Gardening: Lavender pruning can make for healthier plants
The lavender has already been pruned in preparation for winter and next summer’s harvest. Shaping them into a turtle-like mound helps keep them producing quality floral stems with a uniform stem length. Pruning is simple when you use a hedge trimmer. The process involves removing much of the current year’s growth leaving only one to two nodes from which new growth will emerge. When winter injury, or spring damage, occurs, cutting back even deeper into the plant in late spring is sometimes necessary. The key, at least for commercial production is creating a uniform ball of shoots and stems.
Shaping the plant helps ensure all the floral stems are the same length making harvest easier. When floral stems develop at different depths in the shrub due to improper pruning it is difficult to obtain the same length of stems for fresh or dried bouquets. When harvesting for distillation of the essential oil (e.o.), less of the stem is taken, but even then it is nice to have the flowers at the same height on the plant. While home gardeners collect a few bundles of flowers, commercial lavender operations can harvest nine to eleven bouquets each with one hundred and fifty stems from a single plant depending on the cultivar. When you have thousands of plants needing harvest it is impractical to collect each stem individually. Grasping a hand full of stems and slicing through them with a sickle is the more practical way to harvest for field bundles. While still holding the bundle, a rubber band is wrapped around the base of the bundle to hold it together. The bundle is either hung for drying or prepared fresh for the market. Harvesting for essential oil is even easier as the shorter bundles are placed loose in a basket for distillation.
There are still times when pruning in the spring is necessary to remove any shoots extending well beyond the turtle-shaped plant. Pruning these back however results in delaying the floral stems. In addition, there are time when the floral stems on one side or portion of the plant bloom before the rest of the plant. When this occurs the floral stems ready for harvest are pulled together by the handful and removed with a hand-held sickle. Some plants may need to be visited several times before all the floral stems are collected.
The flowers on the floral stem open from the bottom to the top. When harvesting for dried bouquets the floral stems are harvested as the first flowers are opening. For fresh bouquets the floral stem should be purple all the way to the top and the top of the stem should spring back when pressed to the side. Waiting to harvest until the flowers begin to wither is too late for use as fresh bouquets as the buds drop off.
This past year I was concerned about winter injury as eleven thousand cuttings were taken from one of my fields in October. Pruning stimulates growth and if that growth does not acclimate properly for winter, more winter damage can occur. Surprisingly very little winter/spring damage resulted from the late collection of these cuttings.
Many lavender farms throughout the U.S. suffered losses last winter some of it possibly due to when the plants were pruned. Some commercial farms lost ninety-five to one hundred percent of their plants creating a shortage of US produced buds, essential oil, and bouquets. Losses even included Lavandula angustifolia, the common culinary lavender, which is reported to be quite winter hardy. Farms in the Grand Valley lucked out this past winter with few growers loosing plants. Hopefully again this winter our area will be spared the damage others have experienced.
Free Press columnist Dr. Curtis E. Swift is a retired horticulture agent with the Colorado State University Extension. Reach him at Curtis.Swift@alumni.colostate.edu, 970-778-7866 or check out his blog at http://SwiftsGardeningBlog.blogspot.com. He owns Swift Horticultural Consulting and High Altitude Lavender.
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