Lavender enjoys an open site in full sun and copes well in drought conditions. In wet, heavy soils they may suffer. To avoid this improve the soil before planting by digging in horticultural grit. The ideal soil type is a well-drained, neutral to alkaline soil. Lavenders are not as happy on acidic soil, apart from Lavandula stoechas.
It's sensible to grow half-hardy and tender types in containers so that they can be moved to a light, airy frost-free place in winter.
The best time to plant tender lavender is in spring. Hardy types can also be planted in autumn.
On heavy, wet soils plant on a mound to help the plant cope with the wet. Plant at the same depth as the plant was in its pot. Add a sprinkling of bonemeal to the planting hole, place the plants in the hole, backfill and firm in. Water well.
When planting in containers choose terracotta pots with drainage holes. Fill pots with a John Innes no. 2 or 3 and mix in some horticultural grit. Pots should be placed in a sunny spot away from overhanging trees and shrubs.
Semi-ripe cuttings can be taken in late summer. Remove non-flowering cutting material of about 10cm long with a woody base and a tip with new growth. Pull off some of the lower leaves. Fill plastic pots with cutting compost, water and then push the cuttings into the compost. About 1cm should be below the soil. Cover pots with a clear plastic bag and place in a light and airy place. A greenhouse is ideal.
Lavender can be become very leggy and bare few flowers. The reason for this is lack of or poor pruning. Many gardeners just deadhead hardy types which leads to leggy plants and few flowers. Looked after in this way the plant will be very short lived.
To rejuvenate a woody plant, prune in mid-August to just above a green shoot and hope for the best. If new shoots don’t appear within the next month you might be better off starting again.
Hardy lavenders (angustifolia and x intermedia types) can be left in the garden all year round. Prune plants after flowering in August. Plant will benefit from being cut back quite hard as long as there are green shoots evident below your cut. Cut into old wood and you may sacrifice flowers the following year. If you cut out all evidence of shoots it is likely you’ll finish the plant off. Hardy types can cope with temperatures down to about -15ºC.
Frost hardy types, such as Lavendula stoechas, flower for a long season. These plants survive in the garden if they’re in a sheltered spot and it’s a mild winter. Prune after their first flush of flowers have faded and avoid pruning any later than early September.
If growing the more unusual tender types, such as the Lavandula denata, deadhead and only prune as above if the plants are becoming scruffy.