Hello!

Lavender growth can be impacted by many factors - too much water, not enough light, too much soil fertility, not enough pruning, soil too acidic.

It sounds like you prune every year, but possibly have not pruned enough each year. After a few years, the amount of woody growth (which doesn't produce any green growth or flowers) may be building up. To try to rehab these shrubs, you can certainly prune out any dead woody sections, but don't prune out more than 1/3 of the live woody branches annually. This pruning may help stimulate new growth.

Every year, you should try to prune the green growth down to 1-3 inches above the woody parts. Don't cut into the woody sections. Lavender can be pruned in the spring and the fall. This will encourage new green growth and blooms. Make sure you aren't overwatering the lavender, as these plants like more drought like conditions. Ensure the soil continues to drain well. Additionally, don't over-fertilize these shrubs as they typically like low soil fertility. Fertilizer can cause shrubs to produce more green vegetation at the expense of flowers. Changes in soil pH can also negatively affect flower production. Lavender likes soil pH right around 7.0. You might want to test your sol pH. If soil pH gets below 7.0 (into the acidic range), you may need to add some lime to get the soil pH back up to around 7.0.

Here are a few resources that may be of assistance with any additional lavender questions. Goodluck!

https://www.uslavender.org/index.php?option=com_content&view=article&id=95:pruning-lavender&catid=24:lavender-101&Itemid=138

https://www.uslavender.org/backyard-gardening-with-lavender

https://www.lavenderconnection.com/for-the-love-of-lavender/how-to-tell-if-your-lavender-survived-the-winter?srsltid=AfmBOopv1q2SBz_Axz3Q6wzJNRN6Kl6y5qHnbRnzq8RkMYpwKX-LaBI5

https://extension.umaine.edu/gardening/2022/05/03/when-to-prune-lavender/