Perennials in Containers Require Winter Protection
Plant roots are vulnerable to freezing in containers, where the soil hardens more than it would in the ground. Stems and branches — particularly those on small trees and shrubs — need protection from the deep chill as well as from snow and ice.
Containers should be cared for to prevent splintering and crumbling.
Leonard Perry, an extension horticulturist with the University of Vermont opines that, “The most important thing you can do when overwintering container plants is ensure that they’re vigorous and established.”
“Young plants that you just pop into a pot and haven’t rooted yet may not do so well. The healthier they are going in, the better their chances,” Perry says.
Perennials should survive long periods of extreme cold if given pre-season care. That includes:
Slow-release fertilizers applied before the first killing frosts arrive boost plant hardiness. Feeding should end once the plants go dormant. With good fertility, you don’t have as many overwintering problems.
Soils must be moist when the perennials are stored to help protect the roots.
Trim and dispose of all foliage after the plants go completely dormant. That keeps slugs and other insects from laying eggs in the residue.
Bury pots — plants and all — for improved insulation. Add a layer of mulch. Unearth and return them to their usual sites the following spring.
Anything from evergreen boughs to blankets, straw to shredded bark can be used to safeguard pots and their contents. Securing a piece of Bubble Wrap or burlap around the pots also helps. Be quick to remove them once the weather warms.
Move potted plants into an unheated garage, basement, greenhouse, cold frame or similar site that matches their hardiness zone. Make sure it’s a place where the temperature stays above freezing.
Some of the containers have feet for that purpose, or you can use pieces of wood. A little height lets water escape through the drain holes and keeps the containers from splitting or cracking in freeze-thaw cycles.
Large pots seem to last longer. More soil means better insulation. Smaller pots constrict plant roots, hindering drainage.
Choose your perennials well, especially for proven longevity.
Tagged with: bubble wrap • burlap • bury pots • Containers • freezing • Indoor Gardening • Insulation • overwintering • perennials • perennials in containers • pruning • safe pots • Slow-release fertilizers • trenching • winter gardening
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