Northwest Naturalist

Fall is in full swing here in Montana!

I made it up to Glacier National Park this weekend to experience some fall foliage firsthand. It was absolutely stunning!

Here’s a brief guide to foliage colors in Western Montana!

Yellow:

• Members of Salicaceae (Cottonwoods, Aspens, Poplars, Willows) and Betulaceae (Alders, Birch) dominate the yellow palate of our PNW hillsides. These species begin turning in September and their colors will persist, depending on rain and wind, until late October.
• Larch (Larix) is our only deciduous conifer in the PNW. Depending on elevation, Larch will begin turning between the first and third weeks of October.
• Bracken Fern (Pteridium aquilinum) and Thimbleberry (Rubus parviflorus) also maintain a substantial degree of yellowness early in the fall before turning pale brown in October.

Red:

• Red fall foliage in western Montana is largely restricted to the understory.
• Ericaceous shrubs such as Huckleberries (Vaccinium) change color depending on sun exposure. On exposed hillsides, they’ll be red before August, while in dense forests, they may only begin changing in October.
• Rosaceous shrubs such as Oceanspray (Holoduscus), Ninebark (Physocarpus), Spiraea, Hawthorn (Crataegus), and Rose (Rosa) also tend to go through a red phase in their color change. While some of these species appear to start early (September), most of their change will persist well into October and even November.
• Red-osier Dogwood (Cornus sericea) has an interesting color change. Here in the riparian areas of Western Montana, they appear to go through a green and maroon phase, which is quite lovely, before losing their leaves entirely. Fortunately, even after losing their leaves, these shrubs have phenomenal red stems that definitely supplement the colors of fall.
• Maple (Acer) also go through a red phase here in western Montana. These native species appear to have dropped most of their leaves by mid-October.

Species with little color change:

• I’ve noticed several dominant deciduous trees and shrubs that don’t appear to change color considerably with the seasons. Of these, Ceanothus and Symphoricarpos are the most abundant.
• Ceanothus tends to keep its green foliage throughout the year or turn straight to brown in the fall.
• Snowberries (Symphoricarpos) appear to do a variety of things, but here in western Montana, they generally drop their leaves quickly without much ado.