Lavender

Light and exposure

Lavender demands full sun, no compromise. It is a plant of the garrigue, used to light and heat; in shade it grows leggy, flowers poorly and rots easily. Give it the sunniest, warmest spot in the garden.

A position on a slope, in a rock garden or on top of a bank is ideal here: the sun warms it and water drains away instead of sitting. Against a south-facing wall it also benefits from the stored heat, which makes up a little for the coolness of our climate.

Watering

Lavender hates excess water. Once established, it is very drought-resistant and needs almost no watering: the rain in our regions is more than enough. Watering an adult lavender means risking rot.

The only time a little water is justified is the first year, after planting, while the roots settle in, and only if the summer is truly dry. In a pot, let the substrate dry well between waterings and never leave water in the saucer.

Soil and repotting

This is the decisive point in our climate. Lavender wants a poor, stony, chalky and above all perfectly drained soil. It thrives where other plants suffer from drought. What it cannot tolerate are the heavy, clay and moist soils so common in the Herve region.

To succeed in heavy soil you have to lighten it: plant on a mound or in a rock garden, work plenty of coarse sand, gravel or pozzolana into the planting soil, and raise the level so water runs off. A bed of gravel at the bottom of the planting hole helps too. Without this drainage work, lavender rarely survives more than one or two winters here.

Temperature and humidity

True lavender, Lavandula angustifolia, is the hardiest of the lavenders and takes frosts of several degrees below zero without harm. Dry cold does not frighten it, it is far more resistant than French lavender or the lavandins.

The Belgian trap is therefore not the temperature but the combination of cold plus moisture. A mild, sodden winter, which we often get around Herve, is far more fatal to it than a properly cold but dry one. Its roots rot in waterlogged soil. Everything comes down to soil and drainage: a lavender planted in free-draining soil sails through our winters with no special protection, a lavender with its feet in water dies.

Pruning and upkeep

The annual prune is essential to keep lavender compact and stop it going bare and woody at the centre. The right moment is just after flowering, at the end of summer. Cut back the spent stems and trim the foliage by a good third, always keeping some green parts: never cut into old bare wood, it will not regrow.

A light shaping prune can also be done in early spring, to tidy the clump before it starts up again. Without regular pruning, lavender ages fast, opens up at the centre and ends as a bush of dead wood barely in flower. A plant pruned well every year stays dense and lives much longer.

Pests and diseases

Lavender is little prone to disease when its conditions are respected. The main problem comes from excess moisture, which causes root rot (Phytophthora) and makes the plant die back from the base. Here again it all comes back to drainage: a lavender yellowing and browning from the bottom is almost always a lavender whose feet are too wet.

Among the few pests, the lavender leafhopper can transmit the stolbur phytoplasma, which gradually kills off plants in some regions, but this stays marginal here. Most often, an ailing lavender in a Belgian garden is simply suffering from soil that is too heavy and too wet, not from a disease.

Propagation

Lavender propagates very easily from cuttings, far more reliably than from seed. At the end of summer, take non-flowering stems of the year, about ten centimetres long, strip the lower leaves and plant these cuttings in a sandy, free-draining mix. Keep them sheltered, watered sparingly, and they will root within a few weeks.

Seed sowing is possible but slower and more unpredictable, the seeds often needing a cold period to germinate. To get plants identical to the mother plant, cuttings are better. Bring the young rooted cuttings under shelter for their first winter before planting them out in the garden the following spring.

Month-by-month care calendar

Green Hub tips

• Here, lavender dies of moisture, not cold: drainage is everything. Plant on a mound and lighten the soil with sand and gravel.
• Do not water it once established. Belgian rain is enough, and excess water is the leading cause of death.
• Prune every year just after flowering, by a good third, never cutting into old bare wood, which does not regrow.
• Take cuttings at the end of August from non-flowering stems: it is far more reliable than sowing and you get free new plants.