The French use French tarragon, or estragon as it is called, in cooking frequently as it goes well with many fish and chicken dishes. It has a clean taste rather like fennel or aniseed. Unfortunately, it can be difficult to grow. Russian tarragon is more readily available and growns well but it has hardly any flavour at all so it's really not worth buying it for a herb garden. In Britain, my experience is that a tarragon plant is good to use in cooking well into November and is also good chooped and frozen with a little water to add to sauces and gravies.