Planting, Maintenance and Pruning of Ornamental Shrubs
PLANTING, MAINTENANCE AND PRUNING OF SHRUBS
Seedlings which are three to four years old are best for planting out, though a great deal depends, of course, on the growth and vigour of the shrub and on the method of propagation. In general, seedlings raised from seed are usually not as strong as those raised from cuttings. In both cases, however, it is essential that they have a well-developed root system. Before planting, the roots should be thinned — only the stronger roots are shortened, the fibrous ones are left untouched. The above-ground part of the plant is generally cut back to 10, 15 to 20cm (4 to 8in), depending on the height of the given species and its powers of rejuvenation, with at least three or four buds left on the remaining shoots. Cutting back of the top parts prevents excessive evaporation at a time when the root system is still not fully able to make up for the loss of water.
The best time to plant ornamental shrubs, except for those grown in containers which can go in at any time, is spring, when theis fully thawed and can be easily worked and before the seedlings have started to grow. The size of the hole depends on the size of the root system; as a rule, it is between 30 and 50cm (12 and 20in) deep and wide, unless the seedling is too large. The bottom of the hole should be covered with a layer of well-rotted manure for more demanding plants such as or clematis, or composted soil for less demanding plants, or peat or a mixture of peat and compost for heath plants. The roots are spread out over this layer and then the hole is gradually filled with soil, which should be pressed down as the hole is filled so that the plant stands firm. The depth of planting should be such that the root neck is covered with soil; the mark of the previous planting level can usually be seen on the stem. The plant should be watered in, and watering should be repeated daily unless the weather is rainy.
Nowadays sprinkling systems are becoming very popular for gardens. Only certain shrub species such as sea buckthorn tolerate exceptionally long periods of drought. Plants should be watered or sprayed during periods of dry weather in late spring and summer. Periods of drought in autumn are not so damaging.
For ornamental shrubs to grow well they must be kept regularly fed once every two or three years. Various proprietary feeds are available on the market, and these should be applied according to the manufacturer’s instructions. Organic or natural fertilizers (farmyard manure and) should also be applied now and then; for some ornamental shrubs such as roses and rhododendrons they are even a must. Hoeing and weeding are unnecessary where shrubs are surrounded by turf or carpeting plants or where they are so dense at the base that they shade the soil and prevent the spread of weeds.
Pruning helps to control the growth of shrubs as well as affecting the abundance of. For this purpose shrubs are divided into two groups. The first bears blooms on the previous year’s growth or older shoots and flowers in early spring, either before or at the same time, or shortly after, putting out leaves. This group includes, for example, berberis, cotoneaster, crataegus, cornus, cytisus, chaenomeles, deutzia, daphne, magnolia, ribes, syringa, Viburnum lantana and certain species of lonicera and spiraea. These are pruned lightly during the growth period immediately after flowering. As a rule, only the faded flower shoots are removed, or else the flower stalks. The shrubs should not be pruned in winter, though in some cases weak and unruly shoots may be removed.
The second group flowers later — in late spring, early summer or even later than that and when they are in full leaf. These are pruned in winter or early spring. They bear blooms on the new shoots produced during the current season so that latemeans loss of that year’s crop of flowers. Here the shoots are cut back to about half their length. This group includes, for example, caragana, calycanthus, colutea, cytisus, diervilla, , , philadelphus, , rubus, , sambucus, viburnum, certain species of spiraea and cornus and . Only a few ornamental shrubs require no pruning at all, for example, rhododendron.
Besides regular pruning ornamental shrubs must also be rejuvenated occasionally, when they are too tall and spindly or of unattractive habit. All strong branches are cut off 20 to 50cm (8 to 20in) above the ground, in some cases close to the ground. To keep shrubs healthy it is also important to thin them out by removing dry, diseased and weak branches and about two or three of the strongest branches from the centre. This serves to make the shrub less dense and also more shapely.