WHEN to HARVEST
Lavender should be harvested in the mid-late morning when dew has dried off the leaves and flowers but before the hot sun can wilt the stems and evaporate the oil. Don't harvest in the rain.
Lavender can be harvested with different timing, depending on its intended end use:
For dried lavender bunches, harvest when the flower heads are swollen and just one or two of the heads have started to open.
For dried lavender buds, harvest when about 50% of the flowers are opened.
For fresh bundles, harvest when 20-50% of the flowers are opened.
If harvesting for lavender oil, wait until about the half of the blooms have started to wither.
HOW to HARVEST
Grab a handful of about 100 stems and gather into a bunch. Using a small curved knife or hand sickle made for lavender harvesting, cut the base of the stems. Tie an elastic around the stems and cut another bunch.
Lavender needs to be dried in a dark, dry, well-ventilated dust-free area. If dried in the light, the color fades and if dried in too humid temperatures, mold may develop.
Hang your gathered bunches upside down when drying. Check for dryness and mold every few days. In the heat of the summer, it can take a week or two for your lavender to dry properly.
An essential part of growing lavender is annual pruning. Plants should be pruned after harvesting but just before the last frost of the season.
Using a gas trimmer, give it a hard pruning by cutting the plant back to 1-2" of green beyond its woody stem, trying to leave 2-3 nodes of the current season's wood. As you are pruning, shape the plant into a mound.
Pruning is essential as unpruned lavender tends to get overly large and splay in the center, becoming unruly and unproductive. It is also harder for unpruned plants to survive harsh winters.