The soil needs to be on the acidic side. This is neutral 7.7 and below, to improve the soil add sulphur, a fertiliser, any humus rich matter, peat, although the latter not accepted as ethical anymore. Above the 7.7 mark would be alkaline (lime, chalk based medium). Most plants can tolerate a mixed medium and cope with the conditions but some are on the picky side. An indication of such a deficiency would be the yellowing of leaves.
Calluna vulgaris (the commonest of heathers found on hillsides, moorlands) prefers a sunny aspect but can cope with partial shade. It can flower in summer and autumn. The soil needs to be slightly on the moist side for it to do well. As long as the soil is acidic.
Erica carnea – these are winter flowering heathers. Again, an evergreen but provides you with colour where there is none. No maintenance other than taking away spent growth. These are usually dwarf varieties in an assortment of reds, pinks, whites and purples.
Azaleas are evergreen / decidious but will provide a huge of colour late spring to early summer and some are scented. Azalea ‘arborescens’ is scented but it loses its leaves.
Rhododendrons are evergreen and unlike Azaleas don’t usually cope well in full sun. They do prefer a little shade. This plant prefers a slighly cooler atmosphere. These can be used as a hedge although usually a specimen shrub. Rhododendrons have a tendency to become leggy inside if they are left unpruned for a long period. The size, shape and vigour can be retained if they are pruned each year. There are hybrids that are sun tolerant and flower later like ‘Nova Zembia’ which can continue into summer. As a rule, not scented but later flowering hybrids can be. R. burnacum, R. megacaly x. These varieties seem to flower for a shorter period and are more tender to the cold. They are a hardy and robust choice in the main.
Camellia japonica is a spring flowering evergreen. It does prefer a sheltered spot to perform well with some shade. Camellia’s do tend to be damaged by the wind and cold. Camellia’s can be moved although there is speculation they prefer not to be. However, if the plant is not performing well, to move it would be a lesser of two evils. Be mindful to do this at the right time of year. (a) dormancy period (b) try and retain as big as root ball as you can (c) avoid it drying out by soaking – can reduce the shock but not sitting in it (d) choose a well drained location with shelter and use ericaceous compost.
C. sasanqua prefers similar conditions, smaller in size, and suited to a container where it can be moved. This autumn flowering variety is more frost tender and does need additional protection. The flowers are scented too.
Pieris is an compact evergreen. It does flower in spring but is more well known for varying foliage. ‘Forest flame’ a popular specimen provides a wonderful colour from Febuary onwards and once in situ, little is needed. A larger shrub compared to this is Pieris japonica. The only maintenance, just to remove flowers or any unwanted growth. P. japonica ‘compacta’ provides white flowers but these are scented too.
Kalmia latifolia (Calico bush) This flowers in spring. It won’t compete with space since its slow growing. The amount of sun is important since the flowers will be dependent on this. Full sun ideally, not particularly drought tolerant so the soil needs to be moist or the plant partially shaded.