08-July London’s Clover Secrets

Parkinson grew crimson clover Trifolium incarnatum in his. Gerard recognised there were a number of species but dismissed them, just recommending that they should be studied by “the curious”. Later, Curtis, in his ‘Flora Londoniensis’, noted a single seedling could cover ten square feet in “a summer’s travelling”.

Long ago it was noticed they remained green at the end of summer when the rest of the landscape was burnt. It was the Dutch who realised their importance in the rotation of crops. White clover was grown every four years and then ploughed into the soil to enrich it. Root nodules on the plants are capable of fixing atmospheric nitrogen, effectively making their own fertiliser. This discovery led to huge amounts of seed being imported from Holland and white clover getting its alternative name of Dutch clover.

London has probably nearly twenty different species, although only four or five are common. The rest are rare and found in an unusual range of habitats. Their English names often give a clue to their identity. Generally they like dry, sandy soils close to the sea, but in London they choose to inhabit lawns, railway sidings, cemeteries and lorry parks. The vehicles in the last habitat are probably responsible for bringing in some of the alien clovers.

July is a good time to look for them as most are in flower, with the notable exception of suffocated clover T. suffocatum which flowered earlier in the spring. It gets its name from the way in which its tiny, white flowers seem suffocated by their green sepals.

The most familiar clovers are the ubiquitous red and white clover T. pratense and T. repens respectively. Zig zag clover T. medium is also common and often confused with red clover. It has longer lower stalks, narrower leaves and more of a tendency to grow in clumps. Its so-called zig zag branching in this case is less useful as a character to mark it out.

More striking clovers include the vividly coloured crimson clover T. incarnatum, sulphur clover T. ochroleucon and the haresfoot clover T. arvense. The first two are impressive colours, but unfortunately very rare. Haresfoot clover, whose flowers look like small rabbit paws, can be found easily enough in Brompton cemetery. Rarer species may take some time to find in London, if they are found at all. These include the clustered clover T. glomeratus with its delicate clusters of pink flowers, rough clover T. scabrum which is more downy than rough, reversed clover T. resupinatum which has flowers that are upside down, subterranean clover T. subterraneum which pushes its fruits into the soil, prickly clover T. echinatum which probably originates from birdseed and burdock clover T. lappaceum which quite likely made its way from the Mediterranean on a lorry wheel.

Other alien clovers include Hungarian clover T. pannonicum, the narrowleaf crimson clover T. angustifolium and fenugreek T. ornitopodiodes. The last clover probably owes its appearance to seeds discarded by London’s cooks. Its seeds have a distinctive smell and contain a yellow colouring. It is only when they are roasted they develop the familiar ‘curry’ smell. It may well become more common as it is starting to be included in ‘pick your own salad’ seed mixtures.

Of all the alien species, alsike clover T. hybridum is probably the most common as it used to be grown as a forage crop. Lastly there are yet two more clovers that tend to be found beside the sea.

These are strawberry clover T. fragiferum which at a pinch has fruits which look like miniature strawberries and sea clover T. squamosum with its paler than usual pink flowers. It can probably still be found in one or two places along the estuary.