Cold War

Tracy Wilson suggests ways to protect your plants during this erratic spring weather

24th March, 2007

This spring seems to be an almost unnecessarily cruel month in the UK. If you’re not getting battered to bits, then more importantly you’re getting caught by very late frosts. It's particularly damaging in a year like this one when we’ve had a very mild winter and we’ve got a lot of young growth going on. This morning, when I woke up, certainly the house, garden and car were a lovely shade of white. Anywhere that has a risk of being a frost-pocket is likely to get some late frosts over the next week or so. So, what can you do, and what is it most important to protect?

Most people might rush out because something’s in flower, and think ‘Ooh, must protect the flowers’. In all honesty, they’re the last thing you ought to worry about. Yes, it’s unpleasant and yes, it’s disfiguring, but it doesn’t make a dash of difference to the shrub or plant that’s out. The flowers are not important. What is important is the young growth and, in the case of planting out young vegetables, basically the whole plant because it’s very tender as no hardening up process has occurred at all. That particular material is very vulnerable. If it’s frozen, as with everything, the water in the cells swells while it freezes, it bursts the cells and the plant collapses – that’s what actually kills the plant. So you need to put in place some protection. Now if it’s something like small vegetable plants you’ve put out, if you happen to have a handy bale of straw just go out and just loosely scatter the straw on top of them. It will be enough to keep the frost off them: you’re not talking about stopping them getting cold, it’s the frost – you have to stop them from actually freezing. That will go a long way to helping them. It does help if it’s not a windy night, mind… otherwise you end up with an awful lot of straw in the neighbour’s.

The one thing you have to be careful of is horticultural fleece. It’s a wonderful invention, but unfortunately if it’s actually resting on the leaves of the plant, and the frost settles on it, the frost actually penetrates so it will freeze whatever it’s touching, although it doesn’t penetrate lower than that. If, again, you’re looking at covering small plants, I would normally recommend putting a few pea-sticks or little bits of branch out of the hedgerow, or something, along every couple of feet maybe, and draping the fleece over, so you’re making yourself a cloche, in effect. If it’s an individual shrub – cases in point at the moment would be Photinias and Pieris, which are looking absolutely gorgeous with all their brilliant red young growth coming on them, looking really fantastic – how are you going to protect it? Well, if it’s a youngster, it’s not quite so difficult, you can look again, to putting horticultural fleece around it: it’s the same principle. Either push some sticks into the top so that you can drape the fleece over and it’s not touching the foliage, or put some bamboo canes on the corners of the shrub and make a tent over the top. It’s not the sides that are really the problem, it’s the foliage on the top where the frost will settle that is the real issue. They’re probably the best two ways that you’re going to able actually to protect your plant in the garden from frost.

If it’s in a pot, OK, it might mean a hernia, but even if you just roll them into the garage overnight, it’ll make a big difference, and you can roll them out again by day. A lot of places, particularly coastal gardens, have got citrus things, like oranges and lemons, outside all the year round. If you have got one outside and it is in a pot, at the moment I’m afraid I’d be wheeling it in at night because I think the young growth will be coming on it and it’ll just be that little bit too vulnerable – you really have got to be careful. If the wind is blowing into your plot and it’s a northerly wind bringing really cold air with it, consider the wind-chill factor. When they mention wind-chill on the weather forecast that affects plants every bit as much as it affects your reddish cheeks (and mine!) and the plants will get desiccated and frozen as well, adding insult to injury. In that case, all you need to be doing is to provide a windbreak. It’s the same as a windbreak for any coastal garden, really: you’re looking at breaking the wind away from the plants. You don't need a one-hundred percent stopping of the wind, what we’re looking for is filtration. So you’re need to put up a woven netting temporary fence or consider planting a hedge or something that the wind will trickle through, so that what is coming through from the other side has basically had the stuffing taken out of it and it’s a mere zephyr of a breeze and isn’t going to do any harm at all. The hedge, or the netting, or whatever it is, will have taken the full blast of the wind. The other advantage of this is that because it filters it, it’s not like a fence which the wind will keep battering at until it falls over. Use mesh or natural hedges because the wind filters through, it’s much more forgiving – the wind isn’t coming up against an immovable object and the plants will generally be an awful lot happier.

A final thing to remember is water. Never water before a frost, because the plants will take the moisture up. The cells will then be very full, they will freeze and then split. If you’ve been planting out vegetable plants, water them earlier rather than later for two reasons, firstly so that the plants are not quite so turgid and secondly so that the foliage can dry off properly before you get the frost on them.

So, important things to remember: protect from the frost, protect from the wind, and watch when you water.

© 2007 Tracy Wilson