Berkeley Daily Planet, CA
02-20-07
Green Neighbors: Winter Native Flowers: Silk-Tassel and Leatherwood
By Joe Eaton
Along with all the flowering plums, acacias, and magnolias, a few native trees
and shrubs are late-winter bloomers. Most, like the manzanitas and flowering
currants, are on the shrubby side. But coast or wavyleaf silk-tassel (Garrya
elliptica) is a bona fide tree up to 30 feet high, showy in its own way, and
amenable to planting as an ornamental. There’s a particularly handsome silktassel specimen on the University Avenue median strip.
It’s pretty obvious why they’re called that. Both male and female flowers are
borne in catkinlike inflorescences. In the coast silk-tassel the gray-green male
catkins may be up to a foot long (in the cultivar ‘James Roof’); the silvery female
inflorescences are much shorter. Like similar flowers in other groups of plants,
they’re wind-pollinated. The leaves are somewhat manzanita-like but are paired
and have wavy margins. The fruit grows in clusters, like grapes.
The genus Garrya has 14 or 15 species, ranging from Washington State to
Panama; 6 are native to California. David Douglas first described it in 1826,
naming it for Nicholas Garry, a Hudson Bay Company administrator. Their family,
Garryaceae, is said to be one of only four plant families endemic to North
America. That was from a Stanford site, though, so I wouldn’t take it as gospel;
another source includes the Asian genus Aucuba in the family. Garryaceae in
turn is the only family in the order Garryales.
That’s this week, at least: plant taxonomy is very much in flux these days, with
new genetic studies changing a lot of the old relationships that were based on
flower structure. They broke up the lilies a couple of years ago, and I just learned
yesterday that the water lotus (Nelumbo) turns out to be related not to other
water lilies, but to proteas and sycamores. So if silk-tassels get reassigned, don’t
be too surprised.
Silk-tassels are chaparral plants, sometimes associated with conifers. Although
their glossy green leaves feel leathery, they’re browsed by mule deer and
bighorn. Native Americans treated fever, colds, digestive difficulties, and
gonorrhea with extracts from the bark; the active ingredient is an alkaloid,
garryine, whose bitter taste has inspired the name “quinine bush.” Stem extracts
were widely used against diarrhea in rural Mexico. The natural rubber guttapercha, used for temporary dental fillings, has been obtained from two Arizona
species.
Garryas were introduced into cultivation sometime in the last half of the
nineteenth century, and three species are popular as ornamentals. They’ve also
been planted for erosion control. Propagation can be either by seeds or cuttings.
Drought-resistant coast silk-tassel does best in well-drained soil and open sunny
or semi-shady locations.
You can see several species of silk-tassel in the Regional Parks Botanic Garden,
or the coast species growing wild in Huckleberry Preserve in the East Bay hills.
Huckleberry, as well as Tilden and Redwood parks, is also home to another
noteworthy winter-bloomer, western leatherwood (Dirca occidentalis), with yellow
bell-shaped flowers. The blossoms are followed by pale green elliptical leaves.
The name comes from the flexible twigs, so pliable you can tie them in knots.
Thoreau called the eastern leatherwood species “the Indian’s rope.” It’s also
known as moosewood or wicopy.
Western leatherwood is California’s only member of the daphne family,
Thymeleaceae. It’s restricted to the Bay Area, growing on wet slopes where soft
chaparral meets mixed evergreen forest in association with buckeye, madrone,
and coast live oak. Asa Gray, Darwin’s correspondent and ally, described D.
occidentalis from a specimen collected in Oakland. Recent studies by Bill
Graves of Iowa State University show that East Bay leatherwoods are
genetically distinct from North Bay and Peninsula populations. Graves has also
been looking at leatherwood’s reproductive strategies, which include asexual
spread through rhizomes. The conspicuous yellow flowers are serviced by
hummingbirds.
Eastern leatherwood has been in cultivation since 1750; I’m not sure about our
local species. One source says it likes a moist humus-rich limy soil; another
recommends shade and plenty of winter moisture. You might be able to find a
specimen at a specialized nursery or native-plant sale. Silk-tassel, more of a
known quantity horticulturally, should be more widely available.