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Exotic Plants in a Cool Climate

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Contents

Introductory

I am fascinated by the idea of growing plants that give the impression of belonging in the tropics, despite our relatively cold climate and (possibly worse for plant survival) damp winters.

The separate page on my tiniest garden just discusses what I have actually tried and am considering doing. Here I discuss more generally the concepts involved and provide links to other sites dealing with the same subject. I will, as far as I can, also discuss some plants that I have tried, heard of or seen, and which seem possibly suitable for the purpose.

Some people reading this page seem (from messages sent to me) to be under the impression that I am growing all these plants. That is not the case. I am actually growing at present only a very small selection, just those described on the page entitled my tiniest garden (although that is admittedly somewhat out of date at present and a few more plants need adding to it).

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Hardiness

One factor many such plants have in common, not surprisingly, is marginal hardiness. The concept of hardiness is discussed in some depth, along with some measures which can be taken to help a plant's chances of surviving cold weather, on a separate page.

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Watering

Many of the plants discussed on this page require large quantities of water, which can be quite a problem if you suffer from regular hosepipe bans in dry summers, as many areas of Britain do. Some plants prefer to have their roots extending into a pond, or to grow in a permanently boggy area (Gunnera manicata is a prime example), but others would not survive the winter in such conditions, and in any case you may not be able to provide them, so an alternative method of meeting their needs must be found.

The first essential in providing for such plants comes before actually planting them, by incorporating large quantities of organic material in the soil (home made garden compost is best and cheapest, if you can make enough). Any such material used must be well rotted before use - raw sawdust, ground bark or wood chippings would starve the plants of nitrogen by using it all up during decomposition.

The second thing to do, at the time of planting, is to plant in the same hole about a foot length of standard drainpipe, so that about an inch is protruding above the soil surface. Later watering can then be poured into the pipe so the water goes straight to the roots of the plant, where it is needed, instead of on the surface where much of it will evaporate. I have found this invaluable with my Musa basjoo, which I have given about 4 gallons of water daily most of its first couple of years, pouring it straight into the pipe from a bucket, or in dry conditions simply running a hose into the top of the pipe (40 gallons straight off on one occasion, taken from one of my water butts).

This brings me to the next point - collect as much rainwater as possible from the roof of your house, shed, conservatory, garage or any other building. During wet periods you will not be able to retain more than a small proportion of what is available, unless you have a large lake to put it in, but every drop you do retain will be invaluable in time of drought. Water collected this way is free (important if your mains supply is metered, as mine is), it is suitable for lime hating plants such as rhododendrons, camellias and pieris, but it is NOT suitable for use on indoor plants because it is not sterile and can under indoor pot plant conditions introduce serious fungal and other diseases.

Each spring (in Britain - the timing depends on your climate to some extent) the soil around your plants should be coated with a thick mulch to prevent evaporation from the soil surface and to suppress weeds which will otherwise compete for moisture. It is essential that this is done when the soil is thoroughly moist, otherwise it will prevent water reaching the soil when it does rain, and so be worse than useless. Mulch should not reach quite to the stems of plants, since it can damage them. Trees and shrubs, and some perennials, often resent the extra depth of covering against the stem, which can kill some species, and many perennials will be unable to penetrate the mulch if it is put on too thickly before they emerge.

Finally, when applying water (in the absence of a buried pipe), make sure it is applied to the soil surface from as short a range as possible, rather than being sprayed into the air where much will evaporate even before landing, more will be wasted by landing too far from the plants that need it and some will damage foliage and flowers by causing scorching in bright sunlight. Watering is best done in the evening, so the plants have all night to absorb it and less will be lost to evaporation. Thick mulches should preferably be pulled aside to apply the water to the soil, and then replaced. Remember that a thorough drenching once a week is far better for the plants than a daily sprinkling, not only because more will reach their roots that way, but also because light sprinklings will encourage roots to grow near the surface where they are in greater danger of drying out.

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The Plants

The types of plant that I consider give the impression of tropics or sub-tropics come in three main categories (some belong in more than one). First, and most obviously (to me) come plants with very large, lush leaves, preferably glossy. Next are those which have spectacular flowers, not necessarily in large numbers, but with the proviso that they must not be too commonly grown in this area (e.g. dahlias, sunflowers and chrysanthemums do not qualify). The third group are those which, while not satisfying either of the other criteria, are commonly (by the layman) associated with hot climates, such as any kind of cactus, any "spiky" plant, or other plant of a type commonly grown indoors and regarded as tender. To merit inclusion in the list below, a plant must also stand a reasonable chance of surviving most normal winters in a UK garden (with a little protection if necessary), outside the very mild south west corner of the country.

Palms

Palms are one of the most obvious groups which fit both the first and third category. Unfortunately there seems to be a difference of opinion between various authorities as to the hardiness of some of them, and even as to which is the most hardy. My palm page lists some which I have seen described as hardy, with comments about their form as well as their reputed hardiness. However, the page needs updating - I have tried growing one (Phoenix canariensis) which is not listed on it!

Bamboos

I see bamboos as less exotic-looking than many people do, but some are exceptional. They are discussed on a separate bamboo page.

Other exotic looking foliage plants

Exotic looking foliage plants, in my opinion, must have large leaves, preferably but not necessarily glossy. Those other than palms and bamboos are now described on a separate foliage plant page.

Desert-looking plants

The above group of foliage plants give the impression of a sub-tropical jungle. This alternative group give the impression of a hot desert, and are in fact all extremely drought resistant. They all like very good drainage, and in some cases need some protection from winter rain. They become increasingly hardy as they age and grow larger.

Yucca gloriosa
There are several hardy species of yucca, any of which will look as if it belongs in a hot desert. They vary in size and time of flowering, but all produce a spectacular spike of hanging creamy white bells like a huge lily of the valley. This species, sometimes called Spanish dagger, is one of the biggest, and will in time develop a short trunk. The flower spike can rise to eight feet high if it can do so before the autumn frost destroys it. Like most hardy yuccas its leaves are stiff and sword shaped, and are tipped with a genuinely dangerous spine making it unsuitable for use near a path. Take care when bending near it - you could lose an eye. The plant can eventually reach as much as six feet high and across, excluding the flowers.

The variety variegata is, as the name suggests, a variegated form which is said to be slightly less hardy, although my plant has come through the last few winters with little harm. The variegation takes the form of a pale yellow stripe along the leaves. This variety is said to be less prone to producing numerous branches (which would make it look somewhat messy) after flowering, but I find it does eventually produce several suckers as well as a few branches. Suckers can be removed with a little root in spring and replanted to produce new plants.

The flowers stems of both forms can be cut off and taken indoors as a huge and spectacular cut flower if frost threatens after they have grown to full height but not yet opened.

Yucca filamentosa
This is the yucca most commonly seen in British gardens. It is similar to a young Y. gloriosa, having no trunk and not growing quite so tall. It differs also in flowering earlier in the summer, and in having white threads at the edge of the leaves.

Yucca whipplei
A small stemless yucca flowering much earlier than most. The leaves are very narrow, needle like, and the whole plant does not normally exceed three feet in diameter, but it has one of the tallest flower spikes.

Again I temporarily add a list of others until I have time to add descriptions:
Agave
Opuntia
Maihuenia
Sempervivum

[Probably more to come]

Exotic-looking flowers

Hedychium coccineum "Tara"
Hedychiums are normally known (in England) as ginger lilies, and they rae related to the edible ginger. This variety of H. coccineum is said to be somewhat hardier than the type, and so to stand a fair chance of surviving an English winter in a warm position if given a thick mulch and good drainage. It can grow to 10 feet high and 3 feet across, with lance shaped pointed leaves up to 20 inches long, though mine has so far remained at about half that size. It is topped by a 10 inch spike of orange flowers in late summer/autumn. I have heard "experts" state that if this plant is not brought under cover for the winter (in England) it will not flower, but this is simply not true. Mine has remained undisturbed in my garden through a number of winters now and has never failed to produce several flower spikes in late summer/early autumn.

Hedychium densiflorum;
This has slightly smaller leaves than the previous species, but grows up to 15 feet tall and 6 feet or more across. The fragrant late summer flowers are orange or yellow, in an 8 inch spike. There are also named varieties with somewhat different shaped flowers.

Hedychium forrestii
The leaves, up to 20 inches long, are narrow, stemless and sharply veined on this species. It can grow up to 5 feet tall and 2 feet across. The spike of white flowers is up to 20 inches long.

For the moment, just a list of others:
Arums
Lilies
Clianthus
Calceolaria
Hemerocallis
Passiflora
Campsis
Lysichiton
Zantedeschia
Ligularia
Cardiocrinum (short description on the page about my own garden)
Crinum
Dracunculus (described on the page about my own garden)
Allium "Globemaster"
Allium giganteum
Hibiscus
Agapanthus
Eremurus

[Probably more to come]

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Links on hardy exotics

Palms, Bamboos, Ferns - an Exotic Garden in England Andrew Withey growing exotic plants in Reading, Berks, England

Huw's Totally Fabulous Palm Page. Huw Collinbourne in North Devon, England, tells how to grow palms from seed, lists "hardy" palms, suppliers, books, gardens in Britain where palms can be seen.

Leonard Holmes' Hardy Palm Information. Based on experience in Virginia. His site describes how to get palms established in marginal areas as well as other cultural matters, and has a useful section on microclimates.

The Hardiest Palm Mark Glicksman gives comprehensive advice on growing Rhapidophyllum hystrix (and a few others), based on experience in Philadelphia, where Trachycarpus fortunei froze to death.

Hardiness in Palms is discussed in depth by The Palm Centre, a nursery in England.

Mike Maxson's Palm Page, covers palms in general, not just hardy varieties - pictures change frequently.

The Cool Tropics. Peter Hueppi has a thorough discussion of hardiness and the growing of palms, cycads, bananas and other "tropical" plants in cold climates, with good cultivation advice, books, links, plant sources and palm germination.

Marc Vissers' Palms Page gives a useful list of sites and books (in English and Dutch) on palms and citrus.

Urban Jungle Nursery site (based near Norwich, UK), in addition to offering specialist plants for sale (bananas, gingers, tree ferns, aroids, cannas, palms, bamboos, etc.) also provides good cultural details for the main groups and provides a page of links to other sites dealing with growing exotics in cool climates.

Lou Smith's Winter Hill Plants is a nursery site specialising in exotic, rare and unusual plants in the UK available via mail order. It gives quite a bit of useful information as well as being a source of hard-to-find seeds and plants.

Other exotic gardening links (a few I haven't yet tried yet):

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Books on hardy exotics

"The Royal Horticultural Society Gardeners' Encyclopedia of Plants & Flowers" is a great reference work to find out what plants look like and what conditions they need to thrive. It does not deal just with hardy exotics, but covers the full range of garden and house plants, and compared with other sources seems somewhat pessimistic about the hardiness of marginal species. It is a big book, giving information about over 8,000 plants, with 4,250 photographs and 640 large pages. Published 1994 by Dorling Kindersley Ltd., London, and by BCA (London, New York, Sydney & Toronto). It does not quote an ISBN number, but gives a reference number CN9651.

"The Royal Horticultural Society A-Z Encyclopedia of Garden Plants" is an even bigger book in the same series. Whereas the foregoing volume is organised in two sections, the larger pictorial one being arranged by size of plant, season of interest and flower colour, this one is purely in alphabetic order of botanical name. The first 54 pages give general discussion of particular groups of plants, particular types of problem and other general aspects of horticulture, but the next 1017 pages cover the specific plants, over 15,000 of them with 6,000 photos. Published 1996 by Dorling Kindersley Ltd., London, and by BCA (London, New York, Sydney & Toronto). It does not quote an ISBN number, but gives a reference number CN3393.

"Exotic Gardening in Cool Climates" by Myles Challis is a much smaller, cheaper book, which I have obtained recently in paperback edition. As the title says, it does deal specifically with this topic. Although some of the many plants listed do not meet my definition of an exotic plant, this is a subjective matter to say the least! It does include tender plants which cannot be left outside during the winter. It also has a chapter on terrarium plants for use in a container in the conservatory. There are chapters on the history of exotic gardening, useful sections on layouts, general soil preparation, maintenance and some beautiful photographs. Then there are the sections on the plants themselves (lots of choice), and the book ends with lists of plants to suit particular conditions. Most of all, it conveys an immense enthusiasm for this type of gardening to inspire anyone reading it. Thoroughly recommended. Published 1993 (paperback 1994) by Fourth Estate Ltd, London. ISBN 1-85702-187-8

"Grow Something Different" by Nick Wray is not confined to exotics, but does include quite a number. Those it does cover it does very well, including comprehensive cultural instructions. It includes some plants omitted by Myles Challis, despite being a smaller book covering a wider range of subjects. Published 1995 by BCA by arrangement with BBC Books. No ISBN number is given, but it quotes a reference number CN1248.

"Foliage Plants for Your Garden" by Douglas Bartrum is by no means confined to exotics, but does cover a wider range of certain groups (especially rheums, gunneras and bamboos) than the other books listed. Unfortunately, I suspect it is long out of print. If you manage to find it, beware of the out of date Latin names for some plants. For example, Hosta sieboldiana is sometimes correctly named, sometimes called Hosta glauca, and in one place described as "Hosta glauca (formerly called Funkia sieboldiana)"! Published 1961 by W & G Foyle Ltd., London.

"Large-Leaved Perennials" by Myles Challis is again not confined to exotic looking plants, but has a large section on them. There is, not surprisingly, some overlap with the other book by the same author listed above, but much of the useful material is only in this one. Published 1992 by Ward Lock Ltd., London as part of a foliage plant series. ISBN 0 7063 7058 9.

"The Good Web Guide - Gardening" by Sue Little is a classified, descriptive list of gardening web sites. Each site is rated for navigation, readability, reliability and speed. Generally one to two web sites per small page, though some are given more space. Published 2000 by The Good Web Guide Ltd. as part of a series of subject-based web guides. ISBN 1-903282-00-4

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Suppliers I have used (successfully):

Architectural Plants, Cooks Farm, Nuthurst, Horsham, West Sussex, RH13 6LH (phone 01403 891772) - Specialise in exotic-looking "architectural" plants such as hardy palms, yuccas, agaves, bamboos, "hardy" bananas, etc. - the sight of their nursery is an inspiration
Burncoose & South Down Nurseries, Gwennap, Redruth, Cornwall, TR16 6BJ (phone 01209 861112) - suppliers of unusual plants
Paradise Centre, Twinstead Road, Lamarsh, Bures, Suffolk, CO8 5EX (phone 01787 269449) - Growers of unusual bulbs/tuberous plants
Broadleigh Gardens, Bishops Hull, Taunton, Somerset, TA4 1AE. (phone 01823 286231) - Specialists in small bulbs

I'm sure there are others just as good.

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