Saturday, April 28, 2012

The Tortoise and the Hare - and the Larch

A beetle rests on a whorl of brand new larch needles (c) John Ashley
A beetle rests on a whorl of brand new larch needles
There are a lot of different greens in the north woods. But my favorite is an ephemeral green, one that's just now showing up. Nothing else in the spring forest stands out like the softly-luminous green of brand new larch needles.

While our valleys are graced with deciduous trees, like riverside cottonwoods, most of western Montana's mountainsides are blanketed with dark evergreens - lodgepole pine, Douglas fir, Ponderosa pine, grand fir and the like.  All of these conifer species drop a few old needles year-round while keeping many year's worth of needles on each branch.  In this way, they always look dark green.

From river bottom cottonwoods up to highest alpine fir, most of our trees fall neatly into one of two categories, deciduous or evergreen. Deciduous trees invest lots of nutrients into growing relatively large, thin, fragile leaves with a high surface area. Thin leaves are best at photosynthesizing sunlight, but the higher nutrient load attracts more insects and other leaf eaters.

Evergreen trees grow needles (a type of leaf) that are comparatively thicker and stronger than deciduous leaves, but with a smaller surface area. While they aren't as good at photosynthesis, these woody needles require less nutrients, and they last longer and are less tasty to leaf eaters. (Bristlecone pines - which we have none of - can keep individual needles for 40 years or more!)

Two different kinds of leaves, and two different tree strategies. Deciduous trees grow faster using expensive leaves (the "hare"), and evergreens grow slower using cheaper leaves (the "tortoise"). The former can only grow in nutrient-rich areas, while the latter can grow in both nutrient-rich and nutrient-poor areas.

And then you have the larch.

Larch trees (and cypress of the south) fit into both categories, and into neither. The larch is classified as a "deciduous evergreen" (sort of an oxymoron), or as a "semi-deciduous conifer."

In the spring, larch start growing a new set of needles that erupt in clumps of whorled green. The needles are shorter and softer than their conifer cousins. They are also somewhat better at photosynthesis. In the summer, their needles darken slightly and the trees disappear from sight, blending in with the other conifers.

In the short, crisp days of fall, larch needles turn yellow and orange, splashing bright colors across what had been a dark green mountainside. The larch trees then join their deciduous cousins by dropping their all of their needles for the winter. While most of the water is locked up as ice, the larch trees stand barren and leafless in the winter woods.  In the spring, after the birds flock back, after the insects magically reappear, and after the grayling move upstream to spawn, only then do the luminous larch needles begin showing up.

In this way, larch trees stand apart and command my attention twice a year. Spring greens and fall yellows are seasonal reminders that success can be found in the middle.