Notes on Lavender and Frost

With frost potentially in the forecast this weekend, here are some thoughts on ways to protect lavender to avoid a repeat of last year.

  1. Refer to the THIS ARTICLE for a discussion of the available weather forecasts and their reliability.
  2. Keep in mind that lavender is normally unaffected by mild frosts at this stage of development. Last year, ground temperatures were close to -9oC on the ground in some areas on May 23 and bloom buds were already developing when the frost occurred.
  3. If low temperatures are forecast to be close to freezing, consider that ground temperatures can be much lower, especially if the dew point is very low (i.e. very dry air)
  4. Row covers will provide a few degrees of protection. While growers have removed row covers that provided winter protection, it may be a good to consider re-covering them if a significant freeze is in the forecast. While growers may not have the labour to cover all of their plants, they may be able to protect enough plants to keep agri-tourism activities alive for this summer should there be a similar frost to last year. Consider that covers will not need to be weighed down nearly as much if erected the evening before a frost when winds are calm than they are over the winter, which will lower the labour costs.

Hopefully the rainfall over the last few days in many areas will keep humidity up which can lessen the severity of frost events, but it is best to err on the side of caution.

Some lavender growers have noted that some shoots are not greening up yet, while the interior of the plant has longer shoots. There may have been some damage from the April cold spell when plants were already greening up. However, it is too early to say if the damage is permanent or if new shoots will emerge from the stems. Last year’s experience has shown that tops that are completely killed above the crown are best mowed off completely to allow for more vigourous growth from the crown, but it is too early to make that call.

About Sean Westerveld

Ginseng and Medicinal Herbs Specialist, OMAFRA
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