5 Frost-tolerant plants | SA Garden and Home

5 Frost-tolerant plants

TEXT AND PHOTOGRAPHS MARIANNE ALEXANDER [[email protected]]
Last updated on 1 November 2016

These five plants are frost tolerant and will work wonders in your winter garden

 

Many frost-hardy plants are deciduous and, although their sculptural qualities are welcomed in the winter garden, it’s important when choosing varieties to have a balance between those that are evergreen and those which lose their leaves. In really cold gardens, be wary of plants which burst into flower too early in the season as your display of blossoms may well be frosted. Position these and other less frost-tolerant plants where they will have some protection from the cold.

WHAT IS FROST

Frost occurs on still, cold nights when temperatures drop below freezing (0°C). This happens when water vapour, which has condensed on exposed surfaces as dew, freezes. It is seen as white crystals coating the plants. Black frost occurs on dry cold nights. Damage is generally caused when ice crystals rupture the cells of the plants.

1. CERATOSTIGMA SPP. (CHINESE PLUMBAGO)CERATOSTIGMA SPP. (CHINESE PLUMBAGO)

Whichever of the two available species of this small, neat 50–90cm-high shrub you choose to grow, you won’t be disappointed. Vivid blue flowers appear through summer, then after a cold snap, the leaves turn red. The colder the weather, the more vivid the colours.

2. BUDDLEIA SPP. (BUTTERFLY BUSHES)BUDDLEIA SPP. (BUTTERFLY BUSHES)

Most buddleias, including indigenous species like B. saligna and B. salvifolia, and particularly the exotic B. alternatifolia, are frost hardy. The named cultivars of B. davidii, boast pendulous, 30cm-long sprays of fragrant flowers in maroon, white and purple and are the most spectacular, but are less tolerant. They’re semi-deciduous in cold regions. In early spring, cut them back to 40–60cm and they’ll reshoot to a height of 1,5m or more.

3. ABELIA GRANDIFLORAABELIA GRANDIFLORA

The beauty of the glossy foliage on the arching branches of these evergreen shrubs makes them worthwhile, so the white or pink trumpet-shaped flowers that appear in summer are a bonus. These are strongly scented, especially at night and on hot days and after fading their attractive brick red calyxes remain for many weeks. With the first really cold snap the foliage often takes on a gold or bronze tinge. Remove some old woody stems from the centre of the plant each year. Rejuvenate old plants (and reduce their size) by cutting them back hard in late autumn or early spring. They reach a height of 1,75–2,5m and can be clipped to suit confined spaces.

4. ELAEAGNUS PUNGENSELAEAGNUS PUNGENS

This is one of a number of frost-hardy evergreen shrubs which can be used as a windbreak or to create a permanent backdrop, while its colourful culitvars, with their tough, golden-yellow leaves, are ideal for lighting up the garden, especially on dull days. ‘Maculata’ has golden-yellow leaves with a golden rim while ‘Variegata’ leaves have a yellow edge. Cut back long enthusiastic growth to contain the plant to 2–3m. It is thorny and its insignificant flowers are fragrant but easily overlooked.

5. MAHONIA LOMARIFOLIAMAHONIA LOMARIFOLIA

Reaching heights of 3m, the growth habit of this tall, but narrow plant resembles that of sacred bamboo (Nandina domestica). In winter, its spirals of holly-like leaves are topped with a cluster of spikes of fragrant, bright yellow flowers. These are followed by blue berries which attract birds. It will grow well in semi-shade or where it gets morning sun; don’t neglect watering it. Cut the plant back hard to rejuvenate it.

TO MINIMISE OR PREVENT FROST DAMAGE:

  • Select plants that are suitable for the area where you live.
  • Cover susceptible plants with grass, bamboo or straw wigwams, old cardboard boxes or special frost fleece on cold nights. You can also wrap hessian or a similar material around stick tepees. Keep one side open and remove the covers each morning to let in air and sun.
  • Insulate the soil with mulch. When the ground is frozen, plants are unable to take up frozen water and die of thirst. Shallow-rooted plants are the most susceptible.
  • Place a few two-litre cool drink bottles filled with water around vulnerable plants at night; these release the heat they have absorbed in the daytime. Black bottles will absorb more heat.
  • Sprinkle water on plants before the sun reaches them so they thaw slowly; cells rupture when defrosted too quickly.
  • Grow frost-tender plants in warm sheltered positions or near walls which reflect heat.
  • Avoid planting in low-lying frost pockets; frost is more prevalent in lower areas where cold air accumulates.
  • Toughen plants up by feeding them with high-potassium fertiliser in autumn; soft sappy growth, resulting from too much nitrogen, is more susceptible.

 

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