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Japanese Pagoda Tree

Styphnolobium japonicum

There are two Japanese Pagoda trees in the Park, one each in the northwest and southwest triangles. See Wikipedia entry here.
Also called the Chinese scholar tree and Regent Scholar tree, these belong to the pea family. They are good street trees and have fragrant flowers, straight trunks, and wide crowns. Its leaves are early to spread out and late to defoliate.
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Pagoda tree in southwest triangle in July
Pagoda tree factoids:
  • a deciduous tree
  • a legume, with a seed pod similar to peas and beans
  • despite being a legume, has no nodules with nitrogen-fixing bacteria in its roots (see below)
  • bears white flowers in late summer
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Japanese Pagoda tree in northwest triangle in July 2020
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Flowers and buds on the pagoda tree in the northwest triangle on July 21, 2021.
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Japanese Pagoda tree seed pods in late September
Botany 101 Bonus
Japanese Pagoda trees are in the legume family, along with peas and beans (and the Sunburst honey locusts and redbuds in the Park, with similar pea-like seed pods). Most legumes have nodules containing bacteria in their roots. Even though our atmosphere is 80% nitrogen, plants are unable to use gaseous nitrogen to build the molecules they need for life. The bacteria in the nodules and elsewhere in the soil take the nitrogen in the air and convert it into molecules like ammonia that the plants can then use. Having the bacteria in high concentrations and close by in the nodules increases the nitrogen concentration in the soil around the roots. The bacteria benefit by having a secure home and taking carbon compounds from the plant. In the days before synthetic fertilizers, legumes like soybeans were planted in fields and then plowed under to increase the nitrogen content of the soil.
In biology there are always exceptions to general rules. The Japanese Pagoda tree is an exception in that it is a legume that has no nitrogen-fixing bacteria nodules.
Symbiosis is a relationship between organisms in which both organisms benefit. The relationship of legumes with nitrogen-fixing bacteria is another example of symbiosis, similar to that of fungi living intertwined with the roots of most trees. The fungi supply another essential element, phosphate, to the plants, and receive carbon compounds from the roots.
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Energy flows through systems, while matter is recycled. This diagram shows the nitrogen cycle.
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