This is a blog about the native conifers of the Pacific Northwest. It is a companion to the Northwest Conifers site. The blog will focus on timely and interesting details about our conifers, their connections to the rest of the environment, and our connection to them.

Thursday, May 30, 2019

Conifers in Spring

Douglas fir
What are conifers doing in spring?  Why is it that no one notices? Well, I suspect that it is because there is too much competition from more glamorous plants like tulips and trilliums. Not even the humming birds and bees seem to pay any attention to the conifers, not that we should blame them. The conifers don’t advertise and don’t offer any nectar. Apart from the stiff competition from flowering plants, why is it that we don’t notice the growth changes of conifers in spring? I think there are primarily two reasons. One reason is that most conifers are evergreen. When deciduous trees put out new leaves the change is transformative. You can’t help but notice the difference between the naked winter branches and the burst of bright green leaves.
Conifers do put out new leaves in spring, but it’s just a little bit more of the same. You might notice that the new needles on a fir are a little brighter than the old ones, but you would be excused if you didn’t notice any difference at all. The other reason is that the “flowers” that grow on conifers are often very small. You might be looking at a branch at arm’s length and not even see them.

Grand fir
The needles on conifers don’t last forever. To maintain their status as an evergreen, the needles only have to last over a year. Most last for several years. But they generate new needles every year. You can see the buds in early spring. Each bud contains a bundle of needles. At budburst, the needles pop out in this bundle. In many conifers, the needles remain in this bundle. In others, the needles are distributed along the twig as it grows. However, not all conifers are evergreen. Some lose their needles in the fall, like most flowering trees. For example, the larches are bare all winter and burst out in a glorious display of bright green needles in the spring.
Western hemlock
Western red cedar

Most conifers develop buds during the winter. Western red cedar is an exception. New leaves just start growing at the leaf tips.

Western hemlock cones and pollen cones

The defining characteristic of conifers is that they produce cones. It is noteworthy the conifers produce two kinds of cones: The female seed cones and the male pollen cones. We are familiar with the seed cones. Some of them are quite large. However, the pollen cones are often tiny, some of them the size of a pea, some much smaller.

Western red cedar cones and pollen cones

Most conifers produce seed cones and pollen cones on the same tree. It’s no surprise that this presents a problem for the offspring, just as interbreeding does for other organisms. Conifers have developed several strategies for avoiding self-pollination, for example, growing seed cones at the top of the tree and pollen cones in the lower branches, or having pollen cones that mature at a different time from the seed cones.

Pacific silver fir pollen cones before and after pollen release
Many conifers produce pollen cones when they are young and seed cones when they are older. A few conifers, for example, all of the yews, take a more radical approach: They produce seed cones and pollen cones on separate trees, making self-pollination impossible.

Port Orford cedar cones
Even though seed cones can be quite large, in spring when pollination happens, they are quite small, sometimes no larger than the pollen cones.  As they grow, early on they develop hard woody scales that protect the seeds inside. On the other hand, pollen cones are quite delicate. They only have to last long enough to generate the pollen, which is contained in tiny sacs. When the pollen cones are mature, these sacs burst open and release the pollen.

Ponderosa pine pollen cones
Pollen in other trees is distributed mostly by insects. This explains all those colorful flower advertisements that plants create to attract the insects. Humming birds are attracted to the flowers, too. Since conifers don’t produce flowers, how does the pollen get distributed to the seed cones? The answer is wind. When the pollen cones release the pollen, the wind carries it to the seed cones. As you can imagine, this isn’t an efficient way to manage pollination. Most of the pollen never makes its way to a seed cone. This is why conifers distribute copious amounts of pollen. You can often see clouds of yellow pollen drifting from pine trees on a windy spring day. You may also see a small cloud of pollen if you reach up and tap a cluster of mature pollen cones.

See also
Conifer Pollination
Pollen Allergies