Why Your Herbs Give Up So Quickly

There is a particular disappointment in opening the fridge on Wednesday to find the coriander you bought at the weekend has collapsed into a slimy yellow mess. It happens to almost everyone. The good news is that it is not inevitable. A few minutes of attention when you unpack the shopping can add a week — sometimes two — to the life of a bunch of herbs.

Supermarket herbs are usually grown fast and cut young, which means they arrive with plenty of leaf but very little root to draw water from. Once cut, the leaves keep losing moisture through their surface while the stems have nothing to replace it with. Most of what we call "keeping herbs alive" is really just slowing that process down: keeping the stems drinking and the leaves dry. Get those two things right and you will throw away far less, which matters when a modest bunch can cost a pound or two.

Treat Soft Herbs Like a Bunch of Flowers

Coriander, parsley, mint, dill, chervil and tarragon all behave in roughly the same way. They are soft-stemmed and thirsty, and they do best standing upright in water. Take them out of the plastic sleeve, trim a centimetre or two off the base of the stems with a sharp knife — cutting at a slight angle gives more surface area for drinking — and stand them in a glass, jar or small jug with two or three centimetres of cold water.

From there you have a choice. If you are going to use them within two or three days, a spot on the windowsill is fine. For longer storage, cover the leaves loosely with a reusable bag or a sheet of cling film and put the whole thing in the fridge door. Change the water every day or two; cloudy water is a sign that bacteria are getting ahead of you, and that is what turns stems slippery.

• Trim the stems with a knife rather than tearing or snapping them, which damages the cells.
• Keep the leaves out of the water. Submerged leaves rot quickly and taint the whole bunch.
• Change the water daily if you can manage it, or at least every other day.
• Pick out any yellowing sprigs before they spread mould to the rest.

Basil Is the One That Breaks the Rules

Basil is a Mediterranean plant that has never quite forgiven us for putting it in a cold box. Refrigerated basil blackens within a day or two, and the leaves lose their perfume. Instead, treat it more like a houseplant. Trim the ends, stand the stems in a glass with a couple of centimetres of water and leave it on the windowsill at room temperature, out of direct midday sun. Change the water every day and it will keep going for a week or more, often putting out small roots.

If you have bought a living pot of basil rather than a cut bunch, keep it on a bright windowsill and water it from the base rather than drenching the compost from above. Pinch out the top pair of leaves on each stem every so often; the plant will bush out instead of running to seed, and you get the pinched leaves for supper.

Keep Woody Herbs Dry and Cool

Rosemary, thyme, sage, oregano and bay come from drier climates and do not want the same treatment at all. Damp is their enemy — wrap them in a wet cloth and they will turn black. Keep them dry, loosely wrapped in a sheet of kitchen paper or a barely damp tea towel, then slipped into a bag in the vegetable drawer of the fridge. They will happily last a fortnight.

If you are not going to get through them, freezing is genuinely excellent for woody herbs. Strip the leaves from the stems, spread them on a tray for an hour, then tip into a bag. They will not be much good scattered raw over a salad, but in a stew or a roast they are every bit as good as fresh. Whole sprigs can go straight into the freezer too, ready to drop into a roasting tin.

Reviving Herbs That Have Already Flopped

Before you bin anything, check the stems. If they are still firm and only the leaves are limp, there is life in them yet. Trim the bases again, stand them in cold water and give them an hour — in the fridge for soft herbs, at room temperature for basil. Nine times out of ten they will lift and crisp up. Anything slimy, brown or smelling sour should go straight into the compost, since it will only speed up the decline of the rest.

Turning a Surplus into Something Useful

When you have more herbs than you can use, chop the soft ones finely, pack them into an ice cube tray with a little water or olive oil and freeze. The cubes drop straight into a pan later. You can also blitz a big handful with oil, garlic and a squeeze of lemon for a green sauce that keeps for a week in the fridge, or beat chopped herbs into soft butter and freeze it in a log.

None of this takes long — a minute at the sink when you get home from the shop, a daily glance at the water. Do it and you will find that herbs stop being something you buy and forget, and become something you actually cook with.