Читать книгу Architectural Plants - Christine Shaw - Страница 13
ОглавлениеPalm trees are the ultimate architectural plant: they are shapely, evergreen, and add an exotic touch to any garden. Although they are associated with steamy jungles or baking hot deserts, many are hardy enough for average gardens in much cooler climates.
The palms that are featured on the following pages have all been selected for their hardiness and availability, as well as for their good looks and ease of cultivation.
Choosing the correct palms for your particular garden is important. If very cold temperatures down to -20°C (-4°F) are regularly experienced, then Trachycarpus fortunei would be the palm to choose if it is to stay unprotected for the entire winter. Looking out into the garden during a cold snowy winter and seeing a perfectly happy palm tree is a sight that always lifts the spirits.
Palms are always best planted directly into the ground, rather than grown in containers. In the ground they can grow unchecked to their full stature. The foliage of palm trees planted in the garden always looks greener and healthier than the foliage of those kept in tubs. But if planting in pots is your only option – to stand on the paving around a swimming pool or for a roof terrace, for example – then choose the largest pot possible. Palms kept in small pots not only suffer from having their roots cramped, but the ends of each leaf tip are also much more likely to go brown due to lack of food and uneven amounts of watering. Plants in pots are totally dependent on us for food and water, whereas plants in the ground can usually find their own sources of nourishment and moisture once they are established.
As long as it is given an adequate supply of water and protection from the wind, a healthy palm should live for many decades.
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Chamaerops humilis is a slow-growing dwarf palm, perfect for small gardens.
Although palms are reasonably easy to propagate from seed, this method is not for the impatient gardener. Years can be spent waiting for specimens to mature enough to make a real difference to the view from the house windows. Buying a good-sized palm that is at least eight years old ensures instant appeal and larger palms are also much hardier than small seedlings.
Chamaerops humilis and Trachycarpus fortunei can grow in either sun or shade, but all of the other palms featured in this chapter need some sunshine to look their best. All palms need adequate moisture but they hate to have their roots permanently soggy.
Whether you are planting in the ground or in pots, check that the soil contains enough grit, flint, rock or gravel to make sure that excess water can drain away. Virtually all palms, with the exception of Chamaerops humilis and Phoenix canariensis, need to be sited in a sheltered position away from coastal gales and exposed hilltops. Strong winds can leave the leaves looking battered and messy. Large palm foliage, whether fan-shaped or feathered, looks so much better if it is straight and undamaged.
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Phoenix canariensis is a large, stately palm that is suitable for mild gardens only.
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Washingtonia filifera adds a glamorous look to any conservatory.
Palms appreciate a good feed in late spring, when they are actively growing. Sprinkling a few handfuls of a blood, fish and bone mixture on the surface of the soil around each trunk is usually sufficient. Palms rarely need any means of staking and support; each trunk is usually sturdy enough to take care of itself.
When the lower leaves become brown and scruffy, usually because of age, some maintenance is required. The leaf tips are the first part to look untidy, but this can be remedied by lightly trimming them off with a sharp pair of scissors or secateurs (see photograph, top right). This process can be repeated several times as the leaf ages, until so much of the leaf has been removed that more drastic surgery becomes necessary. Once this stage has been reached, the removal of the entire leaf right down to its base becomes desirable. Using a very sharp pair of secateurs, or a saw if the leaf base is especially thick, cut as close to the trunk of the tree as possible, leaving a nice tidy cut. This cut piece will be visible for years, so care should be taken to make it as pleasing to the eye as possible. As the palm matures, and more leaves are removed, these cut leaf bases become numerous along the entire length of the trunk. If the cuts are all made carefully and to the same size, a pattern starts to form, which gives each palm a cared-for appearance (see photograph, below right).
If you have plenty of space in the garden and a reasonably generous budget, instead of just planting individual specimens, go for a more natural look. Palms look so much nicer planted in groves of all the same type but of many different sizes. With a bit of imagination, palms grouped together in various stages of maturity can give the impression of having been there for years, with the smaller trees the result of seedlings produced by larger ones.
Although large palms aren’t the cheapest plants around, if they are looked after properly, it will be money well spent, as healthy palms can live for many decades. Palms should always remain a focal point of the garden, adding more of an exotic presence with each extra year’s growth.
Palms are low-maintenance plants that suffer very little from pests and diseases. If grown under glass in a greenhouse or conservatory, red spider mites can be a problem. Outside, if the climate is too cold and wet for the chosen type of palm, then leaf spot can become unsightly and spread throughout the entire plant if left unchecked.
If a very cold winter is forecast and the hardiness of palms selected for planting outside is in doubt, emergency tactics can be applied. Gather all the palm leaves together vertically and tie them up fairly tightly with string. Then wrap hessian, horticultural fleece or any suitable porous material many times around the whole lot and fasten it securely (see page 155). This should protect the most vulnerable parts of the plant – the innermost younger leaf shoots – until the worst of the cold spell is over. Do not use bubble-wrap or polythene, as this could trap excess moisture and lead to rotting.
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Manicuring palm leaves using a pair of secateurs removes any brown leaf tips that can look unsightly.
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Butia capitata has had many old leaves removed over several decades, leaving a tidy arrangement of leaf bases.
Brahea armata
Blue Hesper Palm
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The unusual colouring of Brahea armata makes this palm a desirable acquisition.
SYN. Brahea glauca
Erythea armata
A beautiful silvery blue desert palm, native to southern California and Mexico, and named in honour of Tycho Brahe, a Danish astronomer. It is one of the prettiest palms that can be grown in colder climates, and is often in short supply due to popular demand.
As well as being one of the most desirable palms, it is also one of the slowest-growing: it can take 15 years to reach 1.8m (6ft) and is therefore usually one of the most expensive to acquire. Buying a decent-sized specimen is essential unless you have great patience and youth on your side.
In its native environment, Brahea armata can cope with temperatures as low as -10°C (14°F), but the desert conditions mean that it is used to dry, crisp air with just short spells of really cold weather. If it is grown outside in places that experience high rainfall, foggy conditions and prolonged periods of cold during the winter months, then it becomes much trickier getting it to survive.
Unless warm, dryish winters can be guaranteed, the best way of cultivating Brahea armata is to grow it in a large container. It can then be put outside during the summer and overwintered under glass. Make sure the compost has masses of grit stirred into it to make the drainage exceptionally good. Soil-based compost is preferable to peat. Water the pot well during late spring and summer, and keep fairly dry in late autumn and winter. It is important to feed any palm, especially if it is grown permanently in a container. A couple of handfuls of blood, fish and bone applied in late spring will keep it looking healthy. If Brahea armata is grown outside all year round, choose a warm, sunny spot in a sheltered position.
Although some huge 12m (40ft) tall specimens can be seen in the wild, Brahea armata palms in general cultivation are unlikely to exceed 3m (10ft).
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A close-up of the blue, fan-shaped leaves.
Butia capitata
Jelly Palm
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Butia capitata has elegant, arching blue-grey fronds, and is a good choice for mild gardens.
SYN. Cocos australis
Cocos capitata
Cocos corinata
Butia capitata is an impressively sturdy palm, with large, blue-grey leaves that take the form of arching, feathery fronds. Plants that are raised from seed have a wide colour variation, ranging from greenish-grey through to a pale silvery blue.
Away from its native habitats of Brazil and Argentina, it is maddeningly slow-growing if planted outside. Regardless of its size when purchased and how long it is nurtured and loved for, the wretched thing seems to stay exactly the same size. Each year new fronds are formed with the promise of adding a little extra height but, as they unfurl and arch gracefully downwards, no visible increase in stature is ever observed.
With this in mind, buying a good-sized specimen is essential. In temperate climates, plants over 4m (13ft) are rarely seen. Although not very hardy, Butia capitata is such a splendid palm that it is well worth considering even for a cold garden. Planted out in a sunny, sheltered spot, it can be cosseted during the winter by pulling all the leaves up vertically and tying them together, then surrounding the whole plant with layers of horticultural fleece (see page 155). This will keep it cosy until warmer weather returns.
Alternatively, plant it in a container – the larger the better – and wheel it inside under glass when the temperature drops. Mature plants can be rather weighty, so the purchase of a purpose-built, plant-moving sack barrow would make this job less of a chore. Stand containers in the lightest, sunniest part of the conservatory or greenhouse, where the palms will be quite happy for several months. As soon as the very worst of the winter weather is over, move them back outside. If left for too long inside, they can become susceptible to attacks from red spider mites and scale insects.
Chamaerops humilis
Dwarf Fan Palm
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The leaf stems of Chamaerops humilis are covered with sharp barbs along their entire length.
Instead of the usual palm tree shape of a mass of leaves on top of a single trunk, Chamaerops humilis is a low-growing, bushy palm with numerous stems coming from the same root system to create its own natural grove. The foliage is made up of copious, stiff fans that form a dense clump. Each leaf petiole (stem) is covered with sharp barbs along the entire length. The leaf colour ranges from green, silvery green to almost blue. The bluest plants are sometimes given a separate identity, namely Chamaerops cerifera.
Chamaerops humilis is the only Mediterranean palm that really thrives in colder climates. Its natural habitats include Spain, Morocco and Sicily. A tough, hardy palm, it can be grown in a variety of conditions. Because of its density, it is able to shrug off strong winds and salty gales without developing a battered and shredded appearance, as happens with many palms grown in exposed positions. This makes it a perfect choice for any coastal garden.
It is extremely slow-growing – a twenty-year-old specimen is unlikely to be more than 1.2m (4ft) tall and 1.2m (4ft) across-which makes it suitable for containers. Chamaerops humilis is unfussy about light levels. A sunny planting position would produce the fastest growth, and older plants would eventually produce little yellow flowers, followed by fat bunches of large, glossy, orange berries. Light shade is also perfectly acceptable, where the leaves take on a deeper, prettier green hue. Chamaerops humilis can even cope with conditions indoors, where light levels are quite poor. However, without a few months outside during the summer, new growth would be minimal.
Mature plants start to form little trunks that are usually hidden among the foliage. These are often rather attractive and can be made visible by trimming away some of the external, lower leaves. If one of the central trunks happens to be very straight, then all the outside stems can be sliced off with a saw or sharp knife, to leave just one central, more traditional-looking, single-stemmed palm tree. Any side stems with a piece of root attached can be used for propagation.
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After years of careful pruning, a handsome single-stemmed version can often be achieved.
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The exceptionally slow growth of Chamaerops humilis makes it ideal for a large container.
This method of propagation produces decentsized plants far more quickly than the usual seed-grown method.
Chamaerops humilis grown outside in very cold and wet conditions can sometimes develop chocolate-brown spots on the leaves. These can spread throughout the entire plant if the disease is not dealt with quickly by removing affected leaves and drenching the whole plant with a systemic fungicide.
Cycas revoluta
Sago Palm
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Cycas revoluta is slow-growing enough to stay in a large container for many years.
Cycas revoluta is difficult to categorize. Its appearance is somewhere between a palm and a tree fern, although it is actually neither. As it tends to resemble the former slightly more, it fits rather well into this chapter.
This primitive plant has been around for several hundred million years. Its natural habitat is nowadays restricted to China and parts of the East Indies. Cycas revoluta is one of the world’s slowest-growing plants, taking about fifty years to reach 1.5m (5ft) tall. Because of this, it is a good contender for growing in a terracotta pot in the conservatory.
Its base is similar to that of a coconut, and from this will emerge palm-like fronds covered in a waxy coating, giving it an almost artificial look. The number of new leaves sent out each year could be anything from nil to thirty, depending on its mood, but the year’s growth is produced within a few weeks, rather than gradually throughout a whole season.
Crowing Cycas revoluta is a bit of a challenge. It is almost best neglected, as it is tempting to fuss over such a special plant and give it far more attention than it requires. It is very easy to overwater, and the leaves will show their displeasure quite quickly by turning yellow. If this happens, there is little to be done except to cut them off and learn from the experience. Hopefully, the following year new, fresh green ones will sprout once more from the base.
Cycas revoluta can be grown outside only in very mild areas that rarely get any frost. If your garden is so favoured, plant in a sunny, well-drained spot. In colder climates, keep it in a shady part of the conservatory where direct sunlight through the glass cannot scorch it. Water sparingly until new fronds start to emerge, then water regularly until growth stops. Apart from a light dose of nitrogen in late spring, the only care needed is an occasional wipe over with a cloth to keep the leaves free from dust, and periodic inspections for scale insects.
An important point worth noting is that plants must never be moved when new fronds are unfurling because this upsets their growing pattern as they try to follow the sun’s direction. Instead of being symmetrical and curved, the leaves can end up crooked and twisted.
Jubaea chilensis
Chilean Wine Palm
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Jubaea chilensis is a massive palm with a regal presence.
A huge, vast tree that has the thickest trunk of any palm. The wondrous sight of a mature plant can bring a tear to the eye – in the world of palms, its majesty is unrivalled.
The trunk, which can grow up to 1.5m (5ft) in diameter, is pale grey in colour with a rumpled appearance, making it look a bit like the leg of an enormous elephant. Large, waxy fronds of foliage arch out from the top of the trunk.
This tree is painfully slow-growing, and buying anything less than 1.8m (6ft) tall to start with requires patience and perseverance. In its native Chile, it can reach 18m (60ft), but in cooler climates it is unlikely to exceed 9m (30ft), even after a hundred years.
Jubaea chilensis used to be a familiar sight all over Chile but now, alas, it is a rare and protected species. Its exploitation for the production of palm wine – the trunk of a mature plant contains about 450 litres (100 gallons) of the sugary sap that is the main ingredient of this alcoholic beverage – has led to its sad decline. Unfortunately, the harvesting of this sap results in the death of the tree.
Propagation is from the palm’s miniature edible coconuts. Seedlings and young plants are very tender, but they become surprisingly hardy as they mature.
Giving this palm perfect growing conditions will help to speed up its growth a little. Rich, moist, fertile soil always gives the best results. It also grows faster in a warm, sun-baked spot, although being in a lightly shaded position will do no harm. The surrounding soil should be kept moist for the first couple of years after planting. The roots can then usually find their own water supply once established. Younger plants could spend the first few years of their life in a container but they should never be allowed to dry out.
Phoenix canariensis
Canary Island Date Palm
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The large, elegant fronds of Phoenix canariensis add a touch of the tropics to any garden.
This beautiful, shapely palm is extremely popular with enthusiasts of architectural plants – it seems to sum up everything that is exotic in the gardening world. Massive, arching fronds explode out of what looks like a huge, thick pineapple. The foliage appears lush and soft as it swishes around in the wind, conjuring up images of windswept desert islands and Robinson Crusoe. It is one of the most frequently planted palms in the world, and is seen by numerous holidaymakers on their travels, who then wish to have their own specimen as a souvenir of a sunny vacation.
What a pity, then, that its hardiness is not that good. In temperate climates, this palm is reliably hardy only in warm inner cities and mild coastal regions. But, because it is so beautiful, many gardeners are prepared to take a risk and plant it anyway. If this is the case, purchase a plant as large as possible – the bigger the palm, the hardier it is – and find the sunniest spot in the garden.
For a palm, Phoenix canariensis is fairly quick-growing, so keeping it in a pot is a difficult task. If the winter is fairly dry, it can endure quite low temperatures. If it is a wet winter, this can lead to trouble, as the vulnerable part of the central growth point can rot and never recover. Wrapping the plant up for the winter can help: tie all the foliage together vertically and cover it with something warm but porous, such as hessian (see page 155). With all the leaves huddled together, the tougher outer ones shelter the more delicate inner ones.
When brown-bitting becomes necessary (the removal of the lower leaves that have become tatty with age), you will need a large saw. Every time a leaf is removed, saw it off at exactly the same distance away from the trunk and at exactly the same angle as all the others. This leads to quite a pleasing decorative effect around the trunk as it ages. Take care when getting too close to the ends of the fronds: they look soft and harmless but can give a surprisingly painful jab.
Older plants in colder climates can form trunks 4.5m (15ft) tall in around twenty years. Mature plants also form massive clusters of beautiful lush orange fruits. These are inedible, so leave them on the tree.
Trachycarpus fortunei
Chusan Palm
SYN. Chamaerops excelsa
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Trachycarpus fortunei is the hardiest palm in the world.
An essential palm for all exotic gardens. This is by far the best palm for temperate gardens because it is the hardiest palm in the world. It is also one of the easiest to cultivate, coping with a wide range of conditions. It is usually on a single trunk, but multi-stemmed plants are sometimes seen. The entire trunk is covered with coarse, shaggy hair, making it instantly recognizable. The leaves are large and fan-shaped. Named in honour of Robert Fortune, the plant explorer, Trachycarpus fortunei is native to central China.
Although happiest in a sunny spot, this palm can be grown in light levels almost down to full shade, where it remains quite healthy, even if it grows more slowly than it would in a brighter position. Any well-drained soil will do, whether it is clay, loam, peat or chalk, but rich, fertile conditions will always give the best results. It is a greedy plant, and poor soils would benefit from regular applications of well-rotted manure in the spring and early summer.
Avoid planting where the ground can become waterlogged, as this would be detrimental to the roots. Also avoid planting in a position where it is constantly windy, such as on the seafront or the top of a hill. Although this won’t cause any harm, it will give a battered appearance to the leaves, as they easily bend and shred if exposed to strong breezes, and the whole plant can end up looking miserable.
Considering that it’s a palm, Trachycarpus fortunei can tolerate ridiculously low temperatures. As long as it is at least 1.2m (4ft) tall, it can cope with winters down to -20°C (-4°F), which is astonishing for such a tropical-looking tree.
Older plants can produce attractive flowers early in the season. They start off as lumps of yellow close to the trunk and emerge as large arching shapes, which have been wittily referred to as smoked haddocks. The flowers are small but numerous, and gradually ripen to blue-black berries. The whole flowering cycle is interesting to watch, but while this process is happening, the tree is having its energy drained. Ideally, a hardhearted approach should be adopted and the flower buds chopped off at the first sign, so that all available energy can be devoted to leaf production instead.
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Large, luscious fan-shaped leaves emerge from the top of a hairy trunk.
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A healthy plant could produce ten new leaves each year.
Very little maintenance is needed, apart from removing any older leaves as they turn brown. But for those who like a challenge, there is an interesting technique that can be used on the trunk. Popular though Trachycarpus fortunei is, few people would claim that it is beautiful. Its large, hairy trunk. just isn’t that pretty. However, by removing all the hair and exposing the lower waxy layers, you can transform it into a much more tropical-looking addition to the garden. Removing the hair is in no way detrimental to the palm and doesn’t appear to lessen its hardiness. A plant stripped in this way nearly eight years ago and growing in a frost pocket remains perfectly happy.
The instructions given opposite for this technique are for right-handed gardeners.
1. Starting at the base of the trunk, tear away at the hairy fibre at ground level until you uncover the first leaf base.
2. Hold the leaf base in your left hand and slice the right-hand side of it downwards using a very sharp, good-quality, serrated bread knife. Slice around the entire trunk clockwise while peeling away the fibrous surface.
3. You can now see the very first orangey-cream layer.
4. This photograph shows the trunk after three leaf bases have been cut away.
5. Repeat the process, working your way up the trunk.
6. This photograph is a close-up of the trunk with more of the leaf bases removed.
7. Keep working your way up the trunk. This photograph shows the finished result after an hour’s work.
8. Just one trunk will yield a barrowful of fibre. There must be lots of uses for this material but, so far, I’ve failed to discover any!
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The leaves of Trachycarpus wagnerianus are much stiffer and much more beautiful than those of Trachycarpus fortunei.
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Trachycarpus ‘Breppo’ is a smarter, tidier form of Trachycarpus fortunei, and it also has a much fatter trunk.
There are a couple of interesting forms of Trachycarpus fortunei that are well worth mentioning. The first is Trachycarpus wagnerianus, which was once thought to be an entirely separate species.
The leaves of this palm are smaller than those of Trachycarpus fortunei, but straighter and stiffer, giving the tree a much tidier appearance. It can cope with windy positions slightly better, too, without tearing quite as much. It is slower-growing and can be fairly difficult to track down, which makes it more expensive to buy. If seeds are taken from one of these plants and germinated successfully, usually around 25 per cent will come true to form. The other 75 per cent look exactly the same as Trachycarpus fortunei, giving weight to the argument that it is not a separate species.
Another form worthy of special mention is Trachycarpus ‘Breppo’. It’s not often seen, but worth hunting around for. The leaves are large, beautiful and fairly stiff, but it’s the trunk that gives it a superior look. It is stockier than that of Trachycarpus fortunei, and the trunk hair is made up of much longer and fluffier tresses. Removing this would be a pity.
Washingtonia filifera
Cotton Palm
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The white threads of ‘cotton’ contrast well with the thick, sturdy trunk.
A splendid palm tree with huge fan-shaped leaves of vivid green. The fingers of each part of the leaf are tipped with white threads of ‘cotton’, which hang down from every frond, giving a graceful feel to the whole plant.
Named in honour of George Washington, Washingtonia filifera is native to California and all south-western parts of the USA. It is used heavily for municipal planting and is easily recognizable by the thatch of old leaves that hangs down vertically to cover the whole trunk. However, these old brown leaves are considered a fire hazard in some areas, and their removal by brown-bitting is becoming more commonplace. Seeing the clean stout trunks with a head of lush green foliage is a huge improvement on their appearance.
As it is a desert palm, Washingtonia filifera can cope very well with hot, dry atmospheres, making it an excellent choice for an atrium or a large conservatory. Its speed of growth and eventual size of at least 9m (30ft) even away from the desert mean that planting in the ground is by far the best option. When planning their conservatories, some gardeners leave planting spaces in the ground for such plants. If it really has to be grown in a pot, make sure it is a massive one. This palm takes around fifteen years to attain a height of 3.7m (12ft) but then it can speed up and become unmanageable very quickly. Large palms are far too heavy to keep repotting easily. However, this palm is so beautiful, it is tempting to buy one, grow it for ten years and then worry about what to do with it when the time comes.
Growing young plants from seed is very easy and quick. Observing the root system on even newly germinated seedlings will tell you that this palm is used to finding its own water supply: the tap root is about five times longer than the leaf section. But this drought-resistant quality applies only to plants growing in the ground – container-grown specimens must be watered regularly during the growing season.
Full sun is an essential requirement, too. The only maintenance needed is frequent inspections for red spider mites.
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Delicate ‘cotton’ filaments cover the edges of every leaf.
