Honey locust trees in Christopher Columbus Park near Long Wharf have already started to turn. A good number of their leaflets were yellow this afternoon. Most of the honey locust trees in the city are still green, but probably not for too long.
I found this white-dotted prominent caterpillar (Nadata gibbosa) crawling across Meadow Road yesterday. A green caterpillar with an opaque, lighter green face, it is covered with white dots. This one had two brown patches on it, perhaps some sort of infection?
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On Sunday, Jef led a small group of us on an urban nature walk. We started at the Bussey Brook Meadow and moved on to the Arnold Arboretum, ending at the Forest Hills gate. Mosquitoes hounded us, especially in the Meadow.
Jef called the meadow a European wildflower garden. We saw some periwinkle-colored chicory flowers (Cichorium intybus) and bird’s-foot trefoil flowers (Lotus corniculatus) with orange streaks on bright yellow. These were among the many wildflowers native to Europe.
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I took photos of a wealth of natural life at the Arnold Arboretum yesterday. Among the birds, dragonflies, frogs, and plants, only one of the subjects was accessioned: Wilson’s spiraea (Spiraea wilsonii).
Black locust trees (Robinia pseudoacacia) are an invasive species in Massachusetts, but it is difficult to dislike them this time of year, when the trees perfume the air with a jasmine-like scent. The trees can no longer be legally planted. Older trees can be found in yards, but most of these trees grow in minimally-maintained spaces.
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For populations to evolve, mutations are necessary. These changes in the genetic code often go unnoticed but, when they do affect the plant’s development, horticulturists select for the ones that make plants more productive or pleasing to people. In Tuesday’s tree mob, the Director of the Arnold Arboretum Ned Friedman spoke to us about a clearly visible mutation in an eastern redbud tree close to the katsura collection (accession #10-68*B).
Friedman first introduced the botanical term “cauliflory,” a reference to plants that flower from old growth. Redbud is one of these plants. See the photo below for flower buds on the trunk of the tree.
Friedman then pointed out that one branch of the redbud tree had white flowers, in contrast to the reddish-purple flowers on the rest of the tree. Because eastern redbud flowers on old growth, he was able to pinpoint the location on the branch where the mutation knocking out the anthocyanin pigment in the flowers must have occurred. He guessed that the mutation occurred between ten and twelve years ago.
Friedman said that the mutation exists in every cell from that point on the branch onward and, as long as the flowers don’t cross-pollinate with reddish-purple flowers, will be seen in any plants grown from the seeds that develop on the branch.
This tree mob was the first in a series of three tree mobs that Friedman will lead on mutations in plants.
Update: “Mutants in Our Midst” article (pdf) on Arnoldia