When it comes to frost protection for plants, there are two options: either move delicate specimens into a sheltered spot, or protect plants where they’re growing. Here's how you can safeguard your garden plants and crops during winter.
Bringing plants under cover
In general, hardy plants can survive outside in winter while tender ones won't. But it's not quite as simple as that because the temperature in cities is higher than in the countryside, and the north of the UK is colder than the south. If in doubt, err on the side of caution and protect your plants.
It really helps if tender plants are grown in containers so you can bring them indoors easily. If they're in the ground you can dig them up and put them in pots to bring inside. The ideal place for tender, outdoor plants is a cool greenhouse. This will keep the frost off and the temperature above freezing, and make sure the plants get light and stay dry. This last point is really important as damp air and wet soil kill plants as often as freezing temperatures.
Airing the greenhouse on milder days and getting the air flowing will help to keep botrytis (grey mould) at bay. If you don't have a greenhouse, any place that can replicate greenhouse conditions would be suitable. Place plants by a window in a garage, shed or utility room, or near a window in an unheated stairwell, so they're in light, dry conditions with temperatures above freezing point.
Protecting plants outside
If plants can't be brought in, create a sort of duvet to keep the frost off them. Normally this is done with handfuls of straw, covered and kept in place with fleece or hessian and tied with string. Low-growing plants can just be covered up this way or you can construct a little tent out of bamboo to keep the fleece up off the ground. A wigwam made of bamboo and fleece and packed with straw can be put around small and medium tender plants.
The exact structure will depend on the size of the plant and its growing point – this is where new growth comes from. In a banana plant it's low down to the ground, while a tree fern's new growth comes from the top. These growing points need to be protected because if they're damaged, the plant will die. Therefore concentrate protection on these crucial areas, especially with larger plants.
For banana plants it's most important to protect the stem by packing it with straw and then wrapping fleece around it. One way to do this is to fold the leaves in on top of the crown and tie them down.
3 ways to protect plants from frost
Large plants with lots of leaves, such as palms, are the trickiest to deal with. You have to tie up the foliage so it forms the protection for the growing point. The top growth may get damaged but the whole plant should survive.
With tender climbers such as passionflowers, protection should be concentrated on the lower stems. Pack them with straw using canes or wire netting to keep it in place.
As with plants brought indoors, keep an eye out for dampness and rot. The straw can become waterlogged so if a wet spell is expected, put a waterproof cover over the plant – sheets of plastic will do. Make sure you don't keep them there for the whole season though as they won’t allow the plants to breathe and rot is almost guaranteed. Even with hessian or fleece, whenever the weather's mild, undo the ties, remove the straw and give the plant a good airing.
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