Keeping herbs: fridge, freezer, drying, and what never to do

Everyone who grows herbs hits the same problem: you harvest a lot at once and can’t use it in time. Coriander wilts, Thai basil turns black, lemongrass dries out at the back of the fridge. This article sorts herbs by how to keep them, in the fridge, in the freezer or dried, and covers the safety point you need before putting herbs in oil.

The fridge: fresh leaves you will use within days

Coriander, spring onion, parsley and mint all work the same way, following Health Canada’s advice.

1. Pick off yellow, bruised or black-spotted leaves and trim the stem ends.
2. Don’t wash them yet. Wash just before use.
3. Lay them on a damp, wrung-out paper towel and roll it up.
4. Put the roll in a zip-top bag or a lidded box in the crisper drawer.

This keeps them for about 5 days. The damp towel stops the leaves drying out, and the bag or box shields them from the cold, dry air in the fridge.

Basil: the exception that hates the cold

Basil is chill-sensitive. A 2023 review of research on storing basil (Thai basil is the same species) found leaves start to suffer below about 12°C and are severely damaged below 10°C, with dark spots, browning and wilting. Most home fridges are much colder than that.

The usual approach is to stand the stems in a glass of water like cut flowers, in the kitchen out of direct sun and away from the stove, changing the water daily or when it turns cloudy. If it must go in the fridge, wrap it, put it on the least cold shelf, and use it quickly. Holy basil and lemon basil bruise just as easily, so try the same method and watch how they do.

The freezer: lemongrass, galangal, makrut lime leaves, chillies

Firm herbs that go into soups and pastes freeze well. Their aroma survives into the pot, although they soften after thawing, so use them in cooked dishes rather than raw ones.

• Lemongrass: wash, remove dry outer leaves, cut into lengths or slice thinly the way you usually use it.
• Galangal, turmeric: wash and scrub off soil, pat dry, slice into rounds.
• Makrut lime leaves: wash, pat dry, keep whole and tear when cooking.
• Chillies: wash, remove stems, pat dry, keep whole or slice.

Dry them well before freezing; water on the surface turns into ice that glues pieces together. For soft herbs like coriander, Health Canada suggests chopping or puréeing them, pressing them into an ice-cube tray, covering with water and freezing, then adding the cubes near the end of cooking.

Example: tom yum kits in the freezer

Say one harvest gives you 12 lemongrass stalks, a galangal rhizome about 15-20 cm long and 30 makrut lime leaves, and your household uses 2-3 stalks of lemongrass, 5-6 slices of galangal and 4-6 lime leaves per pot of tom yum.

1. 12 lemongrass stalks ÷ 2-3 per pot = 4-6 kits
2. Galangal sliced about 3-5 mm thick from a 15-20 cm piece gives roughly 30-60 slices, enough for 5-12 kits
3. 30 lime leaves ÷ 4-6 per pot = 5-7 kits
4. Lemongrass runs out first, so you get about 4-6 bags per harvest; bag the extra galangal and lime leaves separately

Put one kit in each small zip-top bag, press out the air, lay the bags flat so they freeze quickly, and write the date on each. On cooking day, drop one bag’s contents straight into the pot without thawing. Use them within about 3 months while the aroma is still good.

Drying: which herbs are worth it

A Purdue Extension guide (adapted from Penn State) puts it plainly: tougher-leaved herbs are the easiest to dry, while tender-leaved herbs such as basil and mint hold a lot of water and will go mouldy if they don’t dry quickly. Health Canada also says drying works best for woody herbs.

In a Thai kitchen, soft, fresh-smelling herbs such as Thai basil, coriander and mint are usually better kept in the fridge or freezer. Tougher leaves are worth trying dried; smell them against fresh ones to judge.

How to dry

Method	How	Notes
Air-dry in shade	tie small bunches and hang them upside down somewhere dry and airy, out of direct sun, covered with a paper bag punched with holes to keep dust off, about 1 week	keeps the most aroma; in the rainy season high humidity slows drying and risks mould
Low oven	Health Canada uses 75°C for about 30 minutes; Purdue uses the lowest setting, no higher than about 82°C, with the door open, for 3-4 hours	fast, but heat destroys much of the flavour and colour

They are dry when the leaves are crisp and crumble easily. If they are still soft or leathery, don’t store them yet.

Storing dried herbs, and for how long

• Use an airtight container, such as a glass jar with a tight lid.
• Keep it somewhere cool, dry and dark, like a cupboard, not beside the stove, the sink or on a windowsill.
• Store leaves whole and crumble them when cooking; whole leaves hold their aromatic oils longer.
• Label the jar with the herb and the drying date.

Purdue says most dried herbs keep well for up to about a year. Let your nose decide: when the aroma fades, it is time to replace them. Moving jars of dried herbs in and out of the fridge causes condensation inside, and the damp can spoil them.

Safety: mould, and herbs in oil

Mould. Throw away fresh herbs that are slimy, rotten or smell wrong. If dried herbs show mould, throw out the whole jar, because the small pieces are mixed all through it.

Garlic and herbs in oil is the risk people most often miss. Oregon State University Extension explains that garlic, herbs and other low-acid vegetables covered in oil sit without air, a condition in which Clostridium botulinum, the cause of botulism, can grow.

• Homemade fresh garlic or fresh herbs in oil, and even dried herbs in oil, must be refrigerated and used within 4 days, or frozen for longer storage.
• Pesto and other blended herb-and-oil sauces follow the same 4-day rule.
• Label the jar with the date you made it and the use-by date, 4 days later.
• Never keep them at room temperature. Shop products that sit on the shelf have been acidified in a controlled process; homemade versions have not.

Homemade herbs in oil: 4 days in the fridge, or the freezer. There is no third option.

Home-grown herbs last longer than you might think once you know which go in the fridge, which go in the freezer and which are worth drying. Even a small bed behind the house can keep the kitchen supplied for a month.

Sources

• Storing fresh herbs, Health Canada (Canada’s food guide)
• Let’s Preserve: Drying Herbs (HHS-812-W), Purdue Extension, adapted from Penn State Extension
• Herbs and vegetables in oil (SP 50-701), Oregon State University Extension
• Preharvest and postharvest techniques that optimize the shelf life of fresh basil: a review, Frontiers in Plant Science (2023)