Torreya
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Torreya californica |
Torreya is a genus of conifers comprising of five or six species, treated in either the Cephalotaxaceae, or in the Taxaceae when that family is considered in a broad sense. Four are native to eastern Asia, the other two native to North America. They are small to medium sized evergreen trees reaching 5-20 m, rarely 25 m, tall.
The leaves are spirally arranged on the shoots, but twisted at the base to lie in two flat ranks; they are linear, 2-8 cm long and 3-4 mm broad, hard in texture, with a sharp spine tip.
Torreya can be either monoecious or dioecious; when monoecious, the male and female cones are often on different branches. The male (pollen) cones are 5-8 mm long, grouped in lines along the underside of a shoot. The female (seed) cones are single or grouped 2-8 together on a short stem; minute at first, they mature in about 18 months to a drupe-like structure with the single large nut-like seed 2-4 cm long surrounded by a fleshy covering, green to purple at full maturity. In some species, notably the Japanese Torreya nucifera (Kaya), the seed is edible. Natural dispersal is thought to be aided by squirrels which bury the seeds for a winter food source; any seeds left uneaten are then able to germinate.
The genus is named after the American botanist John Torrey.
Torreya californica (California Torreya) is endemic in California. It is the largest species, reaching 25 m tall.
Torreya taxifolia (Florida Torreya) has a restricted habitat within Torreya State Park, along the east bank of the Apalachicola River in the Florida Panhandle and immediate adjacent southernmost Georgia. It is an endangered species, which has suffered a major decline in numbers due to fungal disease (possibly Phytophthora). Post-glacial global warming has also been implicated in this species' decline; however, it is sold by at least one Florida nursery in Hudson, well south of its native range. It is best adapted to the cooler, moister climate found in this area during the last ice age but, due to poor dispersal abilities, has not been able to colonise further north in the post-glacial warming. Cultivated specimens are however growing very well in cooler climates in the Appalachian Mountains, in northern Georgia and at the Biltmore Gardens in Asheville, North Carolina where it is regenerating naturally. It has been proposed that the best course to save the species from extinction is to plant groves of it in these areas.
[edit] Assisted Migration for Torreya taxifolia (from Florida to S. Appalachians)
Torreya Guardians is a volunteer group of citizen-naturalists, botanists, ecologists, and landowners that has formed with the mission of finding and implementing ways outside the jurisdiction of The Endangered Species Act to use private seed stock to establish groves of Torreya taxifolia trees in the southern Appalachians and points north, such that viable seeds will then be available for rewilding this tree onto private lands far enough north and at high enough elevations to resist the diseases already brought about by global warming in its endemic habitat in Florida. The idea is that Torreya taxifolia for some reason was unable to migrate on its own back north from its "ice age pocket refuge" in northern Florida, and that "assisted migration" will thus help this species return to its traditional interglacial range in the Appalachian Mountains. The January 2007 issue of Conservation Magazine depicted Torreya taxifolia as the lead candidate for assisted migration owing to global warming.
