. Traceability is a key word among those who supply food to our supermarkets. There is no reason why the principle should not apply in the nursery trade, too.
But does it matter that a plant is disappearing in the wild, if it is alive and kicking in our gardens? Yes, it does. Generally, a gardener's eye will be drawn to a clone that has bigger flowers than the norm, or brighter berries, or a more elegant habit, or better coloured foliage. A plant's appearance is what interests us. But cloning of this sort does little for genetic diversity. The plant with the bigger flowers may not have such a robust constitution as the straight species from which it has been selected. Somebody needs to care for the uglier ducklings too. They may be the redemptory swans of the future.
"Gardeners have the potential to be an enormously effective force for good," says Dr Walter, "but they must not run away with the idea that because they have one endangered plant in their back garden, they have solved the problem. Better to have it there than not have it anywhere else in the world, of course, but one plant, on its own, does not add up to the survival of a species."
So what can we do, I asked Dr Walter? Think positive, he said. "The ship may be taking in water, but it hasn't sunk yet. It's not too late to save many of these threatened plants, but salvation is more likely to come about by group effort than by individual action." A lone gardener can rarely grow enough plants in sufficient isolation to ensure that the seed will be pure.
Instead, join the National Council for the Conservation of Plants and Gardens, which has groups all over the country. Understand the importance of records. A plant without a provenance is a book with no words. Support organisations working specifically to conserve plants. Dr Walter points out that there are seven times as many threatened plants as threatened animals, but in the US, for instance, only 3 per cent of funds available for conservation is spent on plants. The rest goes on animals.
So save the camellia and think - only another 33,999 plants to go.
Send donations to Botanic Gardens Conservation International, Decanso House, 199 Kew Road, London TW9 3BW (0181-332 5953)
Ten Garden Plants in Danger in the Wild
Abeliophyllum distichum: Known only in Korea, where it has a limited natural range. A slow-growing shrub, related to the forsythia family. The February flowers are white, tinged with pink. Not showy, but scented. Does best in sun. Endangered in the wild but available from Burncoose & South Down Nurseries, Gwennap, Redruth, Cornwall TR16 6BJ (1209 861112).
Berberidopsis corallina (coral plant): Native of Chile, where commercial forestry threatens its habitats. A beautiful, evergreen, twining climber, not reliably hardy, with dark, leathery leaves and hanging clusters of deep red flowers from summer through to autumn. Needs shelter and almost complete shade. Endangered in the wild but available from PW Plants, Sunnyside, Heath Road, Kenninghall, Norfolk NR16 2DS (01953 888212).
Camellia reticulata: Introduced to this country from China in 1820, and since over-collected by zealous plant-hunters. A spectacular wall shrub in the milder counties of Britain. Large flowers of soft rose-crimson among the evergreen leaves. Vulnerable in the wild, but available from Greenway Gardens, Churston Ferrers, Brixham, Devon TQ5 0ES (01803 842382).
Clianthus puniceus (lobster claw): A New Zealand native, but the introduction of sheep and cattle to the islands has pushed its survival to the limit. Handsome, but tender and (except in the mildest areas) suitable only for conservatories. Fine, pinnate foliage and clusters of large, scarlet flowers, curved like a parrot's beak. Endangered in the wild, but available from The Conservatory, Gomshall Gallery, Gomshall, Surrey GU5 9LB (01483 203019).
Cosmos atrosanguineus: Once a native of Mexico, now a darling of the herbaceous border, with its dark maroon-crimson flowers famously smelling of chocolate. By nature perennial, growing to about 2ft. As with dahlias, its tubers will need protection to survive the winter. Thought to be extinct in the wild, but still available from Michael Wickenden, Cally Gardens, Gatehouse of Fleet, Castle Douglas, Scotland DG7 2DJ. Fax: 01557 815029 (no phone).
Kirengeshoma palmata: The roots of this handsome perennial are a valued ingredient of traditional medicine in China and Japan and it has suffered as a result. Boasts fine lobed leaves with creamy yellow shuttlecock flowers in late summer and autumn. Prefers light shade and moist, lime-free soil. It is rare in its native habitats, but is available from Holden Clough Nursery, Holden, Bolton-by-Bowland, Clitheroe, Lancs BB7 4PF (01200 447615).
Lotus berthelotii (coral gem): Common in containers and hanging baskets, but threatened in its native Canary Islands where it has been over-collected for the trade. A perennial, usually used as an annual, with long, hanging stems covered with fine, silvery foliage. Clusters of dark reddish-brown flowers in late summer. Endangered in the wild, but available from most garden centres or Church Hill Cottage Gardens, Charing Heath, Ashford, Kent TN27 0BU (01233 712522).
Magnolia wilsonii: Under pressure, as the bark is regularly harvested for medicinal use in its native China. Deciduous tree or shrub of slender growth (to 25ft) and hanging white flowers in June. Best in partial shade. Unable to regenerate easily in the wild, thus vulnerable, but available from Norfields, Lower Meend, St Briavels, Gloucs GL15 6RW. Tel: 01594 530134.
Paeonia cambessedesii: Once common in Spain and Majorca, where its habitats have been overrun by tourist development. Low growing (18in) perennial with wonderful leaves, pewter suffused with purplish-red. Deep rose-pink flowers in mid-spring. Now rare in the wild, but available from the Monocot Nursery, Jacklands, Jacklands Bridge, Tickenham, Clevedon, Avon BS21 6SG (01275 810394).
Rhododendron rex, subspecies fictolacteum: Native of south-west China where many of its natural habitats are disappearing. One of the hardiest of the large-leaved species, reaching more than 20ft where it is happy. Its creamy white flowers are blotched with crimson. Vulnerable in the wild, but available from Glendoick Gardens, Glencarse, Perth, Scotland PH2 7NS (01738 860205).