Production Tips For Top Performers: Lavandula Stoechas

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Production Tips For Top Performers: Lavandula Stoechas

Figures 1a and b. The flowers of Spanish lavender or
L. stoechas have showy, whimsical bracts on top
of the inflorescence, reminiscent of bunny ears.

Few plants can match the romantic appeal of lavender. The silvery foliage and drifts of flowers are lovely in their own right but are also evocative of old-world charm and idyllic sun-drenched Mediterranean settings. Lavender plants are surely one of the best choices to line a sunny garden path, where brushing against them as you pass will release that classic scent. In a container garden, people can enjoy the fragrance and spiked inflorescences up close. Lavender is produced commercially for its essential oil, valued in perfumes and also has some medicinal and culinary uses. In floriculture, lavender is a desirable and popular part of both the herb and ornamental segments of the market.

Lavenders are also a very practical choice for modern gardeners since they are drought-tolerant and not attractive to deer or rabbits. There are some 40 species in the genus. Those used ornamentally are semi-woody herbs with flowers of white, pink, purple or, naturally, lavender. English lavender (Lavandula angustifolia) is probably the most commonly grown lavender but other species offer uniquely appealing characteristics.

The flowers of Spanish lavender or L. stoechas have showy, whimsical bracts on top of the inflorescence, reminiscent of bunny ears (Figures 1a and b). The fragrance is more sharp or piney than that of English lavender. Reportedly, Spanish lavender tolerates heat and humidity better than English lavender. Spanish lavender thrives in sunny dry places and is actually considered an invasive weed in parts of Australia. It is a fantastic potted flowering plant that makes an excellent addition to container gardens or borders and is hardy to Zone 8. This species is also sometimes known as French or Italian lavender.

Figure 2. Plants began flowering five to six weeks after
transplant under long days (16-hour, LD), but took more than
15 weeks to flower under short-day (nine-hour) photoperiods.
Plants were more compact and attractive under long days
provided with high-pressure sodium (HPS) lamps compared
to those grown under incandescent (Inc) lamps.

Materials and Methods

We trialed four cultivars of L. stoechas from Ball Floraplant: ‘Chica Purple,’ ‘Chica Rose,’ ‘Coco Purple’ and ‘Coco Blue and White.’ Our starting material was 128-cell vegetatively propagated plugs that had been pinched three times before arrival. Plugs were transplanted into 5 ½-inch pots and forced at 68°F under three photoperiod conditions: nine-hour short days, 16-hour long days created with incandescent lamps, or a higher light treatment of 16-hour long days created with high-pressure sodium lamps.

In the higher light treatment, plants received about 25 percent more total light per day than in the other two treatments. To provide a cold treatment, we also placed a group of plugs in a lighted cooler at 41°F.

Results

Spanish lavender does not require cold to flower. However, photoperiod did have a significant effect on flowering (Figure 2). Long days hastened flowering dramatically–under short days, plants took over 15 weeks to flower. Under long days, the first flowers opened after only five to six weeks on the more compact Chica varieties, or seven to eight weeks on the taller Coco varieties. Therefore, we would classify Spanish lavender as a facultative long-day plant.

When the first flowers opened, our Chica plants were 8 to 12 inches tall while Coco plants were 11 to 16 inches in height. In general, the growth habit of Chica varieties was more compact and tidy, and they produced more flowers than Coco varieties.

Postharvest

We were very impressed with the phenomenal shelf life of our Spanish lavender plants. They continued to produce flowers while under long days and just kept looking better and better as time went on (Figure 3). Each inflorescence remained attractive for a long time, and plants branched and rebloomed very well after pinching or pruning.

Figure 3. Spanish lavender ‘Chica Purple’ continues
to produce flowers as long as the plants are under long days.

Production Notes

Like other lavenders, it is critical to provide excellent drainage and avoid overwatering these plants. The media should be allowed to dry between waterings. Our Spanish lavender plants performed well in the greenhouse in a commercial peat-perlite media. However, the plugs we placed in a cooler at 41°F nearly all became infected with Pythium and died. If starting with unrooted cuttings, it is vital to avoid excess moisture during rooting as well.

Spanish lavender is native to sunny climates and prefers high light. Plants can become straggly under lower light conditions and will produce fewer flowers.

While the specific varieties we worked with are not currently offered, a number of other attractive cultivars have been released recently. Growers may need to adjust production schedules slightly, as time to flower may differ from the varieties we trialed. Whichever variety you try, Spanish lavender can create the feel of a sunny Mediterranean paradise, or mark the arrival of spring as a unique potted flowering plant.

Cathy Whitman is a research technician at Michigan State University. You can eMail her at whitmanc@msu.edu.

Sonali Padhye is with Ball Horticultural.

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