HOME GARDENS

Bay of Plenty Beacon, Volume 12, Issue 13, 16 January 1948, Page 6

HOME GARDENS

(By J. W. Goodwin, N.D.H. (N.Z.), F.R.H.S. Massey Agricultural College.)

UTILITY OF A ROCK GARDEN A Rock Garden is probably the most useful and attractive feature that may be included in any garden plan. If it is well constructed there are congenial homes.for a very wide range of plants, many of which would otherwise die and become lost to gardens. In some gardens, steep slopes and irregularities in the contour of the ground are not suitable for lawns or bedding, and yet they provide a natural site for a rock garden. By selecting the showiest and longest flowering species and massing them in the larger pockets, a rock garden may be gay and colourful throughout the year. There is a minimum of maintenance if weeds are prevented from seeding, and providing that sorrel, twitches and similar plants are not permitted to gain a hold. Cultivation may be attended to at all times by placing stepping on moraines or drifts. The pockets may be replaced with new compost when replanting, or top-dressed annually, but otherwise there is very little work involved in a well-made garden.

There are many types of rock gardens and the range of plants grown may be determined by the lay of the land and the construction. Should the land face north, then the great majority of suitable plants must be able to withstand dry conditions—most of the dianthus, allysum saxatile, aubretia, phlox subulata and similar plants; many of the South African bulbous plants and other bulbs which flower early and ripen their leaves before the fierce summer heat. Bulbs will always leave a gap, but they may be followed with dwarf annuals suited to the position, such as linaria, nolana, anagalis, etc. Only in the drifts or screes will it be possible to grow moisture-lov-ing plants, whilst shade-lovers will be limited to the shady side of rocks or dwarf shrubs. Trees and Shrubs Unwelcome

On no account should shrubs or trees, whose roots are robbers, be planted near a rock garden. Their roots will travel long distances and rob plants of moisture at the critical time of the year, and the area will become suitable only for cacti, succulents and the hardiest of drought-resistant plants. Should the site face even slightly away from the sun a wider range of plants may be grown. There will be well-drained shady corners or crevices, whilst lower down there will be moister shady areas. There will be exposed, sheltered and sunny places, whilst always the roots of plants will be able to seek the cool, moist soil beneath the rocks.

The aim, when growing true alpine plants, is to provide as nearly as possible the conditions that occur in nature. Although lowland climatic conditions cannot replace alpine ones, similar physical conditions can be provided. In alpine regions, such as those of the Swiss, Maritime, Cottian, Graian, Pennine, Bernina, Himalayan, Siberian and Scandinavia Alps, as well as those of New Zealand and America, plants have to endure long periods of low temperature, often be snow-covered, violent winds, rain and dust. Moisture is completely frozen up in the winter, and is excessive in the summer when the snows thaw. In the Balkan, Italian and Dolomite Alps there is excessive moisture in the spring followed by a period of drought. Consequently, the majority of species from these regions require an abundance of water in the spring and a hot dry summer position to ensure the ripening that naturally takes place. Plants from our own and similar alps, at high altitudes,.require abundant moisture in the summer and very little in the winter. For these it is essential to have good drainage, and the rocks should be so placed that they conserve moisture and enable the roots to grow under them for protection. The favourite haunt of many rockloving plants is the scree slope on which drainage is rapid and stagnation impossible. The artificial scree is an important section, of our modern rock gardens. Many plants succeed there which would perish under ordinary conditions. A gentlysloping drift is most suitable, and the soil must be free and rather spongy. Half-inch metal chips and leaf mould may be used to open up the soil. The depth of material will vary for different plants, but the top soil should consist of 1 part loam, 1 part 2-inch metal chips, 1 part leaf .mould or spagnum moss. The surface itself should consist of one inch or more of h -inch chips, which will keep the soil cool and conserve moisture. It will also drain away excess moisture from tender crowns or woolly leaves of plants and help to prevent weed growth. Smaller plants should always be planted on the margins of the scree or near rocks.

Crevice plants must not be placed where water will drip on them from rocks above. Planted on their sides, with the roots extending back to the soil behind and their leaves hugging the rock face, they are quite

happy. Some species select similar positions in nature to give them shade, others to prevent moisture lodging among the leaves and crowns. ‘Borderline’ Plants Alpine meadows supply perhaps the greatest range of plants, and the majority of these are found on rather peaty soils. The general rock garden soil should be made free by" the incorporation of sand or metal chips and leaf mould or peat. Its water-holding capacity may also be improved by the two last-mentioned. Special composts may be prepared for special plants. Many plants grown on rock gardens in one district are quite good border plants in another. The smaller plants and bulbs are easily lost if grown in mixed borders. They are much more permanent and give better displays, when planted among the alpines. Similarly, many of the choice dwarf shrubs prefer the shelter of a rock, and the evergreens help to furnish the area in winter time when many plants have died down. Personally, I always establish in a selected corner of the rock garden new plants which are reputed to be difficult. The chances of success are considerably greater and, once acclimatised, they may, if vigorous, be tried in a similar position in the mixed or herbaceous borders.

The use of rocks in the garden, even if there are only a few of them scattered among choice dwarf shrubs or lilies, will always give character to a gafden and provide a natural setting the plants. Probably the best method is to imitate a fall of rock from a cliff above. Several rocks may be grouped close together, other large ones may be widely dispersed, with smaller stones scattered here and there throughout. For an alpipe garden an outcrop or series of outcrops of rocks may form the backbone, and the crests and drifts developed naturally around these. The stones should be weathered and rather round in shape. Rocks which are rather flat may be used if available, but are more difficult to arrange naturally. These are, however, the best type for cliff faces and crevices. 'A Mirror Up To Nature

The best method in building is to peg out with 3ft. stakes. These should indicate the highest rock outcrops or spurs; shorter stakes may be used to indicate the. tops of the lower spurs and crests. Always try to imitate a natural outcrop of rock, with drifts of rocks spreading out to the lower levels or valleys between crops. If the area is comparatively uniform, it will be necessary to create drifts and valleys. This may be done by throwing soil up round the stakes from the valleys in between. This will ensure a good depth of top soil among the rocks, and the bottom of small valleys may be filled with a prepared screen mixture, or perhaps a rocky poolwith the scree sloping down on one side, and a cliff bn the side facing east or south. Once the outline is made in soil, stones may be scattered up the small valleys or drifts, until at the bottom of the slope the more solid groups of rocks form level pockets. Above these, another natural group raises the elevation still higher—not in regular terrace formation, but consisting of several groups at different levels, indicating the inward slope of a natural stratum. The majority of stones should be buried about two-thirds. They will be firm, and any broken faces or irregularities may be hidden. By setting the stones with the longer upper surface sloping backwards, most of the rain percolates back into the pocket behind, and down under the rock to the waiting roots. If the long sloping surface was facing outwards, the moisture would be drained off, probably following a channel in the rock and washing out some treasured plant below. The whole area would also look flat and unnatural, as most natural formations incline inwards. Most of the pockets themselves should be reasonably level so that all rainfall will penetrate evenly over the surface. They should not be too full, but rather like the natural accumulation of soil washed down from above and lodging among the lower outcrops and natural rockfalls. If the soil is reasonably good, pockets may be excavated and the condition improved to suit the particular plant to be grown.

The rock gardener is probably a keener enthusiast than the gardener who specialises in a popular flower. The variety of plants that may respond to. his skill is legion. They are less often seen than they should be, and always attract attention and admiration. The satisfaction in growing a rare and difficult plant will more than compensate for the extra work incurred in making a really good rock garden.