5/18/2011

Flowering Douglas-fir

Douglas-fir: branching pattern, overall form, and male/female flowers

Most of the conifers of the Pacific coastal forest are monoecious (mon-EEE-shus), meaning they have both male and female flowers on the same tree. Unlike dioecious (die-EEE-shus) trees, which have to find a date with an opposite sex tree (via the wind) before they are pollinated, many of the conifers on the coast can self-fertilize.


Female flowers will develop into seed
cones by the end of the season




Some examples of dioecious trees (male and female flowers on different trees) in the coast forest are Black Cottonwood (Populus trichocarpa) and Pacific Yew (Taxus brevifolia).






The coast has been having one of the coldest springs on record. This has delayed growth of most trees, and everything seems a few weeks behind right now. But the weather can only slow growth down, not stop it altogether.



The bright red-pink flowers of the Douglas-fir are hard to miss, and you can see the form of the finished hard, brown cone beginning to develop. Aided by the wind, the small male pollen sacks on the tree will fertilize the cones so they produce seeds.





Douglas-fir only has a good seed crop every 5 to 7 years. "Previous vegetative growth and cone crops affect the cone productivity in subsequent years and help explain the cyclic pattern of reproduction in Douglas fir." This long lived tree (up to 1500 years) does not even reach maximum seed production until trees reach old growth status, about two or three hundred years old.

Male pollen flowers
Douglas-fir seeds are a major food source for several creatures. In late July or early August squirrels frequently cut a few Douglas-fir cones and then tear them to pieces, leaving piles of cone scales. They continue their sampling until the seeds mature, then begin the harvest that will see them through to spring.

Professional cone collectors can assess a forest stand's cone maturity by watching the squirrels. When the squirrels start harvesting, so do the humans.

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