Your best defence against frost is to cover your plants!
You can buy special white horticultural fleece from your local garden centre. If you cannot find any, or it costs more than you expected, old bed sheets make a handy substitute. You need something light and breathable.
For row crops such as tomatoes, build a wire frame, as the plants will not tolerate the cover resting directly on them.
If frost is forecast, cover your crops first thing in the morning of the day it is expected, to prevent condensation building up under the fabric and freezing. Make sure your plants are well watered the day before the frost, so they stay hydrated throughout.
As well as protecting the foliage, you can cover the soil with a layer of straw or wood chips to help keep it warm. Your number one priority, however, should be protecting the plants themselves.
Remove all covers the next day, once the risk of frost has passed, so your plants do not suffocate.
If you notice serious frost damage despite your best efforts, unfortunately the best thing to do is cut your losses and replant.
If your plants are badly damaged, it is better to invest in new plants than wait for them to recover. If you find yourself in this situation and there is still time to replant, simply start again.
