Q What are the different types of frost?

A There are three types of frost you'll often hear referred to:

Air frost is when the ambient air temperature is 0°C or lower. 

Ground frost is when ice forms on the ground but the air temperature is above 0°C.

Hoar frost is formed by the same process as dew but occurs when the surface is freezing. It creates beautiful crystals of ice.

Caption: Frost looks beautiful but can damage plants

Q What are the effects of frost on plants?

A Air frost is the most damaging to plants as the water inside the leaf cells can freeze, rupturing the cell walls. Badly affected foliage darkens and appears to have been cooked, then finally blackens. If the soil freezes, roots are unable to take up water (and they might themselves be damaged) and the plant above wilts.

Ground frost is less damaging as it only affects the outer surface of the plants.

Q What should I do if my plants are hit by frost?

A Cut off any parts of the plant that have been browned by the frost. New growth will replace these in time. Unfortunately sometimes the damage is so severe. the whole plant is killed. 

Caption: Cut off growth that has been browned by frost

Q Why do some plants flop during frost and then recover?

A Some plants, such as hellebores and Arum italicum, use this strategy as a way of beating frost.  Their cells to pump water into intracellular spaces where freezing does minimal damage. The concentration of antifreeze inside the cells rises, increasing its protection. When temperatures rise, the plants recover.

Q Are some plants more vulnerable to frost than others?

A Yes:

● Tender bedding plants Gradually acclimatise tender plants raised in a greenhouse or bought  from a garden centre to outdoor conditions by hardening them off. Keep some fleece handy in case of unexpected late frosts after they've been planted outside.
● Containers Popular container plants like fuchsias and pelargoniums are often tender perennials. If frost is predicted and you have no space under cover, stand containers in a warm sheltered spot and cover them with fleece.
● Fruit trees Fruit buds can be damaged by late frosts. In frost-prone gardens choose late-flowering apple or pear varieties or wrap small trees with fleece.
● Wall-trained fruit such as peaches, nectarines and apricots can be protected by draping a curtain of fleece in front of them.
● Buds of early-flowering shrubs, such as camellias, can be damaged by rapid thawing following a frost. Protect by draping fleece over them and avoid growing in an east-facing spot where the early-morning sun will thaw them out too quickly.
● Tender veg like tomatoes, peppers, courgettes and runner beans are best started indoors and hardened off before planting out as they can be killed by frost. Potato foliage is also vulnerable, though the tubers may resprout. Cover with cloches or fleece. Earthing up potatoes by covering the plants with soil helps protect them from frost.

Q Can I walk on the lawn if it's frosty?

A It's best not to as it will damage the grass.

Caption: Don't walk on frosty grass