Timing is everything with lavender - late summer/fall is the best time to trim
- promote healthy growth
- maintain its shape
- encourage abundant flowering
- prevent woody and leggy stems that show sparse growth
Here are easy steps to prune lavender effectively:
Timing: Prune lavender soon (late summer or early fall) after its main flowering period has ended. Avoid pruning in winter or early spring, as this can potentially damage the plant during colder months. Pruning at the right time helps the plant recover and produce new growth before winter sets in.
Tools: Use a pair of sharp, clean pruning shears or scissors. It's important to use clean tools to prevent the spread of disease.
Remove Spent Flowers: Begin by removing the spent flower stems. Use your pruning shears to cut back the flower stems to just above the first set of leaves. This not only improves the appearance of the plant but also encourages new growth.
Shape the Plant: To maintain a compact and attractive shape, lightly trim the overall foliage. Trim no more than one-third of the total height of the plant. Avoid cutting into woody stems, as this can harm the plant's growth.
Avoid Over-pruning: While it's important to maintain the plant's shape, avoid over-pruning, as lavender can have difficulty regrowing from old wood. Focus on removing the top growth and shaping the outer portions of the plant.
Bonus Tip: In the spring, you can also do a light pruning to remove any dead or damaged growth that may have occurred over the winter. However, the main pruning should be done after the main flowering period in late summer or early fall.
Remember that lavender prefers well-draining soil and full sun. Regular pruning, along with proper care, will help your lavender plant thrive and produce beautiful blooms.
Another great article on trimming different kinds of lavender is here (from Monrovia).