Best shrubs and small trees for container gardening

 

shrubs for container gardening

Acer [Maple; Japan]

The majority of maples are sizeable deciduous trees and of little value where space is at a premium. However, the Japanese maple, A. palmatum ‘Dissectum Atro-purpureum’ (apart from labouring under an uncommonly long name), is slow growing and does not reach more than about 2.4m/8ft in a container after many years. The purple leaves of this tree turn a vivid dark scarlet in the autumn before they fall. There are a num­ber of cultivated garden varieties of A. palma­tum with a wide range of leaf size, shape and colour; they all have dissected leaves, some­times very feathery and some almost fern-like. Japanese maples strongly dislike winds and can suffer damage from them. Their young growth in the spring can occasionally be nip­ped by a late frost. They should, therefore, be placed in situations offering them shelter from both winds and early morning sunshine as the latter when striking slightly frozen new growth can cause burning which would not occur if the frost melted slowly in shade. Propagation is by grafting, a difficult process for the amateur.

Arundinaria [Bamboo; Japan]

Provided that the invasive nature of the evergreen bamboos is appreciated and an attempt is not made to grow them together with other plants, they can be very useful as focal points. Many of the family are quite tall growing and unsuitable for growing in containers – unless they be extremely large.

There are, however, a few which, if grown alone in sizeable tubs, will thrive in either sun or some shade. None of the species like wind and despite the idea that they are often asso­ ciated with water, none of them like their feet wet and do prefer a dry soil. A. variegata (Sasa fortunei), which grows up to 1.2m/4ft, has pale green canes and dark green leaves striped with white. A. viridistriata (Sasa jygrnara), which grows l-2m/3-6ft, has purplish-green canes and dark green leaves with rich yellow heavy stripes. The latter plant can be cut down to the ground each spring to encourage the growth of and display the attractive new foliage. Over­ grown plants may be divided and replanted in spring.

Aucuba japonica variegata [Variegated Laurel or Gold-dust Tree; Japan]

This shrub from Japan was terribly overdone in the Victorian era when it was used in par­lours, greenhouses, shrubberies and practically ) every other situation. It is, however, a very

tough and tolerant small female, evergreen shrub which provides cheer during winter months in window boxes in mild climates. Being able to stand shady conditions, which little else would, a polluted atmosphere and a good deal of neglect, it is a useful plant for really difficult situations.

The aucuba will certainly repay, being given reasonably good conditions, by producing large glossy leaves with spots and splashes of gold and, occasionally, bright red berries in autumn. Only female shrubs of this genus pro­duce berries as they are dioecious (separate sexes). If several shrubs are used there is likely to be a male in the collection – or there could be one in the area which the bees will use. Cuttings, about 20cm/8in long, root quite easily in the spring.

Azalea [Asia]

The botanists have recently moved all the plants that used to be called azaleas to the rhododendron group where they belong botanically, but it is still very convenient to use this category for the fragrant deciduous shrubs like the Ghent hybrids, with long tubu­lar flowers – all of which have some of the characteristics of the yellow parent A. pontica (syn. Rhododendron flavum) and flower in May-June and A. mollis (syn. Rhododendron sineuse) which are not usually scented but flower early in May. Colours range from cream, yellow

and buff to pink, scarlet or orange. These are quite tall growing (up to 1.5m/5ft) but not necessarily quick growing and will in time need some pruning. Faded flowers should be removed before seed pods begin to form. The Kurume hybrids are evergreen, very dwarf growing and smother themselves in flowers during April and May. Most varieties have Japanese names and come in a wide range of colours. All azaleas need an acid soil and some shade, although the evergreens will take sun and need shelter from stormy winds. Propaga­tion is by cuttings or layering.

Berberis [Barberry; Asia/South America]

There are well over 400 different species of berberis known and they have deservedly rocketed into popularity in recent years. Starting with the deciduous kinds, B. thunbergii is fairly compact and comparatively upright. It is usually less than 1.2m/4ft tall, has pale yellow flowers, red berries and colours beautifully in the autumn when the small holly-like leaves turn red. The variety B. thunbergii ‘Atropurpurea’ has foliage which is the colour of copper beech and colours beautifully too. There is also a dwarf form, ‘Nana’, of this.

Charles Darwin discovered B. darwinii in Chile in 1835. It is a spendid evergreen berberis which will eventually reach 1.8m/6ft tall. The flowers are yellowish-orange and are borne in

roses for containers

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heavy clusters during May, almost smothering the small shiny leaves. The berries are dark purple. B. x stenophylla is an evergreen hybrid with delicate arching stems with dark green leaves which are hidden by small golden-coloured flowers at the end of April. It is capable of becoming quite tall but there are several dwarf forms, including ‘Corallina Compacta’ and B. x stenophylla (syn. daminii) ‘Nana’ which rarely grows taller than 46cm/ 18in and bears rich yellow flowers in May. Cuttings 8-10cm/3-4in long taken in August and September should root by the next spring.

Buxus [Box; Europe/West Asia/North Africa]

B. sempervirens is the small-leaved dark glossy evergreen shrub used for edging borders and for clipping into topiary. Small already shaped plants are occasionally available; they are slow growing and much time has been devoted to training them to the particular shape. They end up by being fairly expensive and should be looked after. Small mound shapes are useful in window boxes in mild climates where that shade of dark green is appropriate, and small plants can look very attractive spilling over the edge of mixed plantings. They are reasonably happy in any situation – they just ask to be watered when they need it. In the autumn and in some positions they take on a rusty hue. Propagation is by cuttings in late summer.

Calluna [Ling or Heather; Northwestern Europe/ Eastern United States]

The evergreen Lings, which vary in height from 8cm/3in to 60cm/ 2ft, like a lime-free soil which is not over-rich and a dry open position. They can be grown quite successfully in hanging baskets providing that the soil mix is right and that it is not shaded. Flowers of pink shades and occasion­ally white are produced in the autumn and there are double varieties like ‘Alba Plena’ -double white – and ‘Alportii’ – a tall crimson single and ‘H. E. Beale’ a rose-pink double. Increase by cuttings after flowering.

Camellia [China/Japan/Korea]

For years camellias were regarded as tender when all the time they were quite hardy. Opening buds and flowers are, however, subject to damage by morning sun after night frost, but many problems can be overcome if these plants are situated other than in a position facing east. They are ideal for growing in tubs and large pots. The species C. japonica and the hybrid C. x williamsii are the most commonly seen and new hybrids from each of these two parents are recommended. C. japonica, with characteristically polished leaves, is capable of growing into a large shrub (2-4m/6-12ft). Most of the named hybrids are of medium size but growing them in containers tends to reduce the ultimate size of the plants. The handsome large flowers are usually produced between January and early May and may be a wide range of sizes and forms. There are single, semi-double, double, anemone, paeony and imbricated. Recommended varie­ties include ‘Adolphe Audusson’, large blood-red semi-double, ‘Alba Plena’, large white double, and ‘Pink Perfection’, small shell-pink double. C. x williamsii and its progeny are very free flowering over a period extending from November to May. ‘Donation’, large semi-double orchid-pink, and ‘J. C. Williams’, medium single blush-pink, are two of the best. Camellias are not tender, as said before, but equally they are not plants to be neglected. Keep moist at all times, grow in acid soil, avoid early morning sun when in bud and flower and top dress annually with well-rotted leafmould. Propagation is by cuttings or leaf-bud cuttings in summer.

Cassiope [Northern Hemisphere]

Small evergreen shrub resembling heathers. C. lycopodicides is only 4-8cm/2-3in high with minute dark green leaves. The white bell-shaped flowers appear in April and May. Cassiopes, being native to Arctic regions, need cool growing conditions in a shady north-facing position and a peat-based soil mix. Propagation is by cuttings.

Chaenomeles or Cydoma

Chaenomeles or Cydoma [Japanese Quince; Asia]

The plant C. speciosa, usually called simply japonica, has laboured under several different names for several de­cades. It has at last come to be accepted as C. speciosa. This is one of the few depth-of-winter flowering deciduous shrubs which is not a bit difficult but is particularly beautiful. Given its head it is really quite a large shrub capable of reaching the house guttering, but by careful training and pruning it can be kept within bounds.

It is perfectly hardy and in sheltered positions often begins to flower in December with apple­like saucer-shaped red blossoms about 4cm/ l^in across on the naked branches. These can continue for several weeks. Named varieties include hybrids such as ‘Apple Blossom’, white, pink-flushed flowers; ‘Crimson and Gold’, red and yellow; ‘Rowallane’, deep red; and ‘Nivalis’, large pure white.

C. japonica [Maules Quince; Asia]

This deciduous shrub is much smaller growing-up to 90cm/3ft-but inclined to sprawl. The flowers, bright orange flame in colour, are freely produced but do not appear until April or May. Out­standing hybrids are ‘Knap Hill Scarlet’,

orange scarlet, and ‘Pink Lady’, clear rose-pink. These are the flowering quinces which produce odd-shaped fruit that can be made into pre­serves. They all like sun and a good rich potting soil. If possible, buy plants which have been pot-grown as they take a little time to settle down again after being lifted from the open ground. Seeds will germinate freely, but named varieties must be increased from cuttings.

Cistus [Rock Rose or Sun Rose; Mediterranean]

Cistus are evergreen shrubs, rather on the borderline of hardiness, but cuttings root easily and some small reserve plants should ideally be taken which will survive even in the worst winter in a cold frame. More than the cold they dislike the wet – or really a combination of the two. C. x corbariensis is a bushy shrub 45-90cm/ l^-3ft in height having 4cm/l^in single rose­like flowers of white with a yellow base. Less hardy but with one of the best flowers – purple-red with a dark blotch on each petal – is C. x purpureus which grows to about 90cm/3ft. C. ‘Silver Pink’ is an exceptionally pretty almost hardy hybrid. A number of named hybrids are offered by some nurserymen in mild climates. A light sandy soil suits them best and they love the sun, sheltered from winds.

Clematis [Asia/North America]

Clematis are some of the most beautiful climbing plants obtainable. They provide height and with their large and vivid flowers add splashes of colour over a long period. Given long canes or a background framework they will attach themselves and require no tying to their supports. Good sized tubs are best, affording an extensive and cool root run. Some shade for the roots must be given and this is best done either by planting some dense but shallow-rooting plants in the tub or by placing tiles (or a collection of attrac­tive pebbles from the beach) over their feet. The top growth, however, loves the sun. The most suitable for containers are those deciduous types which flower on the extremities of new growth as this allows their being pruned al­most to the ground each year. With young plants this pruning is best done in February but more mature specimens can be doctored in December. C.jackmanii (deep-purple) and the many other named sorts offer a very wide choice of colour, from May to September. Without doubt the best way to choose the colour and form of flower that appeals most is, in the months of July to September, to visit a garden with a good collection of clematis. Propagate by stem cuttings in July.

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