In the past my storage method for herbs was based on trial and error. Then I was given Harold McGee’s, ‘Food & Cooking – an encyclopaedia of kitchen science…
Most packs of herbs say to store in the refrigerator. But parsley on its own, and basil in a bag will deteriorate, while coriander stays fresh on its own and particularly in a bag. McGee says that ethylene is produced from the wound of the cut stems and promotes ripening and deterioration. The trick is to take the herbs from their packaging rinse and dry as far as possible. Then, as McGee says, store in loose plastic with the herbs first wrapped in tissue or a cloth to absorb moisture (and prevent microbes forming on wet leaves).
I have adopted McGee’s recommendation – but without the cloth or tissue. Stems of parsley, chervil and coriander are put in a glass or cup of water, covered in a loose plastic bag and then placed on a shelf in the fridge. Chives, thyme, tarragon, dill, oregano, rosemary and bay all keep well in bags without water stored in a tray at the bottom of the fridge. Nordic cooks might have a much larger quantity of dill – and this could get the glass of water treatment as for parsley. These methods will ensure herbs will store very well for a week or more. Rinse again after taking from the fridge.
The exception to refrigeration is basil. Coming from warm climes it quickly wilts in the cold. Basil will keep in its bag for a few days on the kitchen counter. But it may last a week or more if the stems are placed in a glass of water and placed on a warm window sill – out of direct sunlight. This treatment is less successful in winter as the sill may feel like a fridge to the basil. If there is a glut of basil, or it looks to be on its last legs, make an amount of pesto, which stores perfectly in the freezer.
Useful dried herbs include oregano, chives, tarragon and fine herbs – thyme is pointless when dried – it tastes of stale fragrant dust. I use fresh herbs as I buy them so I have not explored other methods of storing such as preserving in oil, drying. I have, however, tried freezing parsley and coriander – although the leaves go dark and will be soggy on defrosting they seems to retain their flavour. Use frozen herbs in cooking rather than a garnish.
Herbs will always be better fresh – so try to find a source of affordable fresh herbs and store as described above.