What do I need to do in case of harsh frost?

The thermometer suddenly goes into freezing and the garden is startled. Help it to go through this difficult time for a better start later on.

What do I need to do in case of harsh frost?

Is it Cold or harsh cold?

Frost up to -5°C, only damages the most fragile plants and most of the plants in the garden are not harmed. But as soon as temperatures go below -10°C, which is quite frequent, and below temperatures of -15°C in the coldest areas, the damage is more important. There are two reasons for this. First of all when the temperatures are low, the frost is long lasting, over a period of several days. Yet a longer period of frost goes together with more damage caused to plants. Then the harsh frost freezes the soil in its depth, getting to the roots, which are more fragile than the branches and this regardless of the plant.

What do I need to do in case of harsh frost?
Winter flowering shrubs do not suffer from cold.

The more sensitive plants

Evergreen shrubs are the most fragile, as cold wind being very dry, it dries out the leaves which do not have the possibility of getting any moisture since the soil is frozen. Camellias, Heavenly Bamboos (Nandina), Lady Banks’ Roses or the Star Jasmine (Trachelospermum) are a few examples. Therefore these plants need protecting in priority, just wrapping them in wintering fleeces is sufficient. The aim is not to protect them against the cold but to shelter from the wind and keep them in a draught less atmosphere.

What do I need to do in case of harsh frost?
Ironically, snow protects plants from cold!

Double the protections

Around the plants which already have a protective layer, reinforce this protection, by adding another layer for example, layer which you will remove after this episode of intense cold (leaving in place the initial layer of course). If you do not have additional winter fleeces close to hand, a layer of dead leaves will protect the stumps. An old sheet or a piece of carpet will do just as well as it is only a temporary solution. You can also use snow as it is an excellent insulating agent. Do not hesitate to increase the layer under fragile stumps by a few extra centimetres

What do I need to do in case of harsh frost?
Remember to protect the roots, twice rather than once!

Think about your pots!

Potted plants are a lot more vulnerable than plants growing in the soil. The roots of a potted plant are exposed to cold. Yet it is their Achilles heel. A lot of plants can wither in a long period of frost, if their roots stay frozen for too long and in an intense way. In case of a harsh frost period, think about wrapping the pots with insulating material (bubbled plastic wrapping) so that the roots do not get too cold. You can also place the pots temporarily against a wall, where it is not as cold.

What do I need to do in case of harsh frost?
A frozen plant never needs water

Watering is forbidden

During a prolonged period of frost, the foliage of evergreen plants (which keep their foliage in winter) withers. This phenomenon is normal as the tissues dry out to protect themselves from cold. Do not water. Not only the plant could not absorb the water but furthermore it would keep the earth ball in a coating of frost which would lead to a certain death!

M. Jean-Michel GROULT
Pépinières PLANFOR
1950 Route de Cère
Tel : (020).7660.0178