Tips For Producing Lavandula
Advice from Green Leaf Plants on producing Lavandula Angustifolia, Lavandula ×intermedia and L. stoechas.
September 5, 2012
Lavandula has long been admired for its elegance in the garden and valued for its numerous aromatherapy and culinary uses. Its popularity makes lavandula one of the top 10 most searched perennials on Google! This diverse genus offers a medley of flower forms and colors from deep purple to blue-violet, pink and even white. Foliage can range from green to silver with different leaf forms and habits. Some of the most popular and commercially available species include L. angustifolia, L. ×intermedia (latifolia × angustifolia) and L. stoechas.
In the garden, lavandula prefers well-drained soil and will not tolerate long periods of wet soil. Soil pH should be 6.5 to 7.5. Pruning to 1/3 or 1/2 after flowering is recommended to rejuvenate garden plants for the following season.
For commercial production, a well-draining media is a necessity. Avoid overhead watering to prevent foliar disease. Watch for fungal diseases, especially Botrytis. Good air movement is beneficial and high-light levels are encouraged. Insects are not usually a problem but plants can be affected by aphids. A target pH of 6.0 to 7.0 and liquid feed at 100 to 150 ppm nitrogen is recommended for best growth. Maintain an EC between 0.75 to 1.2 mmhos/cm and reduce feed once the plants begin to flower. Air temperature should be between 55 and 65°F (13 to 18°C) night and 65 to 80°F (18 to 27°C) day. Most plants finish well in a 1-gallon pot.
1 Lavandula angustifolia or traditional English Lavender is typically hardy to USDA Zone 5. These can be propagated vegetatively, but there are also some quality seed genetics on the market. L. Lady and the L. Ellagance series flower first year under long days of 14 to 16 hours. Most other L. angustifolia benefit from vernalization and long days before they will bloom reliably. For those that require vernalization, a vernalized plug can be planted in spring or unvernalized plugs can be planted in late summer-fall before overwintering. A cold greenhouse set at 35°F (2°C) is recommended for overwintering outdoors. Flowering will occur late spring-early summer of the following year. For unvernalized production from a spring planting, it will take approximately 10 to 14 weeks, depending on temperature, to finish a 1-gallon pot from a 72-cell liner.
2 Lavandula ×intermedia varieties are also known as lavandin and include hardy types (USDA Hardiness Zones 5 to 8) that bloom later than L. angustifolia. ‘Grosso’ and ‘Provence’ are popular varieties in this category and famous for their longer flower stems and flower spikes. These should be produced the same way as L. angustifolia that require vernalization as described in No. 1.
3 L. stoechas is also known as French or Spanish Lavender with showy bracts on top of the flower heads. Most Lavandula stoechas varieties do not require vernalization and are only hardy to USDA Zone 7 to 8, depending on the variety. These can be planted in a warm greenhouse as early as January for spring sales using long-day lighting of 14 to 16 hours. They can also be planted in spring for May-June sales without providing additional light.
These tips were provided by Melanie Neff, technical support specialist for Green Leaf Plants. Using data collected in the trial garden in Lancaster, Pa., she and the product support team develop authoritative technical guides for many plants. These are available online at GLplants.com.