Written in mid Jan, 2010.
It’s been the coldest snap for thirty years. But while we struggled to keep warm indoors, just imagine the effect on plants and gardens.
This big freeze - surprisingly, perhaps – has been more of a blessing than a curse. And a snowy white January is a beautiful start to our new year.
For our plants, their first concern is temperature. Most won’t put on growth when it dips below about 5ºC. But this does no harm – they bide their time until the weather warms up.
Snow can fall when the air temperature is just above freezing. If it settles, it makes a cosy duvet for plants – welcome insulation from the falling temperatures.
In my garden, all the tough hardy herbs – thyme, rosemary, bay and sage – were perfectly happy. Natural oils in their leaves act as a natural antifreeze.
With snow, the main worry is weight - Knock snow off vulnerable branches. My trusty fern, for example, needed my help.
A prolonged stint of freezing temperatures will also kill off some plant pests such as aphids and certain fungal diseases.
Some friendly creatures will also perish, but it’s nature’s way of maintaining the balance. Help our birds by leaving out food and water. But let’s hope those pesky harlequin ladybirds are susceptible to the cold!
Frost and ice, however, can be a deadly enemy for tender plants. Water, of course, expands when frozen – witness the many new pot holes in our roads.
When the water in plant cells freeze it can burst or weaken cell walls – damaging or killing the plant. Rapid thawing exacerbates the problem, so early morning sun is a further threat.
Soil and compost can also freeze solid. Frozen roots are unable to draw up water - plants can keel over from thirst. The rainbow chard in my window box collapsed, but thankfully perked up when it thawed. (Don’t be tempted to douse frozen pots in hot water).
The solution is to protect plants such as tender perennials before the freezing weather hits.
Wrap pots or containers with sacking, bubble wrap, cardboard or newspaper to prevent freezing. Or move them indoors. You can also loosely wrap precious plants in horticultural fleece.
For established plants growing in the ground, protect with cloches, cold frames, fleece or even old net curtains, which allow light.
If using fleece on rows of crop, remember to remove it during the day when weather allows, giving them a breath a fresh air. The fleece can get rather soggy, so dry it out if possible.
Mulch (cover) exposed soil with cardboard, straw, manure, Mypex or sheet plastic.
Remember, it’s not over yet. We may have more frosts before May – even in London. And spring is when tender plants are most vulnerable, with their first leafy growth, blossom or fruits.
So be well prepared. Frosty weather is a then a joy, not a nuisance.