Opal basil has purple leaves and a longer shelf life than sweet basil, but the two can be used interchangeably in most recipes. Mexican oregano has a mintier taste than ordinary oregano. If you can't find it fresh, dried oregano is a good substitute. Use curly parsley if you want looks and Italian parsley if you want flavor. Parsley doesn't hold up well to cooking, so add it to cooked dishes at the very last minute.
Frozen parsley is a good substitute for fresh, but dried parsley adds only color.
The Italians are particularly fond of this pungent herb with its needle-like leaves. They often use it to flavor meats and tomato sauces. Rosemary stems, stripped of their leaves, can also be used as skewers for kabobs. Dried rosemary is an excellent substitute for fresh. Sage is often combined with other strong herbs to flavor meat dishes and poultry stuffings.