Lavender is as popular today as it was in the 5th century when the Romans would scent their bath water with it. The name comes from 'lavare' meaning 'to wash'. The Abbess Hildegard of Bingen extolled its virtues in the early 12th century yet it was also in use as a herb. Lavender was dedicated to Hecate, the goddess of witches.
Lavender has been put to many uses over the centuries. It has been used as a nerve tonic, a cosmetic, perfume, strewing herb, as flavouring, massage oil and craft item. It is used to treat headaches, insect bites, eczema, chest congestion and swooning.
Today lavender is more likely to be seen as an attractive plant which will beautify rockeries, borders and cottage gardens.
Lavenders belong to the mint family Labiatae. It is a woody shrub which occurs naturally from India through the Middle East to the Mediterranean. It is now found throughout the world. There are about 25 species with a myriad of hybrids and cultivars. All are scented with white, pink or mauve flowers. The different varieties vary in habit, cultivation requirements and craft or culinary uses.
One way to make sense of all the varieties is to divide them into groups. Each group will probably have a different 'common name' according to the hemisphere they're in.
The so-called French lavender (Lavandula dentata) isn't suitable for drying or cooking but are ideal when used fresh in posies. L.dentata var. candicans has plump mauve heads and grey leaves. It is a winter-flowering variety. The smaller growing nominate plant has bright green foliage.
The second group is L. stoechas or Spanish lavender. These are early flowering, compact shrubs with plump flower spikes. Each spike is topped with prominent 'butterfly wing' bracts. Like the previous groups, these are not suitable for cooking or drying.
The English lavender (L. angustifolia) has a number of cultivars and hybrids. They have compact growth and slender flower heads. Most of these are non-camphoric (it is this factor which makes them unsuitable for cooking) so are suitable for drying and cooking. The L.intermedia hybrids are similar but later-flowering. However they contain camphor so are inedible.
The last group are ideal for posies but unsuitable for cooking. The Pteroshoechas group has fern-type leaves producing a flush of flowers in winter and sporadic blooms at other times. The foliage is musky and the plants have a more open growth than the other types. L. canariensis, L.pinnata and L.multifida are some of the varieties in this group.
The lavender is a tolerant plant and is more likely to be killed by kindness than by neglect. For best results they like full sun and excellent drainage. To prevent root rot, the beds can be raised. Add an improver to clay soils. In subtropical areas, it is a good idea to make a deep hole and half fill it with coarse gravel. Lavender likes alkaline soil with a pH preferably of 7-7.5. A handful of agricultural lime sprinkled round each plant in autumn will help lavender cope with acid soils. Give each plant a teaspoon of slow-release fertiliser each spring. Keep the plants free of weeds and prune regularly. Plant them in an open, airy position, especially in subtropical climates. Dense planting (as in a cottage garden) in areas of high humidity will result in an increase of fungal diseases.
Avoid overhead watering and over-feeding. The latter will result in soft growth and very few flowers. And if you're hoping to harvest your lavender for the extraction of oil, don't plant them close to other oil-producing plants such as eucalypts as this can interfere with the quality of the oil.
In The Garden
Most lavenders are water-wise plants, needing irrigation only while they're becoming established. They will thrive among drip-watered roses but overhead watering will encourage fungal disease. To keep the humidity down, plant near the tops of slopes or in raised beds. The scent will enhance an area along a path of under a window. Their grey foliage can provide a welcome contrast in mixed borders. Mixed groupings of tall and short lavenders with the tallest at the back will also look good.
The compact varieties can be plant in pots or tubs with a quality, well-drained potting mix. Clip them regularly to keep them shaped.
Use only English varieties for drying and cooking. Look for easily stripped leaves with no bracts at the top. When a flower head is crushed between the fingers there should be no smell of camphor. Pick English lavender and place in an empty vase to dry or you can hang it in bunches in a dry, airy place out of the direct sunlight.
The oils can give you a headache if you're stripping lots of flowers so make sure there is plenty of ventilation. It is a good idea to wear rubber gloves and a face mask. Once dried, the lavender can be stored in sealed containers in a cool, dry, dark cupboard.
When picking lavender for posies, place them straight into water to prevent them from wilting.
The key to successful lavender growing is in the pruning. They should be pruned hard but at the right time. The winter-flowering French lavenders should be pruned in summer and summer-flowering English and stoechas lavenders can be pruned in autumn. Prune every year. Pinch out the tips of the tiny plants to encourage a bushy growth. Older shrubs can be cut back a half to two thirds. Don't go back to bare wood however. Look for a spot where two or three pairs of green leaves emerge and cut back to these.
The fern-leaf group can be tip-pruned throughout the year. This will stop them becoming woody. If plants seem affected by frost, don't throw them out and don't prune them. The burnt stems will prevent the lower branches from further damage and often the plants will resprout from the base in spring. Once they do, then the frost-affected parts can be pruned out.
In subtropical regions where the growing season is longer, prune French and stoechas lavenders three times a year. As each flush of flowers begins to dry, cut back the bushes by one third. English lavenders can be cut back by a third too but only once a year in early autumn.
Unfortunately the vigour and adaptability of the lavender has the potential to make it a pest and in most parts of Victoria, Australia, stoechas lavenders are a noxious weed. South Austrlia and Tasmania also have their share of 'escaped' stoechas lavenders. The fern-leaf group is also potentially invasive in subtropical climates. It is therefore best to avoid the problem varieties.