Tis the season for blossoming flowers and trees! The sun is out in the city and the sidewalks of the 20th street corridor are filled with nature. Ellen came by to give us the details on these delightful creatures!
If you walk down Florida Street in the spring, you may notice the sweetly scented butter-colored flowers on the street trees. These trees are native to Australia and have a variety of poetic common names including Sweetshade and Hawaiian Wedding Tree.
The scientific name, Hymenosporum flavum, reveals more. Hymen is Greek for membrane and sporum means seed, referring to winged seeds produced by the tree. Flavum is from the Latin flavus meaning yellow, referring to the flower color. Newer flowers emerge cream-colored, darkening to yellow as they age, so there is always a slight variety of color when the tree is blooming. In Australia, some varieties have red in the center of the flower. Too bad we don’t have those here!
(Photo by P. Vaughn courtesy of Australian Native Plants Society)
Sweetshade trees grow along the eastern coast of Australia (wetter than the west coast) in rainforests. Their narrow and sometimes awkward growth habit is normal. We find them planted as street and park trees in coastal California. They prefer a mild and moist climate, but they survive drier conditions, growing more slowly with less water. They really reflect their environment – trees grow very differently depending on the local conditions. Without protection from wind, they grow bent and contorted, as we see in this specimen planted in 1992 on Anza Street in the Inner Richmond district.
(Image courtesy of Google Street View.)
Sweetshades are not too common in San Francisco, but there are a lot of nice ones lining the lower part of Haight Street. The largest are on the west side of 7th Avenue just before it turns into Laguna Honda, planted in 2002. Because they are protected from wind by a building and get a lot of cool, moist fog, here we get a feel for what trees might look like in their native habitat.
By contrast, these older Sweetshades (planted in 1998) on 17th Street at Treat are much smaller, They get more wind and sun and less water, growing out of a small square in the sidewalk.
The Florida Street sweetshades are about 3 years old and although they get a lot of sun and not much fog, they have better growing conditions than on 17th and Treat. There is less wind, so they have a straighter growth habit, except for the one nearest the corner, which is tall and lanky, requiring additional support.
The Florida Street tree wells are a little larger than normal, so more water can get to the roots. Ground cover shades the soil, slowing down evaporation. For the first 2 years or so, the trees were hand-watered and given DriWater gelpacs underground. DriWater is water that is bound into a gel, which slowly breaks down over 30 days. Water does not evaporate or run off because it is released slowly, mimicking drip irrigation. This year, only the tree nearest the corner still gets DriWater, because it has been struggling. Now the trees only get supplemental water from leftover ice and any graywater that comes from washing out recycling or green bins. The struggling tree gets a little more ice than the others and it seems to be improving. We hope we can turn things around for this tree.
(Driwater gelpac and underground tube)
Take a minute and smell the flowers next time you walk by – they aren’t called Sweetshade for nothing.
Ellyn Shea is a gardener and garden coach in San Francisco. Visit her at http://www.garden-guidance.com