Monday was a fine day for birding at the Arboretum. Spring migrants are everywhere to be found. I managed to see seven species of warblers alone!
I saw and heard a number of catbirds, many of them hiding inside bushes. The red underneath the tail feathers caught my attention for the first time.
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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