While they’re still fresh:
1. Rinse. Immerse herbs in cool water, shaking gently to dislodge any soil or insects. Discard decayed stalks and leaves. Snip off stems just above a break or a bruise. Gently shake excess water from leaves (don't use a lettuce spinner; it bruises leaves).
2. Contain. Place stems in a container of water (a vase or canning jar) that holds them snugly, leaves above the rim.
3. Cover. Top leaves loosely with a plastic bag, such as a produce bag.
4. Refrigerate. Change water when it looks murky. Snip off any parts of stems that show signs of decay. If you're storing several jars, group them on a close-fitting rimmed tray to protect them from being knocked over.
Three different choices to make them last:
1. Dry. For large-leafed herbs such as basil, rosemary, and sage, snip off leafy stems, tie the cut ends together with twine, and hang the bundle upside down in a warm, dry place (away from direct sun) with good air circulation. The herbs should be dry and crisp after about two weeks. Strip leaves off stems and store the leaves in an airtight container. For fine-leafed herbs such as oregano and thyme, remove foliage from stems and spread the leaves on a clean window screen set in a warm, dry, airy place away from direct sun. Stir them every few days; once they feel crisp, store in an airtight container.
2. Freeze. Whether basil, cilantro, or parsley is your thing, freeze some for later in one of these airtight, BPA-free baby-food containers and have the taste of summer’s freshest pesto year round. Make pesto as you normally do, and then scrape the pesto into containers (fill them full so the pesto won’t darken) and freeze up to 3 months. Thaw overnight in the fridge, or put a container in a bowl of warm water to thaw if you’re in a hurry.
3. Salt. Great herbs for salt preservation include parsley, cilantro, basil, and chervil. Wash and dry 8 ounces of herbs. Pluck the leaves from the stems and roughly chop the leaves by hand. Place the herbs into a bowl and add 6 ounces of coarse sea salt. Toss until well combined. Transfer the mixture into a 1-quart jar, seal tightly, and place it in the fridge. Give it a good shake every day for one week. In a week, it should have reduced in volume by ½. Transfer your herb salt to a 1-pint jar and seal it tightly again. It will keep indefinitely in the fridge.