Native Trees and Shrubs for the Flower Garden

New Zealand Journal of Agriculture, Volume 90, Issue 4, 15 April 1955, Page 430

Native Trees and Shrubs for the Flower Garden

DURING the last few years New Zealand native trees and shrubs have become increasingly popular with gardeners as their value and uses have become better known. Though it cannot be denied that most of them are not as spectacular as many exotics, they have their place in the garden. In this article J. S. Say, Horticulturist, Department of Agriculture, Auckland, discusses their use in the garden and describes some of the newer varieties which could be more generally grown. The section on flower garden work for May is by M. Joanna Lockie, Horticultural Instructor, Department of Agriculture, Auckland.

A WELL-KEPT and well-laid-out shrub border is an asset to any garden. It will provide colour and interest throughout the year and compared with the work needed in keeping a herbaceous border or beds of annuals in order requires little attention. New Zealand has a number of shrubs which can be used to advantage. Comparatively few native shrubs have showy flowers and an all-native border has to depend very largely on variations in colour, shape, and texture of leaves for its effect. Though such a border has points of interest for brief periods throughout the year when particular plants are in flower, it remains for the most part unchanging and tends to become monotonous. By combining the best of our native shrubs with the best from other countries it is possible to plant a border which is ever changing and can provide interest the year round. It is

often claimed that mixing New Zealand shrubs with exotics gives an incongruous effect and should not be done. Cotoneasters from the Himalayas, berberis from Japan, ceanothus from California, and prostantheras from Australia are mixed without hesitation and it seems unreasonable not to make use of New Zealand’s own good shrubs with those from overseas to make a first-class border. Since the first coloured manukas were discovered about 40 years ago a great many improved varieties have been introduced. During the last few years a number of excellent varieties, some produced by American hybridisers, have come on the market. Among the newer varieties are Leptospermum scoparium var. sandersi, a winter flowering form with large pink flowers deepening at the centre; var. tancredi with deep rose pink semi-double flowers; Red Damask with red double flowers and bronze foliage;

Scarlet Carnival, with red double flowers; and Ruby Glow, blood-red double flowers. Hebes (shrubby veronicas) may be obtained in a wide range of colours, heights, and leaf forms. Three of the showiest are Hebe speciosa (violet purple) and its varieties La Seduisante (rosy purple) and Violet Meikle (violet blue). Their main flowering season is in spring, but they frequently have a few flowers throughout autumn and winter. They grow to about 3ft. H. earned forms a smaller bush about 2ft. high and has showy pink flowers in summer. C Han thus puniceus (kaka beak) is known to all gardeners. Though it

produces a great wealth of flowers, they are often hidden by the spreading and drooping branches. It is much more effective if it is trained as a standard. This is done by removing all the side growths from a young plant, thus forcing all the strength into the main stem, which should be tied to a stake. The plant should be grown on with this one leader until it is about 2ft. 6in. high, when the tip is pinched out and the side growths on the top few inches are allowed to develop. Clianthus is also very effective when grown on the top of a bank where it can be seen from below. For autumn and winter berries corokias are very useful. C. cotoneaster forms a dense mass of black interlacing twigs with small leaves and masses of small red berries. C. cheesemani is similar but with greyish leaves and yellow berries. C. macrocarpa and C. buddleoides are more strongly growing with erect, less dense growth. Both have leaves with silvery backs and large red and yellow berries respectively. In spring they all have masses of small yellow flowers.

In a shrub border consisting entirely of natives considerable use has to be made of shrubs With coloured and variegated foliage to give a little colour to what otherwise can be a rather sombre green mass. A number of variegated forms of pittosporum are now available. P. crassifolium, P. tenuifolium, and P. eugenioides all have varieties with creamy yellow variegations. In addition P. tenuifolium has three other very good varieties, garnetti,' with cream and deep pink markings, sandersi, an improved form of garnetti, and purpureum with red-bronze leaves. A shrub suitable for the back of a large shrub border is Brachyglottis repanda purpurea (purple rangiora). Its large leaves are dark purple above and silvery white beneath, making it very attractive, especially when a slight breeze is disturbing the leaves. It is advisable to give it some protection from heavy frosts when young. In early spring it produces large heads of creamy flowers with a honey scent.

Some of the newer varieties of New Zealand flax have little resemblance to the plant with coarse dark green leaves which grows in many swamps. Phormium tenax var. rubrum has rich coppery bronze leaves and var. tricolor has creamy yellow variegations with a red edge. Both grow to only 3ft. to 4ft. and have slender, pliant leaves which make them very useful for floral work.

One of the most brightly coloured shrubs is the variegated form of taupata (Coprosma baueri variegata'), which has yellow and green shining leaves. It is not such a robust grower as the ordinary taupata and has a slightly pendulous habit of growth. A few plants with silver or grey foliage are always effective in a shrub border. For this purpose Senecio greyi and S. compactus are suitable and have the added attraction of yellow, daisy-like

flowers. Another greyish shrub is Pachystegia insignis. It has large leathery leaves, bright green and smooth above and a dense white furriness below. The flowers, held well above the foliage, are white and daisylike and are good for cutting. Besides containing shrubs with coloured and variegated leaves the border can be made more interesting by using shrubs with leaves of various shapes, sizes, and textures. For example, the large coarse leaves of parapara (Pisonia brunoniana) or rangiora are an ideal foil for the light, dainty, shining leaves of Pittosporum eugenioides, P. tenuifolium, and their varieties. Two interesting forms of Macropiper excelsum (kawakawa or New Zealand pepper) are now available. M. excelsum variegata has an irregular creamy yellow mark in the centre of the leaves and variety psittacorum has

very large, heart shaped leaves which are lighter in texture and paler green than the ordinary type. Its habit of growth is also more upright. Both will grow in open situations but are better under fairly heavy shade. Pseudopanax is another genus in which there are a number of attractive species, hybrids, and forms. With P. crassifolium (lancewood) the juvenile leaves are long and narrow and very different from the compound leaves of the adult tree. One of the best species is P. discolor, a compact, much-branched shrub with rich bronze foliage. Hedges Of the native shrubs used for hedges pittosporums are the most popular and many gardeners regard them as the only suitable ones. However, there are a number of others which will make useful and attractive hedges.

The coloured forms of manuka (Leptospermum scoparium) will make a very colourful hedge which can be kept compact and clothed to the . base if they are trained from the time they are planted. Initial training should consist of pinching out the growing tips to encourage bushy growth, but later . hedge shears can be used. Corokia cotoneaster is particularly suitable, especially for the seaside, but is rather slow growing. The . other corokias can be used, but they do not form such a satisfactory hedge. For a dwarf hedge or low division in the garden some of the hebes are excellent, but are very seldom used. Hebe speciosa and its varieties form rounded, compact plants about 3ft. high and about 3ft. across and if planted 18in. apart, form a low hedge with a rounded top. Hebe hedges can usually be kept in shape by removing the old flower heads, but an occasional trimming with secateurs may be necessary if there is any tendency to become straggly. An attractive edging which needs little attention can be made with some of the small-leaved types of hebe such as H. buxifolia and H. diosmaefolia. In certain positions a hedge with a bronze appearance is an advantage, especially where it is used as a contrasting background to plants with light coloured foliage and flowers. Myrtus bullata (ramarama) can be formed into a good hedge. Its leaves are small, very glossy, and have a reddish-bronze tinge. During summer it has small white flowers followed by dark red berries. It is rather sus-

ceptible to attacks by scale insects, but these can be controlled by spraying with summer oil. Some manukas also have bronze foliage. Nurserymen are sometimes unable to supply in hedging quantities plants such as those mentioned, because they are outside the normal demand, and intending growers would be advised to place their orders well in advance.

All the shrubs mentioned for hedges can be propagated easily by the home gardener. Seeds from the coloured varieties of manuka usually germinate readily and though they ,do not come absolutely true to type, most are sufficiently alike to make a uniform hedge. Seedlings which are obviously different from the majority can be set aside. Those with green leaves usually have flowers which are white or very pale pink and can be discarded, but those with dark leaves, especially if large, are worth keeping, as the flowers will probably be of very good colour. Corokias grow easily, from seed, but it is. sometimes difficult to get an even line for hedging. Corokias hybridise very easily and if different species are growing in the same vicinity, it is likely that cross-pollination has taken place and the seedlings will show . a big variation in growth habit and in the size, colour, and shape of the leaves and berries. Even when seed is collected from an isolated specimen there may be some variation in the seedlings, as the parent may itself .be a hybrid. Raising, corokias from seed can be very, interesting, ..for if seed is collected from a group of different species, often a very good form will appear among the seedlings. Myrtus bullata also comes quite easily from seed. All the hebes can be raised from cuttings made from young non-flowering shoots 3in. to 4in. long. They can be rooted at any time of the year when suitable cutting material is available. '

Specimen Trees

The numbers of large trees planted in the middle of front lawns show that many gardeners apparently like to have a specimen tree. Trees of this type are very difficult to site correctly,

especially in small suburban gardens, and very rarely is the middle of the front lawn the right place. When the planting of a specimen tree is being considered it should be visualised in its mature form. Then the gardener can make sure that it has room to develop and that it will not cast shade where it is not wanted or will not interfere with the view. The fact that a specimen tree has to have the top lopped off because it is touching the power lines or has to have the side trimmed or the lower branches removed because they are obstructing a pathway is a sign that someone has planted without sufficient thought. The neighbours’ gardens, views, and sunshine should also be considered. ™ + fnrpst trees are Most New harden too large for the average to g and should be left for f °® e h t | s sections or planted in fa J™ h x f where space* s not so limited. g O of the most beautiful trees E edrus planting is the kawaka ( > wh°se uhimate h g P to 50ft. Its symmetrica , ? y k habit and pale green leaves ideal for this purpose , ° trees suitable for planting w . . is room : are nmu, Kara > P ’ rewarewa, kohekohe, t;ot ar »> , pohutukawa, a “ d 1 o g kauri is often recommend , , situations, it will not st p g the drv spell to 25ft high, J ed during the dry spell m Auckland in th • Two species which have produced attractive varieties with variegated leaves in recent years are Coryno-

carpus laevigata (karaka) and (Metrosideros excelsa (pohutukawa). One form of the karaka has silver markings throughout the leaves and the other a yellow edge.. Several forms of pohutukawa with creamy yellow variegations and also a yellow flowered variety are available. None of these variegated forms is as vigorous as the ordinary kinds. For smar sections there are a number of suitable trees which because of their shape, size, and attractive leaves lend themselves to specimen planting. The hoherias (lacebarks) are good. H. populnea forms a shapely tree which is smothered in white flowers in autumn and its W o variegated varieties, alba variegata and aurea variegata, are also suitable but not quite so hardy ’ H ' osbornei is another species which flowers freely. The flowers are white with purple samen s and the under surfaces of the leaves also have a purplish appearance. In colder climates Hoheria (Gaya) lyalli is more suitable than the others because of its hardiness; in fact it does not like the warmer parts. During summer it bears masses of white cherry-like flowers and in winter loses most of its leaves, for it is one of the few deciduous or i-deciduous native trees. Closely related to the hoherias is another deciduous tree, Plagzanthus betulinus (ribbonwood). Its leaves are much softer than those of the hoherias< A tree rare - n itg wild state but becoming very common in gardens is Meryta sinclairi (puka), which bears dark green shining leaves up to 18in.

long and 9in. wide. It makes a good specimen, but owing to its coarse appearance needs very careful placing and for this reason is not suitable for the average small garden. Probably the best-known and showiest of New Zealand trees are the kowhais (Sophora spp.) . They make good specimen trees, but it should be remembered that the two most commonly grown species, S. tetraptera and S. microphylla, grow to a height of 30ft. and sometimes higher. For the home garden S. treadwelli is often more suitable, as it is not so tall. The foliage is very small, but . the flowers are large. Tub Plants Tub plants are becoming very popular and there are many laces where they C an be used to good effect such as a pa j r standing at the base of the seS leading to the front door or on a paved area against the wall of the house. Kawaka, though it will grow into a large tree if planted in the open ground, makes a very good tub plant which, with a little care, can be kept healthy and clothed to the base, Ri m us, kauris, and pohutukawas are other large trees which do not object to being confined in tubs and make goo d specimens. Of the smaller trees or large shrubs Pittosporum eugenioides variegata is excellent and for something quick growing but not long lasting the purple leaved akeake (Dodonaea viscosa purpurea) is useful, New Zealand flax (Phormium' tenax) also makes a good tub plant, the coloured varieties being particularly suitable.

Rock Gardens Few rock garden shrubs can compare with the delightful dwarf form of manuka, Leptospermum scoparium nanum. Though the plant is small, usually not more than 6in. high, the flowers are large and almost completely hide the bronze tinted foliage when in full bloom. They are pale pink with a darker central zone. Other dwarf shrubs suitable for the rock garden are some of the small hebes such as H. lycopodioides, which belongs to the whipcord section and has small, scale-like leaves. The plant has a rich bronze appearance with dense, heads of white flowers on the tips of the stems. H. vernicosa, H. gracillima, H. decumbens, and H. bidwilli are also suitable. A scrambling shrub which can be used in the rock garden is the little Fuchsia procumbens. The flowers are small and inconspicuous but are very interesting, for they are held erect and are rather strangely coloured. The tube is yellow, the sepals green tipped with purple, and the stamens light blue. The berries are large, red, and very showy. This fuchsia also makes an attractive hanging basket plant.

Cultivation and Training

Two common misconceptions about New Zealand’s native trees and shrubs are that they will not stand manures or fertilisers and that' they cannot be pruned. They should be given exactly the same treatment and attention as any other tree, both at planting time and after. They react most favourably to blood and bone, which should be incorporated in the soil when planting and as a topdressing later.

Most native trees and shrubs are not particular about the type of soil and will grow well on light or heavy soils provided drainage is good. It is most important that the soils should not dry out in summer, and for the first year or two especially watering should not be neglected. At all times a good mulch of compost or well-rotted animal manure, sawdust, or lawn clippings will help to prevent the soil from drying out.

Trees and shrubs which do not grow too large for their position should be selected so that no severe pruning or cutting back is required. Pruning can be done to advantage in a great many cases,' but should be limited to that necessary to keep the tree in shape. Trees should be grown on a single trunk and if double leaders form later, they should be removed at an early stage as should any branches which spoil the symmetry of the tree.

Garden Work for May

Gardening in May really amounts to sprucing up the place in readiness for the days when it is impossible to garden, and unless old perennials are

cut down, stakes removed, and dead

annuals cleared away, the garden looks drear and depressing. Garden hygiene is as important in winter as at any other time of the year. Long rank grass on boundaries or weedy, neglected areas should be tidied so that no cover is left to harbour pests such as slugs, snails, slaters, and green vegetable bugs. This cleaning up exposes hiding places to severe winter conditions, which destroy many pests that otherwise might survive. All diseased plant material, including diseased weeds, should be burnt, but healthy garden waste may be composted. Trees and climbers with branches near or overhanging power or telephone lines should be cut back. Strong winds may snap branches or the weight of rain may cause them to touch the wires.

Annuals Spring flowering annuals and the hardier bedding plants can still be set out in well-drained soil. No organic manure or compost should be applied at this time, but a fertiliser mixture of 4 parts of bonedust and 1 part of sulphate of potash should be worked in before planting at 4oz. per square yard. “Woolly bear” caterpillars on cinerarias can be controlled by dusting regularly with D.D.T. dust. Perennials Once dahlias are cut by frost the blackened tops should be cut back to within 6in. of the ground; any plants known to be severely affected by virus should be lifted and burnt. In districts experiencing heavy frosts the tubers should be lifted and stored in a warm, dry position in a shed or

under a hedge. The position should not be too warm or draughty, as tubers tend to dry out. Where named varieties. are grown the names may be written on the tubers with an indelible pencil or labels may be tied on. D.D.T. should be liberally dusted over stored tubers as a protection against slugs, and an occasional inspection of the tubers should be made to make sure they are still plump and healthy. Any rotting tubers should be removed and destroyed. As soon as plants of chrysanthemum, michaelmas daisy, rudbeckia, and other perennials have finished flowering the tops may be cut away and stakes removed.

The Soil

The soil should be worked up and loosened now before it becomes too wet to handle. Where borders are empty . they may be deeply dug. Lighter cultivation should be carried out around shrubs and perennials. Deep digging too close to plants may damage the finer feeding roots . and may even work the plant loose in the soil. Loosening the soil now allows the beneficial action of frost and rain to do its work of breaking lumps and improving soil structure.

Now is the time to inspect drains to ensure that water can get away quickly after heavy rain. Plants need oxygen about their roots, and where the ground about them is saturated for weeks at a time they are deprived of air. In extreme cases they may be killed, but it is more likely that waterlogging will cause the tips of shrubs to die and growth to be poor in the following season.

Frost Protection

Shrubs known to be frost tender require protection, especially when they are young and becoming established. Adequate protection should be given, but at the same time the plants should be allowed some light and air, and care should be taken to see that the scrim or sacking used does not touch the plant.

Hardwood cuttings may still be made of hardy deciduous shrubs and hardy hedging materials. Cuttings should be made of healthy vigorous growth about as thick as a pencil and 6in. to Bin. long. The important points to watch are that the basal cut is made cleanly, not jagged or bruised by being cut with a blunt knife, and that the cutting is firmly planted.

Shrubs

In warmer districts shrub planting may be carried out while the ground is warm. Shrubs moved now will root rapidly and have a long period in which to establish before the drought of summer. In wet soil or in colder districts planting in May is not very satisfactory, roots often rotting during winter. In these districts planting is better delayed until spring.

Idesia polycarpa

A NATIVE of China and Japan Idesia polycarpa is a handsome and rather spreading tree usually about 20ft. high, but it may eventually reach a height of 50ft. The leaves of this tree are large and heart shaped and are borne on reddish stalks. The leaf blade is often 6in. long and Bin. wide or even larger and is generally smooth and bluish beneath. The leaves are tinted in autumn and fall off the tree in winter to allow the bright red fruit to be seen in all its brilliance. The berries are a little larger than currants and are borne in large, pendant panicles and are sought after for florist work. Idesia polycarpa is one of the most beautiful and brilliantly coloured of all berry trees; a tree with a prolific crop of berries is a sight not easily forgotten. The greenish yellow flowers are borne in large terminal panicles and though perfumed are small and unattractive. Male and female flowers are usually borne on separate trees, and it is necessary to have trees of both sexes if it is desired to have berries on the female trees. Reputable nurserymen usually supply plants of known sex and they should be planted in winter. Young trees should be planted in a well-sheltered but sunny position where they will have room to develop and grow into ornamental specimens. Idesia polycarpa is fairly hardy and should grow in most parts of New Zealand where winters are not unduly severe. It will do well in a variety of soils, but prefers a loamy soil. Propagation: Seed may be sown thinly in boxes under glass in spring; germination is usually quite good. When the seedlings are large enough they should be transplanted into sheltered nursery beds. An excellent compost for seed boxes is made up as follows: 2 parts of good loam (sterilised if possible) I part of peat or leafmould . . . . I part of coarse river sand All parts are by volume. To each bushel of the mixture |oz. of carbonate of lime and l|oz. of superphosphate should be added. In warmer districts seed may be sown in the open. Unfortunately there is no way of telling the sex of seedlings until they flower. Plants of known sex may be raised from cuttings or layers. Cuttings should be taken in November or December and should consist of semi-mature shoots with a heel, and should be planted separately in small pots in the same soil mixture as that recommended for seed sowing. River sand should also be placed at the base of each cutting; the pots should then be plunged in sand under glass and bottom heat is usually necessary. Layering is carried out in spring. The shoots are twisted and pegged down and some river sand placed at the bases of the layers before they are covered with earth; the following spring the layers may be transplanted into a nursery until they are ready for permanent positions.

F. E. WILKIN,

Plant Quarantine Officer,

Department of Agriculture, Wellington