Many trees produce their flowers in elongated catkins in spring, often before the foliage expands. Most - but not all - catkin-bearing trees are wind pollinated and produce vast quantities of pollen to ensure that pollination and seed set occurs. Hazel catkins are the most familiar ....
... along with alder catkins. Alder is usually the first tree to flower in spring.
Male catkins of hornbean are smaller than those of most other trees and produced just before the leaf buds open.
Silver birch male catkins are long and slender. The female catkin, seen here just above the leaves, is much smaller and points upwards. It will produce large quantities of seeds in winter, which are important food for finches.
Silver birch tree in full flower, in April.
There are separate male and female trees of goat willow (also known as sallow). This is the female catkin, with large numbers of stigmas. After pollination it'll produce masses of downy seed in early summer. Unlike all the other trees in this post, goat willow is pollinated by insects - flies, bees and butterflies - and both male and female trees are sometimes visited by blue tits that also have a liking for nectar - so this may be the only tree species in Britain that's pollinated by birds.
Male goat willow catkins, beginning to expand their golden stamens.
A male goat willow tree in full flower in late March can light up a hedgerow - and is an important source of nectar and pollen for the first insects that emerge in spring.
Poplar catkins are seldom seen (unless you go tree-spotting with binoculars) because they are produced right at the top of mature trees, but they are often the most attractive flowers of all the wind-pollinated species. They are much stouter that catkins of other trees. The best time to look for them is after a spring gale, when they are often broken off and litter the ground under the tree.
For more information about trees click here
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