You can wait a few weeks after the flower buds open to enjoy them in your garden, but by the time you trim them, the oils won’t be as strong. If you’re using the lavender to make essential oil, it’s better to trim them early.
Avoid using craft scissors to trim lavender. They don’t make a clean enough cut. Bypass pruners are your best option. These are spring-loaded with two curved blades.
If your shrub is on the older side, you’ll likely have to cut more than one bunch. Don’t cut into the woody part of the shrub. Make sure to leave all of the wood intact, since cutting it could injure the plant.
Taking the time to do this will also help to prevent more of the shrub from turning to wood. The parts of the plant that turn to wood won’t produce new lavender stalks; the stalks grow from new shoots that emerge from the shrub every year. A big, woody base is prone to cracking or rotting, so the idea is to keep it from getting too woody.
To hang your lavender to dry, use a rubber band to tie the stems together. Hang the lavender bunch upside-down in a cool, dry spot. Allow it to dry for a week or two. Drying lavender this way preserves its color and scent. To dry your lavender in the sun, lay it flat on a screen, and set the screen in a sunny spot. The lavender will dry over the course of 5 days or so. Lavender dried in the sun tends to fade to a lighter color.
