When to cut lavender depends a little bit on what you're going to use it for -- fresh bunches, dried bunches or dried "flowers" for sachets.

Here's the progression that you'll see on a lavender stem: a lavender flower has two parts -- the base, called the calyx, and the corolla. The calyxes color up first, then one or two corollas bloom, then the first corollas start to shrivel up as the remaining corollas appear, then the first corollas start to fall off, until finally you're left with rather dull-looking calyxes containing the developing seeds. At the bottom, there's a link to a discussion at the Goodwin Creek site that has a useful diagram of a lavender stem and the parts of the flowers.

If you're going for dried bunches, you can start picking as soon as the calyxes are fat and fully colored, but it's hard to tell just when that happens (that is -- will they get a little bigger and richer in color if I leave them until tomorrow?), so I wait until the first corolla appears on the stem. Whether the calyx is a light blue or deep purple, the corollas are usually a reddish-purple ("violet" is the word Goodwin Creek uses), so they stand out, and you can walk down a row of plants that are about to bloom and you'll be stopped by something, and you'll realize it's the tiny dot of contrasting color of that first corolla on a plant.

Cut at the base of the stem, taking a pair or two of leaves. If the bush is a few years old, you can easily tell the new, green part of the stem from the old, woody part. Leave just a bit of the new growth.

For fresh bunches, it's ok -- even preferable -- if there are several flowers open on a stem, as long as none of the corollas have shriveled (if they have, you can remove them, but it's usually more work than it's worth). Customers for fresh lavender seem to like the fuller look that comes with more flowers open.

For sachets, where you'll rub the dried calyxes off the stem, you can start harvesting as soon as the first corolla appears and continue even when they start to shrivel, because the looks of the flowers aren't important. You still harvest low on the stem because the bare stalk would die anyway and have to be trimmed off the plant.

Here is a link that might be useful: Goodwin Creek -- anatomy of lavender

Thank you neil, There's a lot of information there. that's exactly what I need.

Neil, That was very helpful all the way around. Nice! You answered some of the questions I had swimming around in my head too! Thanks!
Tracy

Neil,
Thanks very much, I have just started harvesting for dried. I have a few of the corollas in bloom. I just want dried stems of lavender so I have sorted them by stem length and hung upside down in bunches. Is that the time of harvest that I'll get the best fragrance and color?
Thanks,
Cheryl

Yes, it is, for all practical purposes. The fragrance will not decline until almost all the flowers have bloomed, but as far as I can tell, it doesn't increase by any appreciable amount once blooming has started. (Some of the fragrance is in the stems, by the way. When we harvest long-stemmed lavender for sachets, we strip the calyxes from the dried stems and then bundle the stems as "lavender logs." If you roll a bundle between your palms, you get a strong lavender scent.)

I think that the color of the calyxes does decline just a bit as corollas shrivel and drop off. If you harvest a stem where there are just a few corollas left to bloom, the calyxes on the spent flowers will look a little duller than the blooming or yet-to-bloom ones.

Thanks for your help.
Cheryl