What are the hardest herbs to grow?

What are the hardest herbs to grow? In my opinion, dill is the hardest. My garden is overrun with oregano, mint, rosemary, sage, marjoram. Even the basil, parsley and chives do well if suitably located so that they don’t bolt. But dill has been a magnet for slugs, caterpillars and other insects who enjoy the taste as much as we do. I don't think I will bother with it again.

French Tarragon is another challenge but I have been more successful with it lately. Gardening guides say “Like all Artemisias, French Tarragon likes life on the dry side with plenty of sun” or “it likes a hot, sunny spot, without excessive watering” and the label on a plant I bought recently says “Water Miser – grows 2-3 feet tall in full sun.”

Not in my garden. In Encino direct sun is the kiss of death. I have found shade or partial shade much more effective. I do not think they can stand hot summers – so I would advise sheltering them. I prefer it in pots so I can move it around and it does require some water, no matter what the label says about it being drought tolerant. Use mulch to protect it but do not allow it to sit in water – the roots rot. It dies back in winter and if you are lucky it will sprout new shoots in spring, but don’t count on it.

French Tarragon is Artemisia dracunculus "Sativa," a perennial with leaves that have an Anise-like flavor that numbs the tongue. They are much used in Persian and French cuisine so that mean it's essential in our house. It is not to be confused with Russian Tarragon which I also have and which grows much taller and has beautiful yellow flowers. A milder taste - suitable for pickles. I have not grown the other variant, Tagetes lucida (Mexican marigold, Mexican Tarragon), which I hear is flavorful and easier to grow.