Cold comfort: Which trees and shrubs will best survive a freezing British winter?
Anna Pavord offers planting tips for the coming season
Saturday 11 September 2010
"The coldest winter for nearly 30 years cost British gardeners an estimated £50 million in lost plants and flowers," said one of the newspapers earlier this summer. Really? The true cost is surely lower. Of course, it's in the growers' interest to get us to chuck away stuff and buy more. To me, though, and to many of my gardening friends, the surprise has been not how much we have lost, but how little. Patience is the key.
The cold went on a long time, but by the beginning of June, I was pretty sure that the lemon verbena (Aloysia triphylla), growing against the west wall of the house, was a goner. It's not an attractive shrub, the spikes of summer flower small, insignificant and a dirty shade of mauve. But two or three fresh leaves in a cup, doused in boiling water, make the best-ever drink. Although I've never drunk "proper" tea, I'm nuts about the verbena alternative.
It grows fast, but in an untidy way, so I started snipping off some of the pale, brittle branches, but never quite got round to heaving the whole thing out of the ground. Just as well. By the end of June, masses of new shoots were sprouting from the base of the shrub and two of the thickest branches, tied in against the wall, were also pushing out green buds.
That turned out to be the pattern with several other shrubs that at the beginning of June looked completely dead. I'd written off 10 young bay trees planted as part of an informal hedge in spring last year. They settled and grew beautifully all through 2009, but the growth, of course, was all new and soft. Although bay trees established several years previously as part of the same screen came through last winter relatively unscathed, the new trees first lost the gloss of their green, then turned entirely brown.
Only the difficulty of getting to them (they are at the top of a steep slope) stopped me hooking them out. On the day I finally scrambled up to chuck them, I noticed all had produced new green shoots from the base. But what kind of winter lies ahead? That is the key. I've planted bay in various places every year since we arrived here. If the trees can get through their first few winters, it seems they will survive pretty much anything. Bits may die back, as happened on our mophead bays, but fresh growth soon fills the gaps.
I was not so concerned by the devastated appearance of the big shrubby spurges that are important pieces of furniture on the bank. They've been cut down before. And have regenerated. The question here is, how many times can they take this treatment before they give up trying altogether? Of the three different kinds, the honey spurge (Euphorbia mellifera) has been the slowest and the most reluctant to throw up new stems. But it seeds around fairly easily. Perhaps the best strategy will be to replace old-timers with more vigorous youngsters. We have four honey spurges, each of which, at its heartiest, measures eight feet high and wide. But they need several seasons growing to get to that size – that means a succession of mild winters.
The quickest of the spurges to resprout was 'Roundway Titan' the child of E. mellifera and another big spurge, E. stygiana. It's a beauty and I'm glad that its hybrid vigour seems to include a greater ability to cope with the consequences of a long, cold winter. You'd suppose that its situation would have an effect on its survival, though that did not seem to make any difference as far as the honey spurges were concerned. All are in different places. All got equally hammered. But E. stygiana is looking good now, having, like the others, started back into growth from the base in midsummer.
So despite the gloomy predictions, our actual loss was minimal: one huge grey agave in a half barrel, much too big and spiky to move under cover. It had got through the previous few winters with no difficulty (the bigger they are, the hardier they become) but I'm not weeping for it. We had already potted up a few of the babies that live a squashed life under the bottommost leaves of the parent. They overwintered in pots in the cold frame. All the succulents survived the winter in that same completely unheated cold frame. The secret is to get them under cover while the pots are still quite dry. In winter, succulents are more likely to rot off because of damp, than shrivel because of cold.
At Great Dixter in Sussex, head gardener Fergus Garrett reports "surprisingly few losses" in the famous Exotic Garden. Solanum crispum 'Coldham' was killed, but although it's tougher than the white-flowered S. laxum, it is still considered only frost-hardy, unhappy if the temperature plunges much below -5C (23F). Which it did frequently last winter. Agapanthus, which many thought would never emerge again from the soggy mess of their melted leaves, have been flowering with all their usual deliciousness.
At the Cotswold Wildlife Park and Garden in Oxfordshire, Tim Miles grows the largest collection of tender exotics in the country, but he, too, has been cheered by some surprising survivals. "Our olive – a very old specimen – was hit back quite hard but by mid-June, I noticed it was putting out new leaf. Same with the wattle, Acacia pravissima. On the back of that warm spell we had in June, some of our palms – ones that had really been set back – began to wake up again. The Canary Island date palm (Phoenix canariensis) in the walled garden looked awful, but even that was giving us new shoots by mid-July. Some of the bananas, like Musa basjoo, lost their big trunks, but have sent up offshoots alongside. You need to give these things time, not be in too much of a hurry to condemn." I'm extremely glad (no thanks to me) those young bay trees had time to show me what they could do. It's saved me £70.
Great Dixter, Northiam, Rye, Sussex TN31 6PH is open Tues-Sun, garden 11am-5pm, house 2-5pm; admission to both £9.35, garden only £7.70. For more information go to the website at greatdixter.co.uk. The Cotswold Wildlife Park and Garden, Burford, Oxfordshire OX18 4JW is open daily (10am-6pm, last admission 4.30pm); admission £11.60. For more information go to cotswoldwildlifepark.co.uk
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