Monday, May 31, 2010

A look at conifer phenology

Torrey pines (Pinus torreyana) , one of the rarest conifers in North America,
were sending out new needles in mid-January, near San Diego.

With a cool rainy Memorial Day weekend it seems like new kinds of spring wildflowers have pretty much quit coming out, and we won’t see big changes in what wildflowers are out until we finally get some warm summer days. (its 50 degrees and raining right now). But conifers on the other hand are about as active in producing new Budburst observations as they are any time of the year. So this week I thought it might be useful to do a quick review of the somewhat odd phenology stages of this ancient plant group.

Conifers are pretty interesting group of plants. The conifers were some of the first plants to grow on land, going all the way back to the Carboniferous period more than 300 million years ago, or more than three times as old as as even the most ancient groups of flowering plants that we see today. So does this mean these are “living fossils” and on their way to extinction? Hardly! Conifers despite their long history are amazingly adaptable, and actually have greatly expanded their dominance in many places, thanks to the value people place on the many wood products (or cool year around shade) that can be derived from these fast growing trees. Also these trees can handle ice, snow, wind and other events with much less injuries than broadleaved trees. Here in the West they are often the dominant species in the forest. They occur also in the East and Midwest, but in these warmer humid forests they are typically associated with poor soils, high elevations, or disturbances such as logging or fire. For more tidbits on the natural history of conifers check out books written by Aljos Farjon*

In the spring and summer we are generally looking for a couple of key stages:

First Needles: This is kind of like “budburst” or “budbreak” for flowering plants. This is when you can first see individual needles in a swelling bud

First Pollen: This is similar to “first flower” for flowering plants. The male cones or pollen cones swell, turn the mature color then one day the pollen starts flying (and hay fever season for some observers!).

Full Pollen This is when 50% or more of the branches are dispersing pollen. It often happens within a few days of first pollen.

These stages look a little different depending on which kind of conifer you are looking at. So this year I took some photos of several different kinds. For those of you that live in an area where there are not a lot of native conifers, as in many parts of the Midwest and east, you can also look at shade trees and ornamentals. Since the same species are planted all over the country these can be really interesting and valuable ones to watch, especially if they are growing away from concrete or buildings (like in parks or parkways or a backyard).

Douglas-fir. This is one of the world’s most important trees for timber, and is also one of the most common ornamental trees, so this is a really important species to observe for Budburst. In our area these are always the first to disperse pollen, but are much later in sending out new needles. As you can see in this photo they usually turn bright red just before they disperse pollen. Most pollen cones (male cones) of conifers have bright colors just before they are ripe.

Spruces. These are one of the most poplar ornamental trees in the country. The most common species are the Colorado Blue spruce, Engelmann spruce (native to the West and Northwest), Norway spruce (with the largest cones) and white spruce (native to Alaska and most northern countries). They generally disperse pollen after the hemlocks in our area and send out their needles about the same time as they disperse pollen. Spruces generally have reddish pollen cones which then turn yellow or brown when they disperse pollen. All of the spruce species in our area actually have a "cap" of scales at the tip of the bud when they reach the first needles

Soon afterwar
ds as the needles grow the cap of scales falls off.

Pines. These are some of the most common conifers across the country. They have a more unusual pattern of development, depending on how fast or young they are. Instead of just having needles emerge from buds formed during the previous year they often form “candles” which are new twigs or stems, usually covered with new needles. Like the other conifers the “new needle” stage is defined by when you can see new individual needles. This usually means that you will see the needles emerging from the tips of scale-covered bundles, usually after the candles have formed.

Pines are generally the last group of conifers to disperse pollen and send out new needles in our area. Most of them have pollen cones attached just below the clusters of new needles at the tip of the branches, as in the white pine pictured above. Ponderosa pine also looks like this. In our area the northern European pine, Scots pine (Pinus sylvestris) is usually first to disperse pollen, then ponderosa pine, then finally bristlecone and foxtail pines are the last to pollinate, sometime in early summer.

Some pines like this Scots pine pictured to the left can develop long columns of pollen cones which look a little bit like a stem or needle candle. But the key difference is the color and shape. These are yellowish in color and rounded (as contrasted with the narrow pointed shapes of young developing clusters of needles. These just started pollinating today in my yard. New needles will emerge much later.

So there you have it. The spring stages are pretty easy to see on these trees as long as you know where to look, and as long as you choose a tree that has branches that droop down low, making it easier to see what is going on! Otherwise a good pair of binoculars may be needed to see when things are happening. Since conifers are so widely distributed data from them can be really valuable for phenology scientists. If you have not looked at the phenology of local conifers, give it a try. They can help provide you a whole new perspective on spring!

Look at all this pollen! This Scots pine is producing a lot of cones this year.
Conifers vary a lot in how many cones they produce each year. They usually have a
"big year" every 5-7 years.

Paul Alaback

*Alijos Barjon 2008. A Natural History of Conifers. Timber Press. Portland.

All photos by Paul Alaback, taken mostly in western Montana and at Torrey Pines Reserve, near San Diego.

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