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Growing lavender
Lavenders are widely used in the garden and are particularly useful for edging and as low-growing informal hedges.
Cultivation
Lavenders do best in moderately fertile, well-drained, alkaline soils in full sun. Once established they thrive on poor, dry, stony soils, but do not tolerate waterlogging.
In poorly-drained soils plant on a mound or, in the case of hedging, on a ridge which will keep the base of the plants out of saturated soil. On heavier soils consider adding large quantities of gravel to improve drainage. Lavandula stoechas (French lavender) and Lavandula x intermedia will grow in slightly acid soils.
Cultivars of L. angustifolia and L. x intermedia are the hardiest. In colder areas, less-hardy species such as L. stoechas and L. dentata should be grown in a sheltered, well-drained, sunny spot or in containers that can be overwintered under cover.
Adequate spacing is essential to provide good air circulation. For informal plantings allow up to 90cm. Where grown as a hedge, plant about 30cm apart or 45cm apart for taller cultivars.
Plant in April or May and prune back to encourage bushy growth. Although lavenders are drought-tolerant, they need watering until established. Avoid high-nitrogen fertilisers. Established plants do not usually transplant; it is better to replace or take cuttings.
Containers
Lavenders grow well in containers but are deep rooted and need large pots with a diameter of 30–40cm. Use a loam-based compost such as John Innes No. 3 with added coarse grit for good drainage and a controlled-release fertiliser. Container-grown plants need regular watering in summer, but should be kept on the dry side over winter. All lavenders can be grown in containers, but container growing particularly suits the more tender ones such as L. canariensis and L. pinnata that need to be brought under cover in the winter, and the smaller L. angustifolia cultivars.
Pruning
Lavenders should be pruned every year to keep them compact. On established plants use secateurs to remove flower stalks and about 2.5cm (1in) of the current year’s growth, making sure that some green growth remains. At Wisley, pruning is undertaken in late summer after flowering, although spring pruning is recommended by some. L. x intermedia and the less hardy L. stoechas can be pruned after the first flush of flowers. Lavender does not break readily from old wood and neglected specimens are best replaced.
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