Plants for Roof Gardens and Roof Gardening
Plants for Roof Gardens with Lots of Sun
You can spend much time roof gardening and with collections of both permanent plants and temporary bedding plants for roof gardens, you can have splashes of colour and interest the whole year round. So, if conditions are suitable, these plants can enhance any balcony or rooftop garden to your benefit.
There are numerous permanent plants like shrubs and small bushes that can be grown in containers and that love hot, sunny conditions. The Rock rose (Cistus) is one that loves both conditions; it is a small, evergreen bushy plant and it produces an abundance of single rose-like blooms in pink or white throughout the summer. Many of this species have particularly pleasant aromatic foliage, and the fragrance is usually brought out by hot sunshine. The Rock rose is only suited to mild climates however, but will tolerate a minimum temperatures of -5°C ( 23°F).
Lavenders can be grown with these two plants for good colour and texture contrast. They have greyish-green, fragrant evergreen foliage with blue flowers in the summer.
Another greyish-leaved evergreen shrub which is worth growing alongside other plants, although only in milder climates, is Senecio laxifolius. The slightly oval shaped leaves are silvery-grey and covered with white fur on the underneath of their leaves. Summer will encourage their bright yellow daisy flowers; however some people dislike these and cut them off before they even develop.
Some of the smaller olearias or daisy bushes are perfect for rooftop gardens and balconies, but are best suited to mild climates. The evergreen 0learia x stellulata has a rather sprawling and straggly habit, producing heads of white daisy flowers in late spring to early summer.
Escallonias – another great mild-climate evergreen shrub, with a marvellous show of ping, red or white flowers in early summer. The smaller-growing hybrids and cultivars are suitable for rooftop containers.
Dwarf conifers would be ideal for suntraps – balconies and rooftop gardens. Given that the atmosphere is fresh and not polluted, dwarf pines would also thrive. Try Pinus sylvestris ‘Beuvronensis’, which is extremely hardy and will make a dome-shaped specimen. Equally hardy is the mountain pine (Pinus mugo) and its cultivars, which have very dense dark green foliage. All pines are evergreen.
There are many sun-adoring alpines and dwarf perennials such as all varieties of sedums; houseleeks (Sempervivum); the red valerian (Centranthus ruber), with heads of small white, pink or red blooms over a lengthy period throughout the summer and autumn. In addition to many small grey or silver-leaved plants like Anthemis cupaniana, which has white daisy flowers in summer; Artemisia schmidtiana ‘Nana’, which forms a neat mound of feathery silver-grey foliage; and for mild areas Convolvulus cneorum, with silky, silvery foliage and white, saucer-shaped flowers throughout the summer and the curry plant (Helichrysum angustifolium) with narrow and intensely silvery leaves and yellow flowers.
Plants for Roof Gardens that are Windy
Plants for roof gardens that are particularly windy, would certainly include all small hardy evergreens – these can be thoroughly recommended, but some bigger shrubs and bushes may be required to add height, such as:
BAMBOO (Arundinaria japonica) — Although this bamboo is only moderately hardy, it can take any amount of wind thrown at it. The wind easily passes through the central clump of olive green canes, whilst rustling the long, dark evergreen leaves.
If you want colour in the summer also, choose one of the purple-leaved cultivars.
SILVERBERRY (Elaeagnus commutata) —This is an extremely hardy shrub which has intensely silver foliage and, in late spring has fragrant white flowers.
KERRIA JAPONICA ‘VARIEGATA’ – This shrub will give colour and interest in spring and throughout the whole of the summer The deciduous foliage is a variegated creamy-white colour, and it produces yellow flowers in the spring. It looks great with spring-planted around its base, such as blue grape hyacinths (muscari).
You may be under the impression that that some of the taller ornamental grasses are simply not suitable plants for roof gardens that have windy positions, but in fact they are particularly wind resistant as the wind filters easily through their stems so that they neither fall over nor flatten. All of the following grasses grow exceptonally well with shrubs, providing a dramatic contrast in leaf shape, colour and texture too.
ZEBRA GRASS (Miscanthus sinensis ‘Zebrinus’) — This plant grows to about 1.2m (4ft) in height, somewhat lower than the species that can reach about 1.8m (6ft). It is a very hardy grass and the arching leaves of the cultivar are banded with yellow.
GARDENER’S GARTERS (Phalaris arundinacea ‘Picta’) — One way to control this grass is to grow it in a container as it tends to spread vigorously when grown in the garden. It is, however, one of the most beautiful of the ornamental grasses, with its white and green striped foliage that rustles in the wind. It reaches 0.6m (2ft) in height and is extremely hardy.
FEATHER GRASS, OR NEEDLEGRASS (Stipa gigantea) — This plant is not particularly hardy and is therefore only recommended for areas where the minimum temperatures are not less than —12°C (10°F). It can grow up to a height of about 1.8m (6ft). The almost evergreen foliage is greyish-green and in summer it produces bold, silvery purple plumes of flowers.