I know recipes often benefit from using fresh herbs, but I find buying fresh can be expensive and I do not have green fingers to grow my own. Would you say that dried herbs are as useful or should I look at frozen herbs that you can get from most supermarkets. Also I am aware that dried herbs can be stronger in flavour is there a good rule of thumb to follow when using dried against fresh? Many thanks!
When deciding if to use fresh, frozen or dried herbs it is best to consider the type of dish you are making. If the dish is cooked for good length of time, roughly 30 minutes or more, then it may be possible to substitute dried herbs for fresh. And sometimes-freeze dried herbs can be used if the cooking time is slightly less. But if the herbs are used as a finish or a garnish then you really can't substitute dried herbs for the fresh ones as the dried ones will have a different taste and texture. If using dried herbs then use 1/4 to 1/3 of the fresh herbs. Dried herbs stale over time so check the containers to find the "best before" dates.
With frozen herbs you can use them if the herb is stirred in and cooked for a few minutes. But again these herbs are not great replacements for garnishes as the frozen herbs will tend to be fairly limp when thawed, and in many cases finely chopped.
You can prolong the life of fresh herbs by storing them properly. Basil can be bought in pots and will keep on a windowsill for several weeks if watered regularly. For bunches of herbs you should store them in the door of the fridge or in the salad crisper section but make sure they are not pushed to the back of the fridge where it is colder. Once the package of herbs has been opened you can wrap any unused herbs in a damp piece of kitchen roll (paper towel) and reseal the bag with a clip or elastic band or seal them in a plastic food or freezer bag. If the herbs have been picked from their stalks, but not chopped, then put them in a resealable container and cover with a damp piece of kitchen roll before putting the lid on the container. Again store the herbs in the door or the front of the fridge. Basil and mint tend to perish most quickly.