Lavender Research Highlights: Bloom Characteristics of Cultivars

The final report of the 2013 lavender research trials is now complete. The report is comprehensive and discusses the results of four main research trials in great detail. The four research trials include cultivar trials at 6 sites across southern Ontario, row cover trials at 4 sites in southern Ontario, a plastic weed barrier trial and an oil distillation trial. Over the next few months, highlights of the results will be written in a series of articles. The detailed report will be posted to the Ontario Lavender Association website at within the next few weeks.

In this article, bloom characteristics of the 27 cultivars included in the cultivar trials will be discussed. Characteristics such as bloom height, bud spacing and flower and bud colour are important for determining whether a cultivar is suitable for different value-added products. For example, tall flower stems are more suitable for bundles, while shorter stems may still be suitable for oil distillation or other purposes. Different flower colours provide contrast in the field if the farm is open to the public, but white flowered cultivars may not be as useful for product development.

Figure 1 shows a comparison of the stem and flower height of the 27 cultivars included in the cultivar trials. The diagram is to scale and represents the data collected over six sites. The coloured oval on each stem represents the flower cluster and shows the height from the lowest whorl of buds to the top of the flower, the colour of the flower petals (outside oval) and the colour of dried buds (inside oval). Extended flower clusters generally have wide spacing between buds, which may be undesirable. The cultivars are in the approximate order of bloom period with the earliest blooming cultivars on the left. Since lavandins (Lavandula x intermedia) bloom later than angustifolias (Lavandula angustifolia), they are in the right of the diagram beginning with Edelweiss. Lavandins are clearly taller than angustifolias. The tallest flowers in the diagram, Hidcote Giant, averaged 48 cm in height across all six sites. However, some sites had taller flowers and Hidcote Giant averaged over 60 cm in height in a few locations.

July 8 2014 Figure 1
Figure 1. Scale diagram of the average stem and flower height of 27 lavender cultivars at six sites across southern Ontario. Flower (outer oval) and dried bud (inner oval) colours are indicated. For comparison, Hidcote Giant flowers were 48 cm tall from the base of the stem to the tip of the flower. A relative rating of winter hardiness over four years of research is included next to the cultivar name.

Flower height is not the most important factor in choosing a cultivar. If it doesn’t survive the winter in Ontario, a cultivar is not very useful no matter how favourable the flowers may be. Figure 1 also shows a rating of winter hardiness based on four years of research. It should be kept in mind that the winter of 2013/14 was especially harsh and all lavandin cultivars did poorly across all research sites.

Based on this research, Melissa and Edelweiss are good white/pink cultivars to provide colour contrast in display gardens. Folgate, Royal Purple and Royal Velvet are the angustifolias with the most potential for flower bundles. All lavandins are suitable for bundles but many are not as hardy in Ontario. Most angustifolia cultivars have dark purple buds that can be used for crafts, while most lavandins have green buds that are more suitable for products where the buds are hidden or where the purple colour is not necessary. Gros Bleu is the only lavandin with dark purple buds.

Growers should avoid choosing cultivars for large-scale plantings based on flower appearance alone. Flower and oil yield, oil quality, winter hardiness, plant growth and bloom period are other important factors for planning a lavender farm and were also assessed in these research trials. These will be presented in subsequent articles.

Funding for this project was provided by an OMAFRA New Directions Research Program grant to the Ontario Lavender Association (OLA). The project is a collaboration between OLA, OMAFRA and the University of Guelph.

About Sean Westerveld

Ginseng and Medicinal Herbs Specialist, OMAFRA
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