Plants For Roof Gardens
It must be borne in mind that the amount of soil from which the plants obtain water and nutrients is essentially limited in a roof garden and the choice of plants is limited accordingly. Nevertheless, there still exist a large number of plant species and their cultivars which can be successfully grown in such conditions. First of all, there are various bulbous and tuberous plants, perennials, rock garden plants, decorative grasses and deciduous as well as evergreen woody plants, including several conifers. Always remember, however that the plants in a roof garden are permanently exposed to extreme conditions -- sunscorch, wind and frost -- and protection will have to be provided for them.
The basic element of each garden -- a stretch of lawn, be it even the smallest one -- should never be omitted. For this purpose, a layer of soil some 15cm thick will suffice.
The best method of founding a nice 'lawn' in a roof garden is by turfing. Strips of turf must be clean and weedless and be positioned close to each other on a 10cm layer of soil. Cracks between the individual strips should then be filled with a loose garden soil and the lawn lightly treaded down.
Lawns look nice framed with paving stones or concrete, or ceramic slabs arranged in various patterns. Also, large wooden offcuts of varying size can be used. They should be about 15cm high, and well impregnated with a wood preservative before being positioned close to each other. Not only paths, but also larger areas intended for sitting-out places can be paved in this way.
Small patches of lawn can be brightened, particularly in spring, by a number of small bulbs. These are planted in the autumn to make small informal groups. The possible choice covers all garden and botanical crocuses, snowdrops, snowflakes, scillas, grape hyacinths and puschkinias; also narcissi, hyacinths and tulips, including early botanical species.
Nowadays, it is often recommended that you substitute for the lawn carpeting perennials whose aesthetic function is identical to that of the lawn.
A nice heath garden can also be created on a roof. What you need for this particular type of garden is a special soil mixture composed of compost, leaf mould, peat and river sand, with an admixture of bone meal and perlite. To provide good drainage, an adequate bottom layer of coarse sand must be used.
A heath garden should include not only heaths, heathers and related plants, but also conifers and other woody plants. Attention should also be paid to decorative grasses which, if chosen with taste, will enhance and underline the beauty of this section of the roof garden. Also, some rock garden plants are good choices for a heath garden.
A 25 cm layer of good garden soil should be sufficient for most species of low-growing, cushion-forming or creeping plants intended to provide the necessary green or multicoloured patches in the roof garden. It stands to reason that even in such special conditions you should always pay heed to the resultant colour combinations, not only of flowers but also of foliage. Remember that a lesser number of species planted in larger groups makes a better effect.
Labels: Photographs of Roof Gardens