Many gardeners hesitate to harvest from their herbs, worried that it will slow the growth of their plants. Best for most herbs, the opposite is true. The more you harvest, the more you get. Don't be shy about using your homegrown herbs.
Once the plants are growing well in early to midsummer, harvest regularly by pinching or snipping stems and branches. Harvest no more than one-third of the plant at any one time, unless it's the end of the season and you wish to dry or freeze the entire harvest.
Here are some specific tips for commonly grown herbs:
Basil: Pinch stems back to a pair of leaves. This encourages fresh growth and dense branching. Keep an eye out for flower buds, removing them as they form to promote plenty of fresh vegetative growth.
Oregano: I use this fresh in spring and summer and I dry it for autumn and winter use. This low-growing woody shrub produces small branches up to a foot long. Clip these with a sharp pair of pruners, leaving several inches at the base of the plant to send out fresh growth.
Chives: You can start harvesting fresh chives once the leaves emerge in early spring by clipping bunches of the foliage. Once the flowers form in late spring, try to avoid snipping their stems when you harvest more leaves. The flower stems are edible, but they have a tough, woody texture. The flowers are edible, too.
Rosemary: If you only need a small amount, you can pick individual leaves. For a larger amount, cut several inches off the stem tips. But remember, remove no more than one-third of the plant.