Buds: Spanning the Seasons

The sign in the window, which read, “Clearance! Hats and Gloves 50% off,” puzzled me. Snowflakes swirled on gusty winds. The bitter cold stung my fingertips — I wondered if I should buy warmer gloves while I had the chance. Clearance? Temperatures hadn’t climbed above freezing for days; the warmth of spring was a distant dream.

Blow out your boots, or lose your wool hat in winter, and when you go looking for a replacement you are likely to find sandals and sun hats on display. I used to rail against such a setup, assigning it to an insatiable human propensity for speed, afraid that at some point we might just lap ourselves. But when I began to study trees, and learned how their growth patterns transcend traditional seasonal boundaries, I softened my stance.

I began one summer by studying leaves — long and pointed, with coarsely toothed edges, on American beech; seven or so leaflets supported by a central stalk on white ash; the finely toothed leaves of paper birch. When autumn arrived the leaves flashed brilliantly and fell, but the show wasn’t over. The seemingly bare branches displayed buds for the next year’s leaves and flowers that were, as botanist and writer Rutherford Platt described, “varied as jewelry, in all sorts of exquisite shapes and bright colors.”

On beeches, the lance-like buds were such a vibrant chestnut-brown that I wondered how I could have previously overlooked them. The brown, pointed buds of paper birches were less prominent, but no less beautiful. The rounded buds on the tips of white ash twigs reminded me of the dome on a telescope observatory.

Through buds I continued studying leaves, without waiting for spring. I discovered that inside each bud miniature leaves grow into intricate ptyxix, or folding patterns. Multiple leaves and stems are packed together to allow the greatest volume in the smallest space, a process referred to as vernation that reminds me of a hiker trying to fit weeks’ worth of gear into a backpack.

These folding patterns are so specific and varied that they warrant their own set of botanical terms. Beech leaves, for example, grow in a plicate pattern — pleated along the central rib. One theory holds that the unique leaf shape of each tree is derived, at least in part, from the need for efficient folding patterns within the bud.

Throughout winter and early spring I watched the buds swell and grow longer until they seemed ready to burst open, like racehorses at a starting gate. Buds, however, don’t just open in response to a vagrant, unseasonably warm day or early season rain. Specific criteria — exposure to cold temperatures for a cumulative, but not necessarily continuous, period of time, followed by adequate day length and an accumulation of warm weather — must be met before buds break dormancy. Species, location on the tree, genetic variation, and the weather of the previous season influence the requirements of each bud.

The buds opened like slow motion jack-in-the-boxes. Stems elongated. Miniature leaves unfolded and grew larger. The volume that grew from each tiny bud astounded me. For many species in our region, including American beech and white ash, an entire year’s new leaves and new stems often originate from this single flourish, a process called determinate growth. These trees immediately develop new buds — at first smaller than the head of a pin — that will open in subsequent years. Other species, such as paper birch, have indeterminate growth — a series of buds form and open during the growing season before the following year’s buds are produced.

With either growth form, the next year’s buds, which are completed before the leaves fall in autumn, carry the legacy of seasons past. In spring the number of leaves and the length of the shoots produced by each bud are greatly influenced by the previous summer’s environmental conditions, such as temperature and moisture levels.

The growth process of buds and leaves is a continuous cycle that blurs traditional seasonal boundaries. Planning ahead, it seems, has its advantages. This winter there is still time to find jeweled harbingers of spring along the branches. And if you just can’t wait, cut some twigs at the end of February and place them in a vase in a sunny window. You’ll get an early taste of spring.