The best time to pick herbs for preserving is early in the day before the sun wilts their leaves. Pick through the leaves and stems and throw out any that are discolored, wilted, bug-eaten, or withered. Rinse the herbs in cool water, making sure to remove any dirt, debris, or bugs. Pat them dry and lay them out to dry thoroughly on paper towels.
Drying HerbsThe simplest preservation method for herbs is air-drying. Gather bunches of the herb and tie them into bundles by wrapping the stems with twine or a rubber band. Hang the bunches upside-down in a well-ventilated, warm location, away from sunlight. They will dry in 1-4 weeks, depending on the type of herb and where you are drying them. Cover them with a paper bag while they are drying if you are worried about sunlight or dust gathering on them.
A dehydrator is also an excellent way to dry herbs. Lay the leaves out in a single layer on the dehydrator trays and set the heat to low. It will take 6-8 hours for each batch. When the leaves are crumbly, remove them from the dehydrator and put them in a glass jar. Crumble the herbs into small bits or leave them as larger pieces; it's up to you.
Drying herbs in the oven is also an easy process. Set the oven to 150F. Line a baking sheet with parchment paper and spread the herb leaves out evenly. Keep the oven door propped open slightly -- a wooden spoon propping the oven door open works wonderfully. Check on the herbs often because each variety dries at a different rate. They usually will dry in 1-4 hours. When they crumble easily, they are done.
Freezing HerbsFresh herbs can be frozen by wrapping them loosely in plastic wrap and placing them in a freezer bag. Or, you can chop them up finely, pack them tightly into ice-cube trays, and cover them with water or vegetable broth. After the herbs are frozen, remove the herb ice cubes from the tray and store them in large plastic freezer bags. Frozen herbs change consistency after being thawed, and they are best used for cooking and not as a garnish.
All preserved herbs should be used within a year. The potency and aroma start to deteriorate when they are kept longer.