Use a food dryer, or your freezer to preserve herbs. Whether you grow them in your garden, raise them in containers, or buy them fresh from the grocery store, your herbs will never go to waste if you dry them or freeze them for later use
An overgrown basil planter can provide ample clippings. If you don’t use all of them in-season, try dehydrating the extra in a food dryer.
Harvest herbs to preserve as you’d harvest them to use fresh in cooking. Various authorities differ on the “best” way to harvest—harvest before the plants flower, harvest while they’re flowering… I say, harvest to keep the plants from getting out of control.
More importantly: experiment. You might prefer mature herbs while someone else prefers younger ones. What’s more, it’s not reasonable to generalize for all herbs. Once sage blossoms, for example, its flavor changes distinctively. I haven’t noticed such a change in basil.
Generally, you should harvest stems with leaves attached. Depending on how out-of-control the plants are when you harvest, you may cut off whole branches, or you might cut branches back to where two or three sets of leaves remain. Many herb plants will send out new branches below a cut as long as there are leaves on the remaining sections; basil is a classic example. Other herbs, such as cilantro, have such a short lifespan that you might prefer to harvest much of the plant for its leaves and grow other plants if you want to harvest seeds. (I harvest only the broadest cilantro leaves and leave the remainder of each plant to go to seed.)
Rinse the herbs gently to remove soil and insects. Then remove as much water as you can from the herbs. I gather the edges of a clean dish towel to form a sack with the herbs inside and shake it gently for a minute or two.
Lay branches of herbs on the trays of your food dryer. It’s OK if the branches criss-cross on the trays; air will circulate around them adequately. Don’t, however, compress the herbs by pressing them down.
If your food dryer has a temperature control knob, set it at 90 degrees Fahrenheit. The herbs may dry in as little as two or three hours, but don’t remove them from the dehydrator until the stems are brittle and snap when you bend them.
Supposedly, herbs will retain top flavor longest if you leave the leaves attached to the stems. I find this terribly inconvenient. Rather, I put the herbs in a blender—if the stems are particularly woody, I pluck and preserve only the dried leaves and discard the stems. If you’ve dried your herbs adequately, you don’t need a blender. Put them in a plastic bag and crumple it in your palm repeatedly.
I try to refill my spice jars during the growing season, and I also store ground dried herbs in zippered plastic bags. Ideally, store herbs in a cabinet or other location where they’ll receive limited or no light, and where the humidity remains low.