Heaths in the Flower Garden

New Zealand Journal of Agriculture, Volume 98, Issue 4, 15 April 1959, Page 401

Heaths in the Flower Garden

HEATHS and heathers are I I both plants of the Erica family and in this article J. P. Salinger, Horticulturist, Department of Agriculture, Wellington, describes the species of erica and their cultivation in the flower garden. Most are useful and easily grown garden plants providing a bright splash of colour over a period ana being particularly useful for decorative work. THE heaths or ericas are a widely distributed group of plants which occur naturally in Europe and South Africa. There are several related plants with a similar habit in Europe, notably calluna or ling and Irish heath. In Australia and New Zealand none of these plants is native, the nearest related being epacris, gaul-

theria, and pernettya. These have similar cultural requirements to ericas and so are included in the description of heaths which are cultivated in our gardens. As with many other plants grown in our gardens there are many varieties of the European species but few varieties of those from the Southern Hemisphere and this will obviously affect the choice and method of propagation of these plants. The European ones are very hardy and unsuitable for the warmest areas while the South African heaths are half hardy and grow better in the warmer areas. In parts of New Zealand some ericas and related plants have become naturalised or are even considered weeds. In Tongariro National Park ling (Calluna vulgaris) covers large areas of unimproved tussock country. In the north Erica baccans grows wild but is not a troublesome weed, while Spanish heath (Erica lusitanica) and the tree heath (E. arboreal are weeds

in parts of Marlborough and Nelson provinces, but are found wild only occasionally elsewhere. It is doubtful whether any of them will prove as aggressive as broom or gorse, but as the plants are not easily killed by chemical methods of weed control, their spread to agricultural land should be watched carefully. Use in the Garden Most of the ericas are dwarf or medium height, only a few species growing taller than 6 ft, and even these may be kept quite small if the flowers are gathered for the house and the young shoots trimmed back.

Though individual plants may be quite attractive, groups of one variety are much more effective, especially with the paler colours. They may be planted toward the front of a shrub or mixed border among taller, more upright plants or, if plenty of plants are available, they may be used as ground cover under deciduous shrubs and trees. The dwarf types are excellent for rock gardens or covering a bank, and all of them are suitable for interplanting between evergreen azaleas and spreading varieties of camellias and for providing soil protection to stem rooting lilies. Soil Requirements The essential feature of heath culture is that the soil should be acid or. if nearly neutral, that no free lime should be present in the soil; one species, Erica carnea, will tolerate less acid conditions than the others, but even this will not thrive in alkaline soils. Soil acidity can be increased by applying sulphur at 1 oz per sq. yd., but this should not be necessary, especially if acidifying fertilisers such as sulphate of ammonia are used. The soil should be reasonably well drained; the texture of poorly drained soils can be improved by incorporating peat, leaf mould, or rotted sawdust and light. soils in drier areas can be improved with well rotted compost. In general, though, heaths do not need organic matter in the soil and

benefit more by mulching, with rotted compost or sawdust to which 4 oz of sulphate of ammonia per square yard is added. The only additional manuring is the application of blood and bone at 6 oz per sq. yd. in spring or a mixture of equal parts of sulphate of ammonia and superphosphate at 4 oz per sq. yd. As with other plants of this family certain beneficial fungi known collectively as Mycorrhiza penetrate the roots of the heaths and assist in the plants’ nutrition. Planting Heaths can be planted at any time from April until the end of September. Plants bought in pots may be planted even earlier or later, as they are frequently offered for sale in flower and will grow on quite satisfactorily if they are carefully watered in when they are planted and protected by sacking or plastic sheet from excessive wind or sun. Newly set out plants do not need frequent watering; they will, benefit by two or three heavy waterings at intervals in dry weather and a light damping between the waterings. Before setting out plants it is important to see that the root ball is thoroughly moist; the bushy, fibrous , roots can completely penetrate the ball of soil round them and if this is dry, it is difficult to moisten again once the plants are in the ground. If the degree of dampness of the soil and roots is in doubt, the ball should be

stood in a bucket of water for half an hour before planting. Where roots are wrapped in scrim, this should not be removed completely until planting. It is better to set out plants with moist roots in drier soil rather than plant a dry root ball in wet soil. Plants should be set out with the top of the root ball just below the soil surface. Maintenance The soil round establishing plants should be lightly hoed, but the surface never penetrated more than half an inch, as the roots develop near the surface; a mulch of well rotted organic matter can be applied in mid December the first year and added to each subsequent year so that soil cultivation is kept to a minimum and weeds suppressed. Heaths require light annual pruning. Each year after flowering the tips of the season’s growth should be shortened back slightly and the old flower heads brushed off with the hand unless they are required for seed. Many varieties do not produce new growth if cut back into older wood, but the cutting of sprays of flowers for decoration will not harm the plants and in fact is a form of pruning.

Heaths are remarkably free of pests and diseases, though they • are occasionally killed by soil borne fungous diseases such as phytophthora. The damage can be restricted by drenching the soil with copper oxychloride at 1 lb to 10 gallons of water applied at 2 gallons per sq. yd., but plants will not tolerate repeated applications of this copper soil drench. The dwarfer varieties harbour snails, which do not seem to attack the heaths themselves; so slug bait should be used round them, if other plants are being eaten. Propagation -■ Heaths are propagated from cuttings, layers, and seeds. Named varieties are raised only by vegetative methods; this applies especially to varieties of the European species. Vegetative Propagation All heaths can be raised from cuttings taken from the young tips of the shoots in January or February; small side shoots with a heel of older wood may also be used. They should be inserted in a compost of equal parts of peat or leaf mould and coarse sand. The usual method is to insert the cuttings round the edge of a 4 or 5 in.

clay pot. This should be well watered and then placed in a larger pot or box which is covered with a sheet of glass and placed in a warm place shaded from direct sunshine. A moist atmosphere must be maintained, but the compost must not be kept too wet. When rooting has started there will be a definite development of new growth at the growing point. The atmosphere can now be drier and the cuttings transplanted. As the roots are thin and hairy, the whole pot should be carefully tipped out and the cuttings separated, each with a small amount of compost round the roots. These small plants should then be potted up singly in ■ small pots of the same mixture to which 4 oz of bone meal per bushel of soil is added. The pots should be set out in a sheltered position. Some of the European species can be propagated from larger cuttings taken in April or early May and set in sandy soil in a cold frame. Many of the dwarfer species will layer naturally if sandy soil is worked in round the bases of the plants in spring. The rooted side shoots are cut off and transplanted in late April or May.

Raising from Seed Many of the South African species can be raised from seed; the flowers should be collected when dry, care being taken to pick the seed capsule as well. These should be placed in a container in the sun and the fine seed will then fall out. This may be cleaned of other plant material by shaking through a fine sieve on to a sheet of white paper. The name of the plant should be written on the paper if the seed of more than one species is being collected. The best times for sowing seed are late February to early May or in September. Seed boxes or pots should be used and plenty of drainage material placed in the bottom. A suitable soil mixture is equal parts of sterilised loam, peat, or leaf mould and coarse sand or pumice. The container should be watered before sowing and the seed lightly and evenly sown over the surface. It should be covered with a very thin layer of the sand or pumice or sphagnum moss rubbed through a fine sieve. The container should be covered with a sheet of paper, a pane of glass, or a piece of asbestos sheeting. Except where paper is used, one corner of the covering material should be raised

slightly with a small block of wood to prevent excessive condensation. The container should be placed in a shaded frame or greenhouse and watered when necessary by standing in a trough of water. Germination is slow, usually about 6 weeks. When it takes place the covering should be removed. When the plants are J to 1 in. high they should be transplanted into other boxes or very small pots. Great care is needed as the roots are surprisingly long for such small plants. After they are transplanted they should be watered in and set in a shaded place until they are growing away, when they can be grown on in a more open position, provided some shade is given in hot weather with scrim or laths placed over the area. When well rooted and growing satisfactorily the plants should be set out in a nursery bed of open soil in a partially shaded position before being

planted out finally when about 1 year old.