Northland Nature: Ash tree time in local swamps

Oct. 7—Trees of the Northland put on quite a show of colors in late September and early October. Even though we've seen the autumn arboreal attire before, we want a repeat performance. We are seldom disappointed. With the shorter daylight at this time, trees have a breakdown of the green substance chlorophyll. It will no longer be needed to produce food that had been going on all summer.

With the disappearance of this food-making material, yellow color (xanthophyll) that was present all summer, but overshadowed by green, is able to show just how common it is. Yellow leaf colors may appear on many species of trees during these weeks. Despite the abundance of yellows, we often seek out the more vibrant reds.

Red substance (anthocyanin) is different from yellow. It was not present in leaves all summer, but was recently formed from excess sugars in leaves. Since trees that have these brightest colors are often small, they tend to grow along the edges of woods or roadsides where they get plenty of sunlight. This pigment, a delight to see for us, is also useful to the tree as a form of "sunscreen," helping protect other cells within the leaves.

We tend to look for the reds, and they do stand out. Though yellows are much more common than the reds, we see scarlet colors on quite a variety of trees: red maples, red oaks (usually smaller ones), dogwoods, cherries, highbush cranberries, American hazels and the vines of Virginia creeper (woodbine) and poison ivy. Bushes and shrubs hold this color as well: raspberries, blackberries, blueberries, roses and bush-honeysuckles.

But I find that it is the small tree, sumacs, that glow the most with their bright reds. Often these little trees grow in rather large numbers along roadsides. It is not unusual that an entire growth, not just a few trees, show their red compound leaves. Indeed, it may be hard to keep our eyes on the road as we drive by.

Reds are a bright delight, but they fade earlier than yellows that linger into October until the big leaf drop of mid-month. Birches, poplars, willows, sugar maples, mountain-maples, basswoods, oaks, ironwoods, big-tooth aspens, beaked hazels and elms all give this glow show as we exit September.

The abundant quaking aspens are a bit later to take on this hue. Aspen time is usually early in October. At this time, we see how numerous the trees are. Even pines often hold yellow needles now, while swamp tamaracks glow gold a bit later in October.

But of all the yellows in the region of late September, it is the black ashes that dominate. These ashes are not particularly large and grow in wet swampy sites. They normally do not even get our attention. But now, in the Northland, where swamps are common, we note a dramatic glow of yellow in the wetlands. Unlike most local trees, ash leaves are compound — leaves and leaflets are yellow at the same time.

Growing in groups in these locations, it is hard to not notice them even if black ashes are not as big as other trees of forests, parks and yards. This wetland show does not last too long, usually only a week or two; and just as quickly, this foliage show ends. But for a couple weeks, it is ash time in the swamps.

Entering October, we start with foliated forests. Within weeks, we will experience the leaf drop as most get defoliated, but for now, we can enjoy the annual autumn attires of reds and yellows.