Drying Vervain for Tisane

I bought six vervain plants from you last year. They've done extremely well. Unfortunately I've mislaid the sheet that came with them, and I need to know if there are special instructions for harvesting and drying leaves for tisane. I haven't found anything on-line, but I know I have to harvest now, as the plants are getting ready to flower.

Harvesting and drying vervain (Verbena officinalis) is the same as most other aromatic tea herbs. As you suggest, the optimal time for drying is when flowering begins. This is because the aromatic oils in foliage is usually at their highest levels just as the flower buds begin to open. Like all aromatic foliage herbs, it is best to wait until the dew evaporates on a sunny morning to pick the foliage. Don't wait until the afternoon or evening otherwise the oil because the levels drop through the course of a day starting at about noon.
If you drying for personal use and you have a manageable amount of plant material, it is a good idea to strip the leaves and tops by hand from the biggest stems. That's because the stems are a reservoir of water and this water slows the drying process. The magic for getting top-quality dried herbs is to dry quickly with as little heat as possible and in the absence of direct sunlight. Stripping the leaves and tops and setting them on a sweater dryer placed in a shaded but airy place is a tried-and-true method for doing just that.