Temperatures below zero will always affect tender plants and sometimes even hardy ones during prelonged periods of cold, or if they are grown in containers. Frost and wetness at the roots can be a fatal combination.
New leaves are most prone to damage which can cause complete die-back on tender plants or kill roots – especially when wet.
Damage occurs when the water in plant cells begins to freeze and expand – damaging the cell and rupturing the cell wall. These plants become limp, blackened and often turn brown or slightly translucent. During particularly long spells of very cold weather, even hardy plants and evergreens can become damaged when soil becomes frozen and their roots are unable to take up water.
Treatment and control
If you plants are damaged by frost there is still a chance that they will survive and become healthly again, however, trying to avoid frost damage in the first place is advisable:
- Cut back frost effected stems to undamaged buds, this will encourage new growth in the spring.
- In the spring, once the risk of frost has passed, feed your plants to promote healthy growth.
- Smaller plants can be dug up and moved into a greenhouse or windowsill – often this will encourage a full recovery if the damage has not been too severe.
Try to avoid frost damage by protecting your plants when severe cold weather is forecasted:>
- Cover tender plants with horticultural fleece, straw or even newspaper to create a layer of protection.
- Where possible move smaller tender plants into a greenhouse or conservatory
- Pick varieties of plants that are less tender and have some degree of frost resistance.
- Plant tender plants in areas which offer some protection - such as against a wall, under a tree, sheltered from constant wind.
- When buying pots and containers for your patio, ensure they are frost proof to avoid cracking. These will benefit from additional insulation from fleece or bubble wrap.
- Avoid plant tender plants in frost pockets - these are the areas that are lowest in your garden where cold air will descend.
- Mulch soils with bark, manure or straw to stop it freezing, causing root damage and preventing water uptake.
- Protect the crowns (central growing point) of ferns and palms with fleece or straw. Tie the leaves together to stop snow and rain freezing in these delicate growth points.
- Plant out tender plants when all risk of frost is over at the end of May or beginning of June depending on location.
- Improve drainage of soil to prevent waterlogging.
- Don’t feed plants in winter as soft new growth is more susceptible to frost damage.