Monday, November 23, 2015

How to protect ornamental plants in winter

In anticipation of the colder weather to come, homeowners are beginning to think about how to protect their favorite shrubs and perennials from the lowest temperatures. The UGA publication "Winter protection of ornamental plants", by Extension horticulturist Robert Westerfield and horticulture professor Orville Lindstrom, explains that, with proper care during the rest of the year, many plants will take care of themselves.

They describe the process like this:  "During the late summer and early fall, the plants must prepare themselves for winter through a process called cold acclimation. This process is initiated by the cooler temperatures and shorter daylengths that naturally occur at this time of the year."

Proper care includes providing nutrients (through fertilizers) during active growth in warmer seasons, withholding excess nitrogen fertilizer in fall. Westerfield and Lindstrom explain:
"Fertilizing plants in the fall (after August or September) with a fertilizer high in nitrogen can cause a flush of new growth that is more susceptible to cold temperatures."

They add that pruning at the proper time for each type of plant is also vital, and especially to avoid pruning too late in the summer or in early fall, which, they emphasize, "can cause new growth that is more susceptible to cold injury."

Basically, most of the winter protection of ornamental plants will have been done in advance, from planting at the correct time of year, to choosing plants that are suitable for our area. If, however, a homeowner has made all the wrong moves, not knowing how best to nurture a beloved plant, or if there is concern that the local weather has not done its part in acclimatizing plants in advance of a hard freeze, Westerfield and Lindstrom offer these helpful tips:
  1. Add mulch over the surrounding soil to minimize temperature fluctuations in the soil and protect roots of tender perennials.
  2. Cover plants with sheets, blankets, or boxes, making a tent over each plant or group of plants that extends to the ground. Remove or lift covers during the day. Do not use plastic sheeting.
  3. Check ground moisture before a freeze and water if needed. They explain, "Moist soil absorbs more heat, helping to maintain an elevated temperature around the plants."
The publication "Landscape plants for Georgia", by UGA's James Midcap, Neal Weatherly, and Matthew Chappell, includes information about hardiness zones appropriate for the plants listed, which will give homeowners a better idea of the cold-tolerance of their favorite plants.

To find the best time to prune, check UGA's "Care of ornamental plants in the landscape," by Extension horticulturist Gary Wade and  Extension entomologist Beverly Sparks. This publication includes pruning information for a long list of ornamental plants.