Forecast of March freeze raises fear of damage to early blooming plants

The calendar may still say winter, but unseasonably warm temperatures during February and March have convinced many blooming plants that spring has arrived.

The bad news is that the average last frost date in southwest Missouri is April 20 meaning there is lots of time left for these happy and colorful trees and flowers to get bitten back.

The news is especially disheartening for those with fruit trees that are ready to bloom according to Kelly McGowan, horticulture educator with University of Missouri Extension.

“Flowering plants are two to three weeks ahead of schedule in this area,” said McGowan. “A downside of early blooms is that they finish early or get damaged by late freezes or frosts.”

Degree of damage

It may be nice to have all of this color in February and early March, but early blooming puts flowering plants at risk of freeze damage when winter reasserts itself. Especially in southwest Missouri where the weather can be erratic.

“My advice is to enjoy it as long as it lasts, and if it freezes, we’ll deal with it,” said McGowan.

Dormancy is how plants endure winter cold. But when unseasonably warm weather causes plants to bloom early, a cold snap can bring them to an early end.

Most of the plants will probably survive a dip to just below freezing. But once the temps dip to 27 degrees Fahrenheit or lower, flowers turn to dishrags on a stick.

Plants are a lot less winter hardy when they are actively growing.

“The degree of damage is determined by how cold it gets and how long it stays cold. Other factors, like wind, may help protect plants when air temperature plummets,” said McGowan.

The wind stirs the air, mixing the air with the residual heat out of the ground. It can moderate the air temperature and protect plants.

Dealing with damage

Gardeners and homeowners can take some precautions when temperatures are forecast to drop.

One recommendation is covering plants before temperatures drop. Cardboard boxes or pots can be turned over to cover small plants, and sheets can cover larger flowerbeds or small shrubs.

Then wait until spring arrives and plants begin to grow before making any final decisions.  This is the best time to assess overall cold injury to plants.

As the plants begin to grow in the spring, prune only dead and severely damaged wood. Do not prune live wood. The larger the leaf surface area of the plant, the better it can manufacture food and grow new tissues.

If fruit plants have injured flower buds, prune less than normal to compensate.

Be sure to also water properly. Make sure the plant is not further damaged by drought. Pay special attention to evergreens and plants situated under eaves. Water properly throughout the spring, summer, and fall.

Fertilization is recommended if the soil lacks adequate amounts of basic plant nutrients.

On severely damaged fruit plants, remove as much of the developing fruit as possible to allow it to overcome the winter injury rather than produce fruit.

“The best thing you can do for your injured tree or shrub is to avoid further stress during the coming season by giving it special attention and care,” said McGowan.

For more information go online to http://extension.missouri.edu or call the horticulture hotline maintained by the Master Gardeners of Greene County from 9 a.m. to 4:30 p.m., Monday through Friday, at 417- 874-2963.