i always think sub-tropical gardens are a bit like teenagers. While the classic English garden is, horticulturally speaking, up at 8.30am – in other words, brimming over with roses, peonies and delphiniums in May and June – the exotic garden is still pulling the duvet over its head. After a cold spring, it may still need prodding awake in mid-June.
Once up, however, it's a different story. The sub-tropical garden will keep partying late into the autumn, getting bigger and better and bolder, while the classic English version has had an early night back in July. Then, like a real-life teenager who has been nurtured through GCSEs and A-Levels, it's gone.
This makes October a very poignant time of year for those of us who have exotic plants (or, indeed, 18-year-olds). One minute you're admiring the huge glowing leaves of the red Abyssinian banana (Ensete ventricosum 'Maurelii') backlit by the late-afternoon sunshine. The next, the first frost will have transformed those leaves into a black, bat-like hulk. The knowledge that your garden won't be there for much longer makes you appreciate this last hurrah even more.
One of the most common questions I'm asked when I open my garden for the National Gardens Scheme is how I overwinter all the tender specimens. I don't have a greenhouse, a polytunnel or even a conservatory, so things have to go into the garage (cannas, dahlias), be wrapped up in a nice winter coat (the hardy bananas) or take their chance (everything else).
I'm resigned to losing the ensetes, but they grow so fast and they are now so inexpensive here in the south-east that I don't feel too guilty about treating them like annuals. I grow my cannas in pots, so the routine is straightforward. After the first real frost has blackened the foliage, I cut them down to about a couple of inches high and move the pots into the garage. Cannas are a bit like humans – in hot weather, they love water, and some varieties will even happily spend all their time in a pool, but they do not like being cold and wet.
If you grow your cannas in the ground, dig them up, dry them off and store them in compost or bark chippings. Same goes for dahlias and Eucomis comosa (pineapple lily). Some people advise turning dahlias upside down once you've chopped them back, so that any residual water in the stems can drain off. Late May is usually a safe time to take them out again.
Root-hardy bananas (Musa basjoo) can be left in the ground and some blasé Londoners don't even bother to protect them, but having suffered losses in the last horrendous winter, I'm going to wrap mine up this year. Again, the key is to keep them as dry and as frost-free as possible, but make sure you don't totally encase them in plastic or they may rot. The best solution is to make a framework around them with canes and stuff it full of straw, or bracken, or whatever is cheapest and nearest to hand. A plastic "hat" of some kind stops rain or snow getting down into the stem and freezing.
I have a huge tree fern, Dicksonia antarctica, and two or three Tetrapanax papyrifer 'Rex', but I don't usually bother to protect them at all. Admittedly, I live in London and my garden faces south-west, but I've come to the conclusion that it's the vast sheds, studios and other structures in neighbouring gardens that provide extra protection.
With smaller plants, such as Chlorophytum comosum (spider plant), Solenostemon scutellarioides (coleus) and their silver-leaved cousins, Plectranthus argentatus – both are members of the mint family – I usually keep one or two as houseplants through the winter from which to take cuttings.
Anyway, that's what happens in my garden. But what about those whose exotic gardens are on a grand scale? For the sub-tropical gardener, size matters. What makes plants like bananas and cannas and gingers so dramatic is their sheer scale, and when you put them together to form a jungle of jolly green giants, they become even more exciting.
If you can maintain that size instead of cutting everything down to ground level every winter, you are going to have an even more spectacular display the following year. It's really gardening as theatre, and as with any good theatrical production, a lot of behind-the-scenes work is required.
Will Giles, who has been opening his Exotic Garden in Norwich for 21 years, began the muscular task of putting his garden to bed at the end of October.
Like most exotic fanatics, Will loves pushing the boundaries on what will survive in East Anglia. They have a great phrase for this in the States: "Zonal denial". As well as cannas, bananas, brugmansias (angel's trumpets), hedychiums (gingers) and Colocasia esculenta 'Mammoth', with its huge elephant-ear leaves, Will's one-acre garden contains a lot of what most people would consider houseplants: bromeliads, monstera, tradescantia and the indispensable spider plants, which look wonderful cascading from tubs or hanging baskets.
Most of these tender plants go into his own polytunnels, but his ensetes are now too big to overwinter in those. Instead, he takes them to the grounds of Norwich Cathedral, where the head gardener allows him to use their huge greenhouse. Ensetes can grow 4-5ft in a year, and Will's are now 12ft. They have a high water content too, which makes them very heavy, so this is no job for wimps. You need a truck.
For Fergus Garrett, head gardener at Great Dixter in Sussex, the job of dismantling the Exotic Garden for the winter is also underway. At Dixter, they store the cannas and dahlias in the cellars and Fergus has two invaluable tips: label the plants before the frost gets them or you'll never remember which variety is which, and the expanded polystyrene boxes that fishmongers use are good for frost-free storage.
It sounds like a lot of work – and it is – but as Will points out, that's the price you pay for a garden that looks like a full-on, in-your-face piece of the Caribbean. "People do go down the route of sticking to hardy exotics, but I always feel it makes their garden look the same all year round," he observes.
That's a point: what does an exotic garden look like in winter, when it is denuded of its lush foliage and brilliant colours? "There's an evergreen framework," says Will. "There's lots of bamboo, and hardy palms like trachycarpus, and cordylines. It's much starker, but it will all survive all right."
My garden, too, has an evergreen framework and I rather like its stark simplicity after the blazing colour of summer and autumn. However, it's not impossible to keep an exotic feel all through the winter. If you look carefully around your local nursery or garden centre, you can find hardy, evergreen, even drought-tolerant plants that will provide contrast and texture. It's just a question of how you use them.
Fatsia japonica, and the hybrid Fatshedera lizei, which can be wall-trained, are a must. One of my favourites is the shrubby honeysuckle, Lonicera nitida – preferably 'Lemon Beauty', as it sprawls in a nicely jungly way. It's quite happy in a pot and its yellow foliage looks like some kind of exotic fern peeping out from alongside a fatsia or a phormium.
Another favourite is Bergenia 'Ballawley', which has huge glossy leaves twice the size of most normal bergenias. The brilliant magenta flowers in early spring are a bonus. It can be difficult to find, but the Great Dixter nursery stocks it and will do mail order.
Hebe parviflora angustifolia has spikes of white flowers in midsummer, but the main attraction is the ferny foliage, which looks wonderfully oriental alongside bamboo. I'm amazed it's not more popular as it will grow anywhere, except in a pot. It's one of the few plants I know that really seems to like dry shade.
I also have a weakness for pines, the shaggier the better. My garden is dominated by a Pinus montezumae, which has 10-inch needles, but I also have smaller ones in containers, notably the dwarf Eastern white pine, Pinus strobus 'Minima'.
I love the idea of having a totally tropical garden, but it is very tempting to have at least some things that don't need to be moved. Unless there are a couple of teenagers on hand to help out.
The Exotic Garden, Thorpe, Norwich, Norfolk NR1 4AF, exoticgarden.com, reopens on 12 June 2011 and every Sunday until 23 October; the Exotic Garden at Great Dixter, Northiam, Rye, East Sussex TN31 6PH, greatdixter.co.uk, reopens in June. Victoria Summerley's garden will be open for the National Gardens Scheme on Sunday 28 August 2011, from 2pm-6pm. Admission is £3; all proceeds to charity. Will Giles's book 'Encyclopedia of Exotic Plants for Temperate Climates' is published by Timber Press, £35.
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