Subtropical gardens
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Feasting on mangoes under swaying palm trees with the scent of frangipani on the breeze may conjure up images of the tropics but even gardeners not blessed with a naturally tropical or subtropical climate can, with a little attention to providing sheltered pockets and overhead protection, grow many plants that might seem hard to imagine thriving in temperate gardens. Provided your frosts are not too hard, too prolonged or too often repeated you will be able to find isolated microclimates where tender
subtropicals thrive.
Many spectacular plants from Asia, South and Central America, southern Africa and Australia will withstand reasonably long periods of cold weather but they will not withstand freezing. Making the most of subtropical plants requires that you have a good understanding of their climatic requirements and the way the weather affects your garden.
Any garden will contain a variety of microclimates that can display widely varying characteristics. Some small pockets may be frost-free, others will be exposed to almost continual breezes and some areas may hardly ever see any rain. Gardeners in mild frost-free areas can devote their entire gardens to subtropicals if they wish, but for most of us, growing subtropicals means utilising our gardens’ microclimates to their greatest advantage.
Protection
Strong cold winds can be just as damaging as frosts and continual cool sea breezes, in particular, can stunt the growth of subtropicals. Providing adequate wind shelter is vitally important in the subtropical garden, but take care that in so doing you are not reducing the air movement to the extent that frost pockets are created.
Hedges, pergolas, shadehouses, overhanging eaves and even carports will create small sheltered areas where subtropical plants can be grown. Tender climbers, such as Bougainvillea and Passiflora, may be grown up against the house walls under the protection of the eaves. Many orchids, especially cymbidiums, will thrive with just the minimal protection offered by a shadehouse.
Container-grown plants can be moved around with the seasons and may be used to create a subtropical effect even in cool areas. Container growing is also useful with subtropicals that will grow in the garden but not flower. Gardenias, for example, will withstand moderate frosts, but because they need prolonged warm weather to bloom they may not flower reliably unless kept in a greenhouse or a sheltered spot until well into spring.
Fruit
Citrus fruit is probably the most widely grown subtropical plant. The hardiest common citrus is the ‘Meyer’ lemon, a lemon/orange cross that can withstand around -5°C, while the most tender is probably the Tahitian lime, which tolerates only very light frosts, if any. Most citrus will withstand occasional freezing but the fruit becomes thick-skinned and dry with prolonged cold.
Citrus plants are very ornamental as well as functional. Their combination of lush glossy foliage, masses of fragrant waxy, white flowers and spectacular fruit would make them first rate garden plants even if they were inedible. They range in size from small shrubs to large trees. In mild areas, citrus will thrive without protection and can even be used for hedging.
Other subtropical fruitsi, such as tamarillos, babacos, cherimoya, guavas, avocados grow extremely well in the mild gardens and if you have the choice opt for highland clones that are often a little hardier.
Ornamentals
There is an enormous range of shrubs and trees that are generally considered just a little tender for temperate gardens. But with careful siting and a caring gardener, many of them can be grown to perfection, especially in the far north.
Spectacular flowering trees, such as Brachychiton acerifolia and Stenocarpus sinuata, are large enough that they are difficult to protect, so a mild climate is essential. In cooler areas, however, many small trees, such as Cassia fistula, can be protected by larger trees and will often thrive in sheltered pockets. Hardier subtropical trees, such as jacaranda and Grevillea robusta, are tender when young but become considerably
tougher as they mature.
Nothing conjures up thought of the tropics quicker than palms and many palms are truly tropical plants that struggle to grow in temperate climate gardens. However, there is also a wide range of reasonably hardy palms. Among the best known are the Canary Island Date Palm (Phoenix canariensis), the Chinese Fan palm (Trachycarpus fortunei), the European Fan Palm (Chamerops humilis), the Blue or Hesper Palm (Butia capitata) and the Nikau (Rhopalostylis baueri). Consider also the beautiful blue palms, Brahea armata and Brahea edulis; the Chilean Wine Palm (Jubaea chilensis); Archontophoenix cunninghamiana; the Washingtonia, Sabal and Livistona fan palms; the Kentias (Howea species) and the Lady Palm (Rhapis excelsa). Palms generally prefer shade when young, so they can be grown under a protective tree canopy, and they are usually very good container plants.
The range of subtropical shrubs is truly enormous and is really only limited by your willingness to experiment. Often the greatest problem is obtaining the plants in the first place. Some mainstream nurseries stock a good range of subtropicals but you will often have to buy by mail order and may even have to raise plants from seed. Start with the reasonably tough plants like Gardenia, Tibouchina, Bouvardia and Hibiscus and if they seem to do well, you may like to try something less forgiving, such as Dichorisandra thyrsiflora, Iochroma cyaneum or Ruellia macrantha.
Large succulents can look spectacular in subtropical gardens. They create stark silhouettes and very strong lines that contrast well with soft arching palm fronds. Many of them have impressively large and colourful flowers. If you have the room try the tree-sized Aloe bainseii; the archetypal western movie cactus, Carnegia gigantea; or the very unusual large-leafed Cyphostemma juttae. Those with smaller gardens would be better with some of the succulent euphorbias, the smaller aloes and epiphytic cacti.
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Much of the subtropical look comes from creating strong contrasts. Vividly coloured large flowering shrubs growing beside large cacti under tall, narrow palm trees create a scene that is immediately different from the muted tones that are more common in temperate gardens. But spectacular as this may be there is always the risk of creating something of a ‘Hawaiian shirt’ garden. Generally, you can get away with extremely gaudy combinations in the subtropical garden, but you may find the result is a little hard to live with. Subtropical gardeners, more than most others, need to think carefully about how they use colour, varying growth forms and foliage types.
Copyright Geoff Bryant
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