Pruning Lavender is Essential
Chris Mulder, Barn Owl Nursery
In my experience, I have found that pruning lavender plants in the spring and summer, and lightly in September, helps them to look and grow better, over a longer period of time. This has worked well for me in my location, but not everyone growing lavender in different climates in Oregon will prune their lavender plants that often.
Pruning should begin early, when lavender plants are still young. Younger plants grown in pots would have a better start if they were not allowed to flower the first year. Then all the new growth would go into the foliage, not the flowers, to produce less woody looking shrubs with more growth at the base of the plant.
The English lavender cultivars (L. angustifolia) usually require more pruning to hold their shape than the lavandins (L. x intermedia). French or Spanish lavenders (L. stoechas), require even more pruning. Tender species of lavenders usually do not survive a winter outside in Oregon, so they do not need to be pruned as often since they are only growing outside for less than a year.
In a home garden, most lavender plants will hold their shape for at least 10 years if they are pruned regularly. If the lavenders are growing in a hedge, they should be pruned twice a year. The first trim can be done in the spring, to shape the plants before they put on a lot of new growth. Cut lavender hedges along the sides more than on the top of the plants. After they finish blooming in the early summer, then trim the hedge evenly, all around. This will help to maintain the shape of the hedge, encourage new growth, and possibly produce more flowers later in the summer or early fall. This can be done while harvesting the flowers for fresh and dried bouquets.
Lavender plants that have not been pruned become woody looking sooner. If you already have old, woody lavender plants that have never been pruned, it may be too late to shape them. However, I have revived old woody plants by pruning them severely. It is possible, if the plants have new green growth just above the woody part. The branches can be pruned back heavily, to within three sets of leaves on the stems. You can prune the whole plant down to 1/3 of its size. With this heavy pruning, the plants may require fertilizer and more water to encourage new growth on the woody stems. Only try this drastic pruning in the spring. Watch for growth later in the spring. If there is no new growth within two months, then it is time to replace the old plants with new ones and get them established before summer.
In the summer, when I am harvesting the flowers to sell, I cut the flowers with as long a stem as possible so the stems have a few sets of leaves on them. At this time, I am lightly pruning the plants to encourage new growth. Some of the English lavenders will bloom again and I will have more flowers to harvest later in the season.
In general, all lavenders benefit from being pruned at least once a year. If you only have time to prune one time, then try to do the major pruning in the spring and summer months. If you do not harvest the flowers, then cut off the long stems of lavender flowers, with some of the leaves, after the flowers lose their color. Once lavender plants are established in the garden, they should be pruned well for the whole life of the plant. If you start early, and prune regularly, then you will enjoy the shape of the older lavender plants in your garden and they will produce more flowers for many years.