Winter wonderland

Global warming? El Nino? Some combination of the two? Whatever the cause of this weird winter weather, I’ve just been trying to figure out how it will affect this year’s gardening season. Will it be blazing hot and dry, warm and wet, or completely “normal” (whatever that means)?

Whatever the summer brings, it seems likely that the insect and disease populations will flourish this year. The fungal spores that over-winter in soil and leaf litter, and the insects that over-winter as eggs or larvae in the soil or under bark must be finding this relatively warm winter much less of a survival challenge than the normally much colder temperatures. The only thing that may now make their lives more difficult would be very cold weather without an insulating snow cover. Unfortunately, those same conditions would also be hard on all of the perennials that have been basking in the warmer temperatures. This winter has been so warm up until the more normal temperatures appeared recently that I know of a rosemary plant (zone 7) that is still thriving, and, in Philadelphia, a friend has a gardenia (zone 8) planted out in her garden that was still glossy green in mid January.

While the rosemary and other tender plants may have been happy so far, life is not entirely a bed of roses in the plant kingdom. Woody plants that grow in colder areas like ours have a built-in mechanism that prevents them from breaking dormancy during a mid-winter warm spell. They need a certain number of what is called chill hours. That is, each plant requires a certain number of hours when temperatures are below 40 degrees before they will break dormancy. The chill hours for many plants have already been filled, and so some things have begun to break dormancy already, leaving them susceptible to damage if temperatures plunge.

Some of the damage to trees and shrubs from this odd weather may not be obvious for some time. The sap of some trees and shrubs has already begun to flow and there have been noticeable changes in the leaf and flower buds. Some spring bloomers have already begun to bloom, spoiling their spring display. In the event of a cold snap, that sap may freeze, causing internal damage and dieback in the spring. Leaf and flower buds may also be killed, forcing the plant to use up energy reserves producing new leaf buds. Plants that flower from buds set last summer may not flower as well, if at all.

While insects are likely to flourish, one of the gardeners’ favorite bug zappers, the bat, is having a very rough time of it this winter. The warm weather has brought some bats out of hibernation, and between their higher metabolic rate from simply being awake, and the energy expended from flying around looking for food, some may have used up too much of their precious fat reserves to survive the rest of the winter.

Sound gloomy? Time will tell. Every year in the garden is different from every other, and brings with it its own successes and challenges. I think this year is going to be one for the record books though, drawing out every bit of our skills and imagination, but, as gardeners, I’m betting we’re up to the challenge.