Garden Conifers

Evergreen conifers are collectively one of the most important groups of trees and shrubs for garden planting. They depend for their impact chiefly on their foliage and overall shape, and because these vary little from one season to the next, the plants help to form the permanent framework of many garden designs. They are especially valuable in winter when they are the main source of massed colour. Evergreen conifers are also extremely useful in their capacity to form a dense screen – not only to hide eyesores, but to create the illusion that a garden is bigger than it really is by disguising the boundary in such a way that the plot appears to continue beyond it. Among their ranks, can be found trees varying in shape from neat, straight pillars to spreading bushes and in size from forest giants to completely prostrate forms. Only the slower-growing or smaller kinds are suitable for putting into an average-sized plot, but even they offer immense scope. As with the broad-leaved trees in the previous chapter, all sizes mentioned are what might be expected after 15 years of growth.

Selection

garden conifersPerhaps the most commonly seen conifer is Lawson’s cypress (Chamaecyparis lawsoniana), which is often referred to as ‘cupressus’. Left untrained it develops into a tall, cone-shaped tree some 4.5 m (15 ft) or more high, clothed with rather drooping, fanlike foliage. It has given rise to a large number of cultivars that are mostly a little less vigorous of growth and are much more interesting garden trees in colours of rich green, gold, silver, and blue. ‘Kilmacurragh’ for instance, is bright green, slender, and upright – rather like an Italian cypress in shape – while ‘Pottenii’ is a pale shade of apple green; ‘Green Pillar’ lives up to its name and, although it has upward-growing branches, it does not seem to suffer damage as easily as do some trees of this shape when weighed down with snow. Another upright-growing cultivar, ‘Columnaris’, makes a narrow silvery blue-green pyramid, while ‘Ellwoodii’, rather less vigorous than the others mentioned, develops into a compact pyramid of feathery grey-blue. One of the bluest of all is ‘Pembury Blue’, a striking conical tree with sprays of light silvery-blue foliage. Of those cultivars with yellow foliage, which bring the warmth of sunshine to a garden even on dull days, ‘Winston Churchill’ is richly coloured and carries its golden foliage in winter and summer alike. A little more vigorous, ‘Stewartii’ is not quite so brilliant, the yellow shading to green at the bases of its branches. Apart from these trees, C. lawsoniana also provides a number of attractive dwarf forms. ‘Minima Aurea’ is a very slow-growing, rounded bush that holds its yellow foliage fans on edge instead of horizontally as most of the other forms do. For a light touch ‘Pygmaea Argentea’ (’Backhouse Silver’) is similar in shape, but has white tips to its dark-green leaves. But the neatest sphere of all is formed by the blue-green ‘Gimbornii’. These three dwarf forms are all slow growing and even ‘Gimbornii’, which is probably the most vigorous, is unlikely to grow to much more than 600 mm (2 ft) across in ten seasons. Where a small conical tree is wanted, ‘Ell-wood’s Pillar’ might fit the bill; this is a scaled-down version of CI. ‘Ellwoodii’ and is unlikely to exceed 1m (3-1/4ft) in height after a decade.

The various forms of the Sawara cypress (C. pisifera) are very different from other conifers in that they have thread-like branchlets. This feature is most striking in the yellow forms, such as ‘Filifera Aurea’ and ‘Gold Spangle’, which eventually make mounds of golden filigree. Both of these are slow growing, but whereas ‘Filifera Aurea’ is unlikely to make a bush greater than 1m (3V4ft) in height, ‘Gold Spangle’ can eventually become much larger.

Junipers also provide an extremely wide selection of shapes and colours to tempt a gardener. A perfect gem for a rock garden is to be found in Juniperus communis ‘Compressa’, which slowly grows into a tiny, compact, green column 450 mm (18 in) high. Of the same shape, but on a much larger scale, is the Irish juniper (J. c. ‘Hibernica’), which climbs to about 2.7 m (9 ft) in height after many years, keeping its slim outline quite naturally. J. c. ‘Depressa Aurea’, on the other hand, is a dwarf, spreading plant. Its feathery-looking, yellow spring growth deepens to gold in the summer and turns to bronze as the days become colder.

J. horizontalis is a creeping juniper and provides a number of colourful cultivars. One of the most brilliant is ‘Blue Moon’, its feathery-looking foliage being bright silver-blue in summer, changing to a greyish tone in winter. Quite vigorous, it can spread over 1.5 m (5 ft) across in 10 years or so. A little more vigorous is ‘Emerald Spreader’, a completely prostrate form with bright emerald-green foliage.

Under J. x media (syn. J. chinensis) are listed a number of natural hybrids. ‘Blaauw’, at 1.2 m (4 ft), is unusual in that it has upright feathery branches that splay out a little from the centre, eventually to form a distinct vase shape. Its foliage colour, a good blue-green, is retained throughout the year. ‘Pfitzeriana Aurea’ is a low bush with all-but-horizontal branches spreading one over another. The new growth is yellow in summer but tones down to greenish yellow for the winter. It has given rise to a natural mutation called ‘Old Gold’, with only about one third of the growth rate of its parent, but of a deeper golden colour which does not green up in the winter months.

Silvery blue is the colour of the Nepal juniper (J. squamata ‘Blue Star’), which eventually forms a compact hummock of branches that are given a rather spiky appearance by the bright leaves. It is hardly likely to outgrow its allotted space since it may take 10 years to reach a spread of 300 mm (1 ft) or a height of 250 mm (10 in). But although it is diminutive in size, its colour ensures it never goes unnoticed.

Mention of spruce (Picea) may make you think of Christmas trees, but the genus has many garden-worthy forms in its ranks. The Christmas tree, or Norway spruce (P. abies, syn. P. excelsa), has provided a number of cultivars, all slow-growing, that make neat, rounded little bushes, suitable for even the tiniest of plots. Good examples are P. abies ‘Little Gem’, a bright-green, mop-like bush only 300 mm (1 ft) high and a little wider, and the dark-green P. a. ‘Nidiformis’, or birds-nest spruce (so called because of the central depression that forms in the top of the young bush), which grows to perhaps half as big again.

Eye-catching is certainly the right term for the Caucasian spruce (P. orientalis ‘Aurea’). This one has a similar appearance to the ordinary Christmas tree spruce, but puts on a startling display in spring when the very pale yellow new growth shows up against the dark green of the rest of the foliage. These new shoots gradually turn gold, then green, although the tree never completely loses a hint of sunniness. This is not a tree for a very small plot unless you are prepared to replace it after about 10 years, when its height will be 3 m (10 ft) or so.

Making a strong claim as possessing the most brilliant blue of all conifers are the forms of the Colorado spruce (P. pungens). The cultivar ‘Globosa’ makes a dense, flat-topped little bush about 600 m (2 ft) high and wide with silver-blue needles. ‘Koster’ slowly develops into a slender, conical tree some 3 m (10 ft) high that holds its intense silver-blue colour throughout the year.

No look at garden conifers would be complete without a quick glance at the yews (Taxus). Those huge, centuries-old trees sometimes seen in graveyards are the common yew (Taxus baccata), but you probably would not recognise it as the originator of the cultivar called ‘Repens Aurea’, a dwarf, prostrate, golden-leaved form; nor of ‘Semperaurea’, which makes a dense bush clothed with bright gold and cream foliage in winter and summer. Those imposing Irish yews that form a neat column of erect branches are T. baccata ‘Fastigiata’. The form ‘Fastigiata Aube gold recedes to the leaf margins only. For a tiny, very narrow, golden pillar that will shine out in the dark winter days, the extremely slow-growing, dwarf T. b. ‘Standishii’ would fit the bill in any size of garden. It takes about 10 seasons to reach the dizzy height of 1m (3-1/4ft).

Bushes that also maintain more than a hint of sun in their year-round colouring are to be found among the cultivars of the arborvitae (Thuja occidentalis). ‘Rheingold’ makes a feathery looking, rather pointed bush. In summer it is a pale yellow, but this changes to a rich old gold in the winter months to enliven the dullest of days. Slow growing, it may take 20 years to reach 2m (6-1/2ft). Another is ‘Aurea Nana’, which holds its foliage sprays on edge, forming a fat, oval, yellow-green bush; even slower to develop, it may take a decade to top 600 mm (2 ft). Somewhat freer growing, ‘Conspicua’ may reach 4 m (13 ft) in about 12 years. Conical in shape, it makes a dense bush which holds its golden colour through the winter.

Although all the conifers so far mentioned have been upright or spreading, bushy or prostrate, they can also offer one or two very attractive trees of weeping appearance. The

Nootka cypress (Chamaecyparis nootkatensis ‘Pendula’) is particularly spectacular as a young tree, when its outstretched branches radiating from an upright trunk are festooned with hanging branchlets and foliage.

Chamaecyparis lawsonianaThe coffin juniper (Juniperus recurva coxii) is a true weeper, its branches sweeping grace-fully downwards from the central stem. It is one of those conifers that can eventually grow very tall, but seems to be so slow growing that you could enjoy it for perhaps half a lifetime in quite a small garden before it had to be taken out.

One of the most spectacular conifers, although regrettably not one of the easiest to establish and certainly not one for a windy site, is Brewer’s spruce (Picea breweriana). Its basic outline is conical, with downward-curving branches that are fringed with long hanging branchlets of blue-green foliage. It makes a spectacular specimen tree and although its ultimate size is large, it is slow to develop and may well reach no higher than 2 m (6 ft) in its first 10 years of life.

A much easier to grow conifer of weeping appearance that thrives in sun or shade is the Westfelton yew (Taxus baccata ‘Dovastonii’). This makes an attractive small tree with horizontal branches that are festooned with weeping branchlets; the foliage is very deep green. ‘Dovastonii Aurea’ is of similar appearance but with yellow-edged leaves.

Maintenance

Most conifers grow well in most types of soil, provided that they are neither shallow nor dry. Yews thrive where there is chalk and on quite thin soils, too, while the junipers can do well in surprisingly dry, sandy and chalky soils. The thujas, on the other hand, show a preference for a much heavier rooting medium and a high rainfall area.

The great majority of conifers should be sited so that they enjoy plenty of sun. If kept in the shade of other trees they tend to elongate too quickly and the yellow forms, especially, lose colour and become more green as the shade deepens.

Most conifers require little in the way of pruning or training, taking on the various shapes quite naturally. The prostrate forms are often better if the leading shoots are lightly pruned to encourage them to thicken out rather than to wander too far afield at first. If an all-green shoot appears on a coloured-leaved form it must be cut out entirely. Occasionally a conifer with a distinct trunk may develop two or more shoots at the apex instead of just a single leading shoot. If left to grow these would ruin the tree’s shape, and all but the best shoots should be shortened or removed. It is sometimes necessary, with a young tree, to tie the leading shoot to a cane to keep it straight and encourage upward development for two or three seasons.

In common with other evergreens, all these plants are either pot-grown or specially treated in the nursery to encourage the formation of a dense, fibrous root system so that they can be transplanted with a large amount of their roots encased in a ball of soil. Every effort must be made to keep this ball of roots and soil intact at planting time. To help keep it moist, wet peat should be packed around it when planting and, after the soil is trodden firm around it, the site should be liberally watered, and then covered with a 50 mm (2 in) mulch of peat. Check occasionally to see that the root ball does not dry out while new roots are pushing out into the surrounding soil, and water around the base of the plant if necessary to rewet it. Such care is needed because, while all plants inevitably lose some of their roots system when they are transplanted, conifers, like all evergreens, continue to lose moisture from their leaves – and this has to be made good by the remaining roots if the plants are not to suffer a setback.

One of the biggest enemies of newly transplanted conifers is a dry wind, which desiccates the plants before they can make sufficient new roots to supply their full water needs. It pays, therefore, to screen them for a few weeks from drying winds with sacking or sheet polythene arranged around stakes or canes. You can also speed their establishment, and increase the growth rate in the first year, if you wet their foliage by syringing or spraying them overhead with water on the evenings of dry days.

Another enemy of conifers, particularly those with upright-growing branches, is snow, which can weigh them down and spoil their shape, or even snap off whole branches. After a heavy fall it is worth knocking off as much snow as you can from your conifers with a broom. And to avoid the upright ones being spoiled, it pays to ring them round with stout wire in the autumn to prevent the possibility of their branches splaying out under the additional weight.

05. July 2013 by admin
Categories: Evergreen, Trees and Shrubs | Tags: | Comments Off on Garden Conifers

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