Cottonwood
Populus deltoides
Cottonwoods are old giants of the
prairies, where they grow along rivers and streams. They get their
name from the cottony seeds that blow about in May and June. Some
people may be allergic to the cotton in the air, but many more people
are allergic to the pollen that spreads on the wind earlier in the
spring. Like many wind-pollinated trees, cottonwoods bloom before
the leaves unfold. That way the flowers have a chance to catch the
pollen from other trees before the leaves act as a barrier. Cottonwood
flowers look more like strings of beads than blossoms. The male
flowers make heavy amounts of very light pollen. Cottonwood pollen
is so fragile that it breaks apart easily. Because of this, paleontologists
looking for fossil cottonwood pollen doubted whether they would
find any that they could recognize. Luckily, they have found some
good specimens in peat bogs, a soft type of soil that catches pollen
and preserves it for a very long time. Finding fossil pollen helps
scientists understand the history of forests.
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