Some cypresses wait for fire before they let their seeds go
Many cypress species keep their seeds sealed inside cones for years, releasing them only after a fire kills the parent tree and clears the ground. One Tibetan species reaches about 102 metres, second only to the coast redwood. And genetics now suggests the American cypresses were never true Cupressus at all.
Cupressus is a genus of evergreen conifers in the family Cupressaceae, growing wild in scattered warm-temperate pockets of the Northern Hemisphere, from northwest Africa and the Middle East to the Himalayas, southern China and northern Vietnam. Most are trees or big shrubs between 5 and 40 metres tall, but Cupressus austrotibetica can reach roughly 102 metres. Adult foliage consists of tiny overlapping scales 2 to 6 millimetres long that last three to five years; seedlings under two years old carry short needles instead. The round or oval cones take 18 to 24 months to ripen after pollination.
The fire strategy explains much of the genus's ecology. In the species that use it, closed cones sit on the branches until heat kills the tree, then open to seed the burnt, empty ground. Other species simply open their cones when mature. Botanists disagree about how many species exist, with counts running from 16 to more than 25, because most populations are small and isolated and hard to rank as species, subspecies or varieties.
The bigger shake-up came from DNA. Old World cypresses, with cones of 8 to 14 blunt-ridged scales, turn out to be closer to junipers than to their American namesakes; a 2021 molecular study placed Cupressus as sister to Juniperus. The New World species, with fewer spiky scales and scattered populations on dry soils, sit nearer Xanthocyparis and have been moved to Hesperocyparis and Callitropsis. One of them, the Monterey cypress, is a parent of the fast-growing Leyland cypress so common in gardens.
People have planted cypresses around temples in Asia and in parks worldwide, so heavily that native ranges are sometimes hard to trace. Some species yield very durable timber. The name comes via Latin and Greek from Cyparissus, a youth in myth whom Apollo turned into a tree after he accidentally killed a beloved stag. Ancient Greeks held the tree sacred, and it has stood for mourning since Roman times, partly because its roots grow down rather than sideways and leave graves undisturbed. Gardeners should know its pollen is extremely allergenic, rated 10 on the OPALS scale.
Source: Cupressus
