Established Rock Gardens
In the established rock garden the most tiresome chore is probably that of weeding. Nonetheless, it is a job that must be taken seriously for weeds pose a really serious threat to dwarf plants, crowding them for space and competing with them for nutrients and water. It has really been made clear that the eradication of perennial weeds must be a first step in preparing a site for a rock garden. They must be plants, like dandelion and dock, with thick and deep-reaching roots; bulbs, such as some species pf Allium or Oxalis, that produce vast numbers of bulbils; or members of a large group of pernicious weeds including bindweed, clover, couch grass and ground elder that extend their territory by means of runners or stolons.
Spending time to ensure eradication in the initial stages will save subsequent hours of difficult labour. Even when great care has been taken in the preparatory stages, there is still the danger of perennial weeds germinating from seed or being introduced by other means. One of the commonest ways these plants are introduced is a seed or as very young plants with new stock brought into the garden. All bought stock, and for that matter whatever comes by way of a gift from others gardeners, should be closely examined for any sign of weeds growing with the new plant. By keeping alert, it should be possible to remove all perennial weeds at the first sign, even if this may mean risking the sacrifice of a plant with which the weed is entangled. Failure may mean perennial weeds gaining a hold.
They will spread there roots under stones and in crevices; once they are established there may be no alternative to dismantling rockwork to get rid of them. Some of the new weed killers that can be applied to the leaves of weeds offer the hope of a radical improvement in control. Even when sterilized soil has been used in the construction of a rock garden and there is a weed-inhibiting mulch of chippings, annual weeds will eventually appear. Among the most troublesome are annual grass, chickweed, club moss, groundsel and shepherd’s purse. Annual grass is a particular nuisance, with a talent for lodging itself in the heart of choice plants. The earlier weed seedlings are dealt with the better; a major battle has been lost when weeds are mature enough to flower and seed. Working over the rock garden with a hoe at any opportunity will kill weeds before they have a chance to become robust. Selective weed killers can only be used with great caution so that if annual weeds are allowed to get away there may be hours of hand weeding ahead of you. It would be misleading to give the impression that rock garden plants are completely free of diseases but on the whole it is true that they are little troubled. When plants are attacked by viruses and fungi, ruthless elimination is probably the soundest course.
Natural Garden Design
In almost any garden the introduction of water, even on a small scale, adds an attractive dimension. In the rock garden a well placed pool or a sequence of pools with running water can heighten the effect of a wild natural landscape created by the rocks and plants. The addition of water also provides an opportunity to grow numerous plants that complement alpines and rock plants. Re-working an established rock garden to accommodate a water feature may involve the moving of heavy rock and the lifting of established plants.
It is therefore ideal to plan water features as an integral part oft he rock garden right from the beginning. A later addition is so often fitted in where it is likely to cause the least work and this may not be the most visually satisfying solution. pool should have two levels, the main body about 75cm (30ins) deep, and a margin, about 25cm (10ins) deep. It is best situated where it will be in full sun for at least half the day. Construction in concrete is laborious and requires experience to get a really satisfactory result. A leaking pool is worse than no pool at all. Prefabricated fibreglass pools are strong and easy to install although they are somewhat expensive. It is necessary to excavate a hole slightly larger than the pool itself and then to use sand or fine soil as a backing layer to give the pool support. The lip needs to be concealed with an edging of rock to make it look as natural as possible. The least expensive and one of the most satisfactory methods of construction is to use a pool liner, made out pf PVC, for example, laid on a bed of sand spread on the base of the hole. The sand must be free of sharp stones otherwise there is a danger that the liner might be punctured. The rim of such a pool will also need to be disguised by and edging of rock.
If a series of pools are to be connected by running water some form of pumping system will be needed to circulate the water. The installation of electrical equipment, such as a submerged water pump, should be carried out by a qualified electrician. However, these pumps do tend to clog up and so it is important to keep your pool water as clean as possible. The best way to do this is to install oxygenating plants. A pool liner can also be used to form a small bog garden, the ideal companion to the rock pool. The liner should be laid in a hole about 30cm (12ins) deep with drainage holes cut in about 15cm (6ins) from the bottom. The bed can be filled with a loamy compost over turves that have been laid grass-side down. If a pool is to be a feature that really enhances the rock garden, its planting should be on a scale with the rest. the pool itself can be planted with deep-water and marginal water plants. What will give it a really authentic touch are the bog plants surrounding it. These could include some of the moisture-loving astilbes, primulas and ferns, as well as many other beautiful plants.
Rock Garden Plants
Rock garden plants are of such variety that some can be found to grow in almost any aspect or under any conditions. However, most gardens will want to grow a fairly broad range of plants and with this in mind it is worth taking some trouble to plan and site a garden. Building entails some heavy labour so it is important to get it right the first time round.
There are three basic requirements that need to be satisfied if a rock garden is to be successful. There must be adequate drainage. Although a large number of alpines and other rock plants need a plentiful supply of water, the water must never be stagnant. A suitable site must, therefore be one where if drainage is not already good, it can be improved artificially. The position should be sheltered from cutting winds. In the larger garden it may be possible to provide a certain degree of shelter by planting shrubs at the edge of a rock garden, where walls and fences can channel fiercely turbulent cold air. A third requirement is that the position should be relatively open and free from overhanging branches.
Dripping from overhead foliage is a more serious problem than light shade. An ideal position is a gentle south-facing slope linking two levels in the garden. However, a natural slope is by no means essential and rock can be used on a level site to build up terraces with a predominantly south-facing aspect. Cost may provide a major factor limiting the amount of rock you are able to use. One of your first steps should be to visit a quarry or nursery where you can buy suitable rock. Try to use a local stone if possible, it will be more in keeping with the surroundings. If you have not already had experience of building a rock garden it is difficult to visualize the amount of rock needed for given site. The advice of a reliable firm will be of great value. A large part of the cost will be incurred in transporting the rock so look for a supply close by.
When building a natural looking feature, resist the temptation to supplement rock with man-made materials, even if you have for instance a ready supply of old bricks. If you cannot afford as much rock as you need, consider constructing a raised bed. In a more formal feature of this kind, man-made materials do not look out of place. Two other considerations should be borne in mind. You should consider how the rock garden will appear from various angles, particularly from the house. Finally, you should take into account ease of access during construction.
