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Plant Care
Winter in the Garden

If you garden in an area with cold, frosty winters then your garden challenge is greater than for those who garden in frost-free areas.

There are advantages, of course, like being able to grow magnificent paeonies and tulips, plants that need a period of winter chill to really do well.

If you garden in a truly cold area, or even one that experiences several hard frosts each winter then you must take account of the cold season and prepare for it.

Plant Selection
The most important place to start planning for winter is with your plant selection. Plants should be chosen for their suitability to cold winter temperatures.

Typically plants that are dormant (deciduous trees and shrubs, bulbs, perennials etc.) in winter are cold hardy and plants that come from similarly cold climates.

Other plants, such as conifers, have adapted to cold weather and are frost-hardy. Annuals complete their life cycle in one season and survive cold periods as dormant seeds.

Frozen, sodden wet ground is a one of the big killers of plants in winter. Few plants can survive freezing in sodden ground and need to be in free-draining soil that is moist but not wet in winter. Wet frozen roots are the cause of many a plants' demise, and one of the reasons so many of our wonderful native plants are tough to grow in other countries.

Plants that can survive very cold temperatures once established may well succumb in a relatively mild but wet winter simply because their roots freeze. e.g. cistus, dianthus, hebe and even kowhai. To help plants through winter cold, dig organic matter and grit into the garden, improving drainage.

Well-drained soils will also warm faster in spring.

Cold winds can also kill. Wind dries plants out and when the ground is frozen roots cannot replace lost moisture from the soil.

Broadleaf trees are especially vulnerable in cold winds, and this is the reason so many cold hardy broadleaved trees are deciduous.

Conifers tend to have needle like leaves with only a small surface area, and moisture loss is contained. Many alpine plants form small hummocks close to the ground, in crevices and hollows, so that drying winds pass over them, again reducing moisture loss.

Providing windbreaks will protect plants by providing windbreaks that slow winds. Commercial windbreak cloths are tremendously effective, but not gorgeous. Hedges and trellis or batten fences will also filter and protect from winter winds.

Protecting Plants
Plant roots can still be susceptible to frost, and simply leaving some of the top growth on plants will provide frost protection - don't be too quick to cut down the border in autumn. Some perennials need more than the protection of a layer of mulch over their crown, lift these and keep them in a frost-free position such as the greenhouse or a cold frame through the winter.

Leaving some of the dead top-growth on the plant can also provide frost protection, and the seed heads will provide winter food sources for birds. If you live in a warmer, moist northern (and probably frost free!) area then removing this top growth is important to eliminate a potential site where other fungal and other problems can develop.

Some plants cannot survive cold soil, even when dormant, and we need to lift them and store in a frost free places until spring. Dahlias are not hardy in cold places and must be stored in dry-ish compost in a frost-free place.

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Winter is Cold, Make No Mistake

Winter is Cold, Make No Mistake

Cold Hardy Plants

  • Trees acer, quercus (oak), prunus, magnolias, eucryphia, fraxinus (ash), cercis, junipers, catalpa, betula (birch), podcarpus totora (totora), cornus (dogwood)
  • Shrubs viburnum, roses, corokia, pachystegia, daphne, enkianthus, hydrangea, syringia, hebe
  • Climbers clematis, vitis cognetaie (ormanental grape), wisteria, ivy (hedera), roses, humulus (hop)
  • Perennials paeonies, geraniums, delphinium, penstemon, monarda, echinaea, crambe, cynoglossum, eryngium, malva (mallow), nepeta, oenothera, primula, violas, polyanthus
  • Bulbs narcissi, trilliums, tulips, fritillaria, iris, alliums, crocus, lilium, cyclamen

Hebe topiara cold hardy unless it has 'wet feet'

Hebe topiara cold hardy unless it has 'wet feet'

Windbreak cloth - effective if not beautiful

Windbreak cloth - effective if not beautiful

Frost Heave
Frost HeaveIf you live in an area with an extreme climate, that is repeated and severe frosts, then frost heave can push your plants out of the ground. Heaving results from soil contracting and expanding as it freezes and thaws.

Autumn planted bulbs perennials and shrubs are especially vulnerable. Sunny borders are more at risk than shady corners.

One solution - apply mulch to frozen ground to keep it frozen, much like a sunscreen.

Cyclamen hederifolium braves cold winter weather

Cyclamen hederifolium braves cold winter weather

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Last revised 18 Jul '01