Well, over the years I have done some reading and some experimenting and, hopefully, have managed to learn a thing or two about drying herbs. With any luck you won't have to, and haven't yet wasted quite as many plants as I did.
- Always know what you are going to dry. Some herbs have a higher water content and will be more prone to molding if you're not careful. Some herbs involve drying the flowers, some the leaves, some the roots, some the seeds. So also make sure you know which part of the plant you're looking for.
- Timing is everything. Always cut your herbs from the plant midmorning. You want the dew to be dried up, but you don't want it to be too late in the day or the plants will wilt slightly from the afternoon heat and your herbs won't be as good as they could have been. If you're looking for leaves then cut right before the plant flowers, because that's when the leaves and stems will have the most oil in them. If you wants flowers obviously the flowers should be well established, but not wilting yet. Looking for seeds? Then the flowers should be wilting already. If you want roots then it should be late in the season when the roots will be well established already.
- Have a place ready. This was my first attempt gone wrong. I got all of my herbs cut, turned around, and said to myself, "What do I do with them now?" If you have a premade drying room then you can place them on racks inside. I have heard of people using a sauna for this, but it would have to be a dry sauna or everything would end up moulding. It is not a good idea to use a storage shed or other outbuilding unless they are airtight and you can guarantee humidity and temperature levels. Alternatively, you can dry them in the oven at about 200F or 100C making sure to turn frequently. If you don't want to risk baking them (1st attempt) then you can place 2-4 branches tied together upsidedown in a paper bag with holes in it and hang the stems/bag from your closet. The area needs to be dark and dry. Make sure that they're not packed in too tightly or you won't get good air movement and everything will mould.
- Patience is a virtue. If you're drying them in paper bags in a closet or attic then it should take about 1-3 weeks. I don't have a drying room, but would assume that it would take less time, due to the higher temperatures. I never figured out how long it should be in the oven, because I was a little oven-shy after roasting (burning) my first batch of herbs. You should test them every now and then by picking off one leaf or flower and rubbing it in between your thumb and forefinger. If it rolls they're not done yet. If it reduces itself to ashy powder instantly they're over done. The leaves and flowers should crumble slightly when squished, but they should retain roughly the smell and look of when they were growing.
- Pack it up. It's important when storing dried herbs to find an airtight container to place them in. Your best bet is to store them whole and pick off/crush a few leaves, flowers, or seeds when you're ready to use. It is possible to crush the leaves or flowers ahead of time and store them that way, but they lose their potency sooner. It is not a good idea to crush the seeds until the day they'll be used, but that shouldn't be a problem for storage, because the seeds are fairly small anyway. Do not store them in direct sunlight as it will cause them to lose their potency much, much faster. Discard your dried herbs when they begin to lose their colour or smell. Most properly dried/stored herbs will last about one year if not pre-crushed.
So, there is my spiel on drying herbs. Good luck in your various culinary pursuits in the future. I hope that this information is helpful, though I won't hold it against you if it's just not your cup of tea.
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