Which herbs grow well indoors, how much light they need, how to water and feed them, and how to keep supermarket pot herbs alive for more than a week.
The short answer¶
The limiting factor indoors is light, not warmth or water. A windowsill in a British winter gets a small fraction of the light of a summer garden, and even a bright room a metre back from the glass is much dimmer than it looks to the eye. Herbs grown in poor light go pale, stretch towards the window and lose flavour. Put them on the brightest sill you have — south or west-facing — turn the pots every few days, and accept that from roughly November to February growth will slow almost to nothing unless you add a grow light.
Which herbs do well inside¶
| Herb | Indoors? | Notes |
|---|---|---|
| basil | Very good | Wants warmth (at least 15 °C, ideally 20 °C+) and the sunniest spot. Dislikes cold draughts and cold water. |
| parsley | Good | Tolerates less light than most. Deep pot for the taproot. |
| chives | Good | Snip regularly; can be dug from the garden in autumn and potted up. |
| mint | Good | Vigorous; repot or divide every year. Keep moist. |
| Coriander | Short-lived | Bolts quickly in warm rooms. Sow a pinch every three weeks and treat as a cut-and-come-again crop. |
| chervil | Fair | Likes cool, bright conditions — an unheated porch is ideal. |
| thai basil, holy basil | Good in summer | Even more heat-loving than sweet basil. |
| lemongrass | Good | Root supermarket stems in water, then pot up. Keep above 10 °C. |
| Curry leaf | Good but slow | Needs warmth and bright light; loses leaves if cold. |
| rosemary, thyme, lavender | Poor | They need very high light and dry air circulation; indoors they tend to become weak and suffer mildew. Better outside in pots. |
| Bay | Fair | Tolerates a cool, bright room or conservatory. |
Light and grow lights¶
As a rule of thumb, leafy herbs want at least four to six hours of direct sun, and sun-lovers such as basil more. From autumn to early spring that is simply not available through most British windows.
A modern LED grow light makes indoor herb growing far more reliable. Look for a full-spectrum light that can sit around 15–30 cm above the plants (follow the maker's guidance on distance) and run it on a timer for 12–16 hours a day. Ordinary household LED bulbs are better than nothing but produce much less usable light for plants. Signs of too little light: long pale stems, big gaps between leaves, and plants leaning hard towards the window.
Compost, pots and watering¶
- Pots must drain. Decorative outer pots are fine, but tip out any water that collects in them half an hour after watering. Standing water is the commonest cause of indoor herb death.
- Compost. A good peat-free multipurpose compost suits leafy herbs; add a couple of handfuls of perlite or grit for better drainage. For bay and woody herbs use a soil-based compost.
- Watering. Water when the top 2 cm of compost feels dry, thoroughly, until water runs from the bottom, then let it drain. Little and often keeps the surface wet and the roots dry, which is the wrong way round. Basil prefers watering in the morning with room-temperature water.
- Feeding. Once a month in spring and summer with a half-strength balanced liquid feed is plenty. Heavily fed herbs are soft and less aromatic.
- Humidity. Central heating dries the air. Grouping pots together on a tray of damp gravel helps, and keeps them off hot radiator shelves.
Rescuing supermarket pot herbs¶
Supermarket "living herbs" are grown fast under ideal conditions, with dozens of seedlings sown into one small pot so that they look lush on the shelf. At home they compete for water and light and often collapse within a fortnight.
💡 Divide and repot
As soon as you get it home, tip the plant out of its pot and gently tease or cut the root ball into three to five smaller clumps. Pot each clump into its own 10–13 cm pot of fresh compost, water well and keep out of full sun for a couple of days. The divided clumps will grow into sturdier plants that last for months rather than days. This works well for basil, parsley, coriander and mint.
Harvest divided plants lightly for the first couple of weeks while the roots recover.
Harvesting indoor herbs¶
Pick often but lightly — no more than a third of the plant at a time. Pinch basil just above a pair of leaves to make it branch; take parsley stems from the outside of the clump; cut chives to about 3 cm from the base. See harvesting herbs for more.
Pests indoors¶
Indoor herbs have fewer pests than garden ones but are prone to a few:
- Aphids (greenfly) cluster on young shoots. Rinse them off in the sink or squash them.
- Whitefly fly up in a cloud when disturbed; yellow sticky traps help.
- Fungus gnats — tiny black flies over the compost — are a sign the compost is staying too wet. Let it dry out more between waterings.
- Red spider mite thrives in hot, dry rooms and causes fine mottling and webbing. Raise humidity and wipe or spray leaves with water.
Because you will be eating the leaves, avoid pesticides not specifically approved for edible crops, and follow label instructions to the letter.
Common mistakes¶
- Putting pots on a windowsill above a radiator: too hot and dry at the roots, too cold at the glass at night.
- Leaving plants trapped between a closed curtain and a cold window on winter nights. Basil in particular hates it.
- Expecting year-round harvests without extra light. A winter windowsill is a place to keep herbs alive, not to grow them hard.