Fifty shades of green

Plants have developed surprising ways of spreading their seed, says John Wright, as he explores the unusual and risqué manner in which some species reproduce

- John Wright

THE late-17th-century discovery of the sexual nature of plants came as a terrible shock to puritanical sensitivities, with many rejecting the idea outright on the pious grounds that God would not condone, let alone instigate, such unseemly behaviour in such beautiful creations. The 18th-century Swedish botanist Carl Linnaeus later twisted the knife with his guide to classification and identification, which relied on counting floral pistils (female) and stamens (male) and expressing the numbers in matrimonial metaphors; 'one wife with four husbands', for example. Never one to leave things alone, he also called the calyx 'the bride's bed'. However, even today, we can be startled by the thought that when we admire or sniff our garden roses, it is their sexual organs that delight us.

Perhaps plants, too, are appalled, as many have given up on the whole messy business entirely and produce only clones. Dandelions and brambles have taken to this monastic life with some enthusiasm, with more than 500 clonal species between them. Sometimes, plant celibacy proves inexplicable. A species of moss that reproduces the old-fashioned way in Britain gave up sex when it was introduced to North America. No one seems to know why. By neat contrast, Canadian pondweed moved from North America, where it happily reproduces sexually, to Europe (and beyond), where it doesn't. In this case, the plant is dioecious (separate male and female plants). The migrating plant was female and, without any males making an appearance, the entire and vast population of this now very troublesome weed is a single, vegetatively produced, female clone.