Wild Side: A hard frost, late

Some insects reacted, and some insects may benefit.


When it comes to weather, every year is unique, perhaps more so on Martha’s Vineyard than in most places. And so far, at least from some perspectives, the spring of 2023 has been an unusually pleasant one. Most days in May hit a high temperature of at least 60°, and in contrast to most years, we’ve had little precipitation and relatively few of those dreadful, raw, overcast days with a north wind. Sounds idyllic, right?

But savvy gardeners were not deceived, and in fact the past month has posed interesting challenges to flora and fauna, both wild and domesticated. The nights of May 10, 15, 24, and 27 all produced localized frost on Martha’s Vineyard, with “official” temperatures at the airport dropping close to or below freezing on all those nights. Freezing temperatures were quite widespread on the night of May 24, with some locations apparently dropping well below 32° and into “hard frost” range.

This is notable. According to statistics on the National Gardening Association website, May 12 is a reasonable date to declare the Vineyard safe from frost: The chance of freezing temperatures at that date is a mere 10 percent, and declines steadily from there as the month progresses. Parts of the Island, in short, have just experienced a hard frost a full two weeks after they should have been safe.

While I’m sorry about your tomato plants, this column of course focuses on wild species. How did this quirky cold affect the natural world? I explored pretty extensively last weekend, and while one person’s random observations aren’t a rigorous sample, I do have some observations to offer.

First, it’s hard to make the case that insect populations suffered much, overall. Late May tends to be a slow point in the season under any circumstances, with early-season species done for the year, and late spring species not yet much in evidence. I noted, for instance, very few bees on several farms I visited over the past week or so, as part of a pollinator project I’m working on. But looking at my records from a year ago, I don’t find significantly higher numbers. It’s the point in the season, not the recent frosts, which are mostly to blame.

But some insects do seem to have altered their usual pattern this spring, in some cases emerging later or at least over a longer period than usual. The sleepy duskywing, for example, is an early-season butterfly of Vineyard frost bottoms and scrub oak barrens. The first individuals are usually on the wing around the third week of April, and that was the case in 2023. But most years, the emergence of this species is done by early May, and by mid-month, unworn, freshly emerged sleepy duskywings are rare. This year, however, a burst of freshly emerged individuals cropped up in frost bottoms in the third week of May. I can only assume that the quirky weather delayed the maturation of these (a reasonable and probably beneficial physiological response).

Damage to plants was also very much in evidence, with lots of wild indigo and sheep laurel blackened by late frosts. The damage, while patchy, looks grim, but I doubt it will harm the plants in the long run. They will likely produce a second flush of foliage. Moreover, the frost-damaged plants will likely bloom later than their untouched colleagues, resulting in an extended bloom period for these species. And that change may be beneficial for bees and other insects that depend on the flowers of these plants. What looks like disaster in May could turn out to be a blessing in July.

How living things respond to unseasonable freezes is not just an academic question. Months like May 2023, with one or more very late frosts, have always occurred here, but it’s possible they’ll become more common in the near future. Paradoxically, as the oceans and atmosphere warm in response to rising carbon dioxide levels, the frequency of cold extremes is predicted to increase as well. The overall increase in average temperature really means the atmosphere is becoming more energetic. That stored energy is what drives the formation and movement of weather systems, and higher levels of energy mean more dramatic extremes, in the directions of heat and cold, wet and dry.

It will be interesting to watch change unfold over the next few decades. Wild species will vary widely in how well they adapt. Some native Vineyard species will surely face extirpation as climate change exceeds their ability to accommodate late freezes, drought, or other extreme events. In particular, I worry that many specialized bees may continue emerge on their traditional schedule even as their host plants bloom earlier, or more erratically, leaving the bees with insufficient resources.

But many other species may have the resilience and flexibility to adapt smoothly, or even benefit from the changes. The net result is far beyond my ability to predict with precision, but it’s safe to bet on reduced diversity, newly emerging ecological associations, and altered seasonality for many species that are capable of it. Things will be very, very different.