No love for the lady ginkgos

Washington DC Department of Urban Forestry nips stinky seeds in the bud By Liza Lester, ESA communications officer. A male Gingko biloba in Lafayette Park, flanking the White House. Credit, Liza Lester April, 2012. As an urban arboreal companion, the ginkgo has much to recommend it. Its tall branches bring welcome summer shade, the fans of its leaves turn a lovely gold in the fall, it copes well with city pollution, lives for thousands of years, and isn’t prone to disease or insect infestation. But it has a serious drawback. In the fall, mature female ginkos produce fleshy seeds (not a “fruit” in the parlance of botany, as the ginkgo is not an angiosperm, or flowering plant), and unlike cherry season, the height of ginko reproduction is not a time of celebration. The seeds drop all over city streets, smelling “like dirty socks and vomit.” Some city dwellers hate the trees so much that they are willing to cut them down rather that endure the annual mess. Rather than massacre female ginkgo trees all over the city, this week DC’s Urban Forestry Administration will spray the trees with “Shield EC” aka “Sprout Nip” aka “chlorpropham,” an herbicide that interferes with the division of plant cells during growth. Agricultural distributors typically use chlorpropham to discourage potatoes from sprouting after harvest. Buds and shoots  – anywhere the plant is actively growing – are hotspots of cell division, and the incipient ginko seed buds fall off before they can grow stinky. At least, that’s the idea. Not all customers are satisfied. Since only female trees are a problem, it would make sense to plant only male trees. But male and female trees look identical when their reproductive parts aren’t hanging out. It can be a good two decades before a tree matures and begins to produce either pollen cones or seeds. Botanist CL Lee’s argument for an X/Y sex determination scheme (like the human mechanism), pointing to a subtle chromosomal difference between the sexes, has not been confirmed in the fifty years since he proposed it. Genetics has not provided an easy solution. Although Chinese scientists have been looking for molecular signatures that would allow botanists to sex young saplings, there is no easy test as of yet. Instead, nurseries now take cuttings of mature male trees to create “clones” of the male tree, either inducing root growth, or grafting the cutting to the roots of a young tree (sometimes this backfires when the graft fails and the root stock turns out to be female, hence reports of male trees turning female). But in the meantime there are robust, mature female trees...

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Loveliest of Trees
Mar22

Loveliest of Trees

Project Budburst: Cherry Blossom Blitz kicks off in the midst of an unusually early bloom. by Liza Lester, ESA communications officer IT’S the first week of spring, and Washington DC’s Tidal Basin is rimmed with snowy petals. Thousands of cherry trees bloom along the water – a week ahead of schedule. Hurried along by a streak of 80 degree (F) days and warm nights, the trees are in full bloom, the earliest since 2000, and petals will be falling by the time the centennial Cherry Blossom Festival* starts on March 24th. Much to the distress of festival organizers. A gift from the City of Tokyo in 1912, the cherry trees have brought out their spring finery around the 4th of April, give or take a few weeks, for 100 years. But a few weeks’ give is often too much leeway for the coordination of major city events, planned months in advance. The Washingtonian reported earlier this month that the city is expecting 100s of thousands of tourists, bringing 100s of millions of dollars, to arrive for the festival. So predicting the bloom is no trivial matter. Unfortunately, predicting it more than ten days in advance is entirely luck, according the National Park Service. Cherry trees are exquisitely sensitive to the vagaries of early spring weather. “This has been a wonderful learning opportunity. If the cherry blossoms don’t show up for their very own parade, people take notice,” said Sandra Henderson, director of the National Ecological Observatory Network’s (NEON) Project BudBurst. Festival organizers have sounded considerably more morose about this lesson than Henderson in the flood of recent news reports. But they are interested in different things. Henderson doesn’t have a festival to run; she just wants to map the blossoming of your backyard cherry to latitude, longitude, and date, with the option to cross-reference it to weather and climate trends. Henderson co-founded the citizen science project in 2007 with Kayri Havens-Young of the Chicago Botanic Garden, and Carol Brewer, emeritus professor of biology at the University of Montana (and now on NEON’s board of directors, among other activities). The project collects data worldwide. They’re interested in “phenology”: the study of seasonal changes and their environmental cues. The eponymous “bud burst” of new leaves unfurling on the branches of deciduous trees is one such phenomenon, or phenophase, “but don’t let our name fool you; we’re interested in plants throughout the year,” said Henderson. It’s just that “project leaf dye-off” didn’t have quite the same enticing cache. BudBurst records the first unfolding of leaves, stages of bloom, the pale green new needles at the tips of fir trees, showers of pollen,...

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