The Homeowners Column

The Homeowners Column

Weird Weather Worries

Photo of Sandra Mason

Sandra Mason
Extension Educator, Horticulture
slmason@illinois.edu

I have to remind myself it's February and not March or April. Plants don't have the luxury of calendars or the benefit of foresight. They only "know" what they have experienced. For many plants they have decided it's time to spring ahead with spring. Tulips are emerging. Perennial flowers are starting to grow. The grass is greening.

Recently I heard that the cherry blossoms are in bloom in Washington, DC. Usually their peak bloom is April 6-15. The reporter of this abnormality said, "I hope they don't forget to bloom in April". Early blooming trees and flowers have just a certain number of flower buds. They won't put on new flower buds between now and when they normally bloom. I'm sure there will still be some flowers at the usual time, but it will be with reduced numbers. I think we will see many plants blooming early this year.

But is that a bad thing? Well it may be if you have a whole festival around when something is blooming. You can check out what's happening with the cherry blossoms at http://www.nationalcherryblossomfestival.org

Some normally early flowers such as winter aconite or snowdrops take cold weather just fine. They close up their flowers and wait for the next sunny day. Some gardeners have had snowdrops blooming for the past couple weeks. We may see spring flowering bulbs such as tulips and daffodils bloom early as well as forsythia and lilac. Early bloom is not necessarily bad. Blooming early is, however, risky business. Temperatures can vary wildly in early spring. If temperatures drop into the teens or single digits while plants are in bloom, the flowers will quickly die.

We could see more extensive damage to trees and shrubs if they break dormancy too early. As reported by Extension educator Sharon Yiesla in the "Good Gardening" newsletter, woody plants need a certain number of hours of chilling to overcome their winter dormancy. Each species varies in the number of hours needed. These chilling hours are accumulated, not in the coldest days of winter, but in the days when temperatures range between 32 and 45 degrees F. This year, according to Yiesla many of our trees and shrubs are well on their way to getting their chilling requirements met. The problem arises when the chilling requirement is met early and the leaves and flowers start to emerge from the buds earlier than normal. Once these buds begin to open, they are at the mercy of changing spring temperatures. A frost or freeze could wipe out young leaves and flowers. Fortunately healthy trees will at least releaf, even if they don't reflower.

Cold temperatures can also damage young woody stems and trunks of young trees if the plants have awakened too early. For instance a Norway maple can withstand a temperature of -30 degrees F when it's fully dormant. During the growing season, however, temperatures just below freezing can cause extensive damage such as twig dieback. Also diseased plants are more likely to get frost injury.

Ideally for better plant survival we would wish for temperatures to lower gradually over time, stay cold at relatively stable temperatures then gradually warm in the spring. That is just as likely as me becoming a ballerina. Wildly fluctuating temperatures can lead to the worst plant damage.

There really isn't much we can do to slow plant growth. Mulching can help to keep soil temperatures cold, but that's about it. You may want to throw some shredded leaves over your tulips. If flowers show color early and frigid temperatures are predicted, you may want to cut the flowers to enjoy them indoors. With woody plants over this next growing season general maintenance is best. Be especially vigilant with watering during drought periods. This year may put gardener's optimism to the test.

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