Lavenders are summer flowering, perennial shrubs with many small, fragrant flowers that are clustered in spikes. It is within these aromatic heads that the essential oil is contained and the extraction method is by steam distillation.
When growing for commercial purposes it is essential that the correct cultivars are planted and there are books that are recommended reading on this subject. Lavandula angustifolia varieties are best for aromatherapy andculinary purposes while Lavandula x Intermedia (or Lavandins) are used for aromatherapy and widely used in soaps and cosmetic products. Most commercial lavender plantations are established to produce essential oil, while others also combine this with the production of dried rubbings and flower heads.
Lavenders prefer a well drained soil that has full sun for most of the day. It prefers slightly alkaline soils, so lime should be applied well before planting. Although lavender is generally thought of as a drought-tolerant plant once established, drought stress can affect the performance of established crops, greatly reducing the flower head yield. In particular, the flower heads are susceptible to damage from hot, dry, salty winds.
Lavender is very tolerant of cold winters providing that the soil remains free-draining.
West coast growers have grass growing between their lavender rows to take up the moisture, while East coast growers find they can retain sufficient moisture in the soil by keeping the inter-rows weed free.
Good weed control is important to maximise the productivity and longevity of the lavender crop. To minimise oil contamination, the crop must be weed-free at harvesting time.
The expense and labour involved in weed control is frequently underestimated and crop yields can suffer badly. Some small growers have planted into weed mat and it has proven to be an excellent option for weed control and although it is expensive initially it pays for itself in the long term.
Weed mat will also protect the roots of the young plants from rabbits who will otherwise have a field day after the planting out.
If you are growing organically and not using weed mat, then a regular regime of hand-weeding and hoeing is required. Mulching of the rows is also an option as a means of weed-suppression. For non-organic production there are various herbicides that will give good weed control.