Growing Herbs on a Windowsill
A sunny windowsill can produce most of the herbs a kitchen uses, year round. It can also kill them in three weeks if you treat all herbs the same. The single biggest variable is where the plant evolved.
Two groups, opposite care
Soft, leafy herbs — basil, parsley, coriander, chives, mint, dill — come from temperate or tropical places with reliable moisture. They want rich mix, regular water and feeding. Woody Mediterranean herbs — rosemary, thyme, oregano, sage, lavender — come from dry, poor, alkaline hillsides. They want sharp drainage, lean mix, and to dry out between waterings.
Treat a rosemary like a basil and it rots. Treat a basil like a rosemary and it wilts and bolts. Almost every indoor herb failure is this confusion.
| Herb | Light needed | Water | Feed | Difficulty indoors |
|---|---|---|---|---|
| Basil | Bright, 4–6 h direct | Keep moist, never soggy | Weekly in growth | Easy in summer, hard in winter |
| Mint | Bright, indirect fine | Keep moist | Fortnightly | Very easy |
| Chives | Bright, 3–4 h | Moderate | Monthly | Very easy |
| Parsley | Bright, 3–4 h | Moderate | Fortnightly | Easy |
| Coriander | Bright, 3–4 h | Moderate | Light | Moderate — bolts fast |
| Thyme | Very bright, 5–6 h | Let dry between | Almost none | Moderate |
| Rosemary | Very bright, 6 h | Sparse | Almost none | Hard without strong light |
| Oregano | Very bright, 5 h | Sparse | Almost none | Moderate |
| Sage | Very bright, 5 h | Let dry between | Monthly, light | Moderate |
Light: the limiting factor
Behind glass, light intensity drops substantially compared with outdoors. A windowsill that reads as blazing to your eyes may deliver the equivalent of light shade to a plant. South-facing is best in the northern hemisphere, east or west acceptable, north-facing only for mint and chives.
Symptoms of insufficient light: long gaps between leaves, stems stretching toward the window, pale colour, and a plant that flops. The fix is more light, not more fertiliser. If you cannot provide it, a basic LED grow light on a 12–14 hour timer, positioned 15–25 cm above the plants, changes everything for about the cost of a few herb plants.
Containers and mix
Each herb in its own 1–3 L pot with drainage holes — this is important. A mixed "herb pot" from a supermarket looks lovely and fails within weeks, because the basil needs daily water and the rosemary needs to dry out, and they are sharing one root zone.
- Soft herbs: multi-purpose potting mix with a little perlite.
- Woody herbs: mix with 30–40% grit, perlite or sharp sand, and no slow-release fertiliser.
Those small pots of living basil are actually four to six seedlings crowded together competing for one small volume. Split them apart and pot each one individually and they will grow for months; leave them together and they collapse in two weeks.
Watering indoors
Indoor pots dry slowly and unevenly, and the usual killer is a saucer left with water in it. Water thoroughly, let it drain for 15 minutes, then empty the saucer. For Mediterranean herbs, wait until the top 4–5 cm is genuinely dry — for a small pot that might be a week in winter.
Indoor air is often dry, particularly in heated rooms. Grouping pots together raises local humidity slightly, and a tray of gravel with water below the pots (pots sitting on the gravel, not in the water) helps soft herbs in winter.
Harvesting to keep plants productive
Herbs grow back faster when cut correctly, and the method differs by type:
- Basil: pinch out the growing tip just above a pair of leaves. Never strip a whole plant. Regular pinching is what keeps it bushy instead of leggy and flowering.
- Parsley and coriander: cut outer stems at the base; the centre keeps producing.
- Chives: cut the whole clump 3 cm above the mix; it regrows fully in a few weeks.
- Thyme, oregano, sage: trim lightly and often, never cutting into old woody growth, which does not regrow.
- Rosemary: trim soft green tips only.
If any herb flowers, pinch the flowers off unless you want seed — flowering shifts energy away from leaf production and the flavour turns bitter.
Overwintering
Soft herbs are annuals in practice: basil will not survive below about 10 °C and is best resown each spring. Mint, chives, thyme, rosemary, sage and oregano are perennials that will overwinter indoors if they get light. Cut back watering dramatically from late autumn, stop feeding, and move them off cold windowsills at night — glass can be 5 °C colder than the room.
Common questions
Why does my supermarket basil keep dying?
Those pots contain several competing seedlings in a small volume, and they are usually placed too close to a window at night or over-watered. Split them into individual pots and keep them above 15 °C.
How often should indoor herbs be watered?
Check every two or three days rather than following a schedule. Water thoroughly, let it drain, then always empty the saucer — standing water is the fastest way to kill an indoor herb.
Why are my herbs tall and spindly?
Insufficient light. The plant is stretching toward the window. Move it closer to the glass, choose a brighter aspect, or add an LED grow light on a 12 to 14 hour timer.
Can I grow herbs from cuttings?
Yes for many soft herbs. Basil, mint and oregano root easily in water within a week or two; rosemary and sage root more slowly and more reliably in a gritty mix rather than in water.