Fall Colours

Day 8: It's not a spectacular year for colour here in the mountains. Reds and oranges aren't as vivid as they might be, and yellows lack something in enthusiasm as well. Nevertheless, these little spots of beauty draw the eye and brighten the landscape in one last grand performance before the greys and browns of winter take the stage. My vining hydrangea (left) has fully recovered from an unfortunate encounter with a lawn mower a few years ago, and now covers its trellis on the garage wall, in full view from the kitchen window. The vine maples at the edge of the yard (middle) and across the street are blushing, and even compete with their larger Big-leaf cousin (right) for Best of Show. Nature schools us in the beauty of diversity, if only we will heed her lesson and open our eyes to the wonder of it.

True Colours

Day 5: With the onset of Autumn, trees and shrubs reveal their true colours. Yes, you read that right. Now, shorter days and cooler temperatures slow down the flow of nourishing carbohydrates and chlorophyll production is reduced. As existing chlorophyll breaks down, the natural colours of the leaves are no longer obscured by green and begin to shine through in all their glory. Eventually, a hard abscission layer is formed where petiole meets twig and, generally speaking, the leaf drops. Deciduous trees and shrubs are not all alike in the types of pigments present in their leaves. Those which turn red in Fall are long on anthocyanins. Large amounts of xanthophyll are present in those which turn yellow. Leaves which turn orange contain carotene. These pigments are not immune to shorter periods of sunlight and colder temps, though, and eventually even they will succumb and turn brown. Some leaves may hang on until the following spring. This phenomenon is called marcescence, and it will be the subject of a future post.

Pigmentation

Day 19: Why do leaves change colour in autumn? As you already know, leaves contain chlorophyll, the substance which allows them to convert carbon dioxide into the starches and sugars which are their food. Sunlight and warmth encourage the production of chlorophyll, and in the autumn, this process slows down as temperatures begin to dip and even more specifically, to length of day. As nights grow longer, thicker cells form near the juncture of leaf and stem (technically, this is the "abscission layer"), blocking the transport of carbohydrates. Evenutally, this will be the point from which the leaf falls. As the chlorophyll in the body of the leaf breaks down in response to the decrease of carbs, pigments such as anthocyanin (red), xanthophyll (yellow) and carotene (orange) are quite literally unmasked, no longer obscured by an abundance of chlorophyll. After a freeze, these pigments also deteriorate until no pigment remains but brown tannins. Various external conditions can affect the intensity of colour, such as lack of water, steady low-range temperatures above the freezing point, or a hard frost. The amount of each of these pigments in the leaves is responsible for the hues typically seen in certain species, and of course gives each geographic area its own unique character.

October Wow

Day 358: Wow! "Mount Wow," that is. The name was derived from a native-language word meaning "mountain goat," and applies to a massif on the western boundary of the Park which is prime goat habitat. Foreshortened here by my proximity to the trees, Mount Wow rises abruptly to 5921' from the Westside Road and has been the source of many damaging rockfalls. The constant scouring of its slopes by rock and avalanche keeps vegetation at a minimum with the exception of dense groves of pioneering vine maple (Acer circinatum). If Mount Wow's towering face wasn't enough to make you say "Wow!" then the maples in a "red year" such as this certainly would.

"Red years" only occur when certain climatological criteria are met, and what those criteria are remains a mystery to me. Prolonged dryness is one factor, but by itself, it is not enough to trigger a red year. Sometimes after a summer drought, I have seen these trees go from sickly yellow directly to dead brown. On other occasions, they transition through a feeble pink without ever achieving their full red potential. Nor is it cyclic, although glorious, full-blown red years occur roughly one in five. This year, the slopes of Mount Wow are aflame with maple fire, a delight for the eyes even in the absence of goats.

Fall Colour

Day 355: I half-expected to see little pockets of frost in the yard when I stepped out onto the back porch and felt the chill in the morning, but if it was there, it eluded my eye. That said, a few things are starting to colour up and seed pods are bursting, ready to be harvested for next year's planting. Autumn is not the end, but rather the beginning of a new gardening season, the time when potential is paramount in the gardener's mind. It is a time of evaluation and planning, identifying what needs lifting, what needs moving, what might go here or there to give shade or to eliminate it. Autumn's advice must be heeded. What worked well? What did not? In pulling out the nasturtiums, I discovered that they had saved my other plants from attack by black aphids. A boon, perhaps? Or in a garden where they had only ever been a problem on marigolds, were they drawn to the nasturtiums, there to breed and lay eggs? Whatever the case, a lesson was learned under Autumn's tutelage. There will be no more nasturtiums for me!