You can safely harvest rosemary up to 5 times every season. Check the leaves, if, when using the slightest pressure, the come right off the stem, you've waited too long to harvest. It's more trial and error than an exact science, as there are many variables in every place that Rosemary is grown. If you look at all the reasearch and thrive to adhere to everybody's guessimate when to harvest, your plant will be a tree, and partially dead. -Birdy