Growing Herbs Indoors in Winter: What to Sow on a Windowsill Now

There is a reason the supermarket basil always dies, and it is not your fault. An indoor herb pot in December fails for one reason above all others — light — and by December there is nothing you can do about it. Which is why the month to start a winter herb supply is not January, when the seed packets go on display, but now. Sow in the first half of September and your plants build their leaves while there are still thirteen hours of daylight, then coast through the dark on what they have banked. Sow in December and you get pale threads that fall over. Same seed, same windowsill, entirely different result.

• Sow indoors Sept–early Oct for a winter supply; again from February
• Best performers Chervil, parsley, chives, coriander, dill, rocket, mustard, cress
• Light Four hours of direct sun, or an LED strip for 12–14 hours a day
• First cut 4–6 weeks from sowing, then cut-and-come-again into March

Light is the limit, not warmth

Your house is warm enough for almost any herb; that has never been the problem. The problem is that a bright windowsill in late December receives a small fraction of the light the same spot gets in June — the sun sits far lower, the days are half as long, and window glass takes a further cut. Warmth without light is the worst possible combination for a seedling: the plant is metabolically awake, growing, spending, with nothing coming in. That is exactly how you get the pale, elongated stems described in our guide to leggy seedlings, and once a herb seedling has stretched it never thickens up again.

Sowing in September sidesteps the whole problem. A parsley or chervil plant that reaches a decent size by late October has a store of leaf and root to draw on; it will grow slowly through the winter rather than trying to start from scratch in the dark. Give it the brightest glass you have — south or west facing — and turn the pot a quarter-turn twice a week, because a plant leaning hard toward the window is telling you it is short of light. The same principle governs everything in our guide to growing in low light: leaves you can grow in dim conditions, fruit and seed you cannot.

Which herbs actually work indoors — and which waste a pot

The herbs that succeed on a winter windowsill are the fast, leafy, cool-season ones. Chervil is the outright star and almost nobody grows it: a woodland plant that bolts and sulks outdoors in summer, it genuinely prefers cool and shaded, so winter indoors is its best season. Coriander is the same story — it runs to seed the moment it is hot, and is far happier at 15 °C than 25 °C. Add parsley (slow to germinate but the longest-lived pot you will grow), chives, dwarf dill, and the peppery quick crops: rocket, mustard and cress, all of which are cuttable within a month.

The ones to leave alone are the Mediterranean woody perennials — rosemary, thyme, sage, oregano. They will survive indoors, but survival is not the point: the aromatic oils that make them worth growing are built from light, so a winter windowsill plant grows soft, pale and tastes of remarkably little. Sow those outdoors in spring instead. Basil sits in its own category — it wants both 20 °C and strong light, which no unlit windowsill offers between November and February. Sow it in spring, or accept that basil is the one herb that genuinely needs a lamp.

How to sow a winter herb pot, step by step

1. Pick a deep pot with drainage holes At least 15 cm deep, with a saucer under it. Parsley, coriander and chervil all send down a taproot, and a shallow decorative pot with no hole is the fastest way to kill them. Our container growing guide covers compost volume and drainage in detail.
2. Use fresh compost, never garden soil Garden soil compacts indoors, drains badly and brings in fungus gnats. Multipurpose compost with a handful of grit or perlite is ideal.
3. Sow it as a crop, not as a plant For rocket, mustard, cress and coriander, scatter seed thickly and treat the pot as a small bed you cut from. For parsley and chervil, sow five seeds and thin to two — they need the room. See indoor seed starting for the basics.
4. Germinate cool and bright, at 15–18 °C Not on top of a radiator. Coriander and chervil in particular germinate poorly above 20 °C, and warmth without light produces the exact seedlings you do not want.
5. Water far less than you think A winter pot barely evaporates. Lift it — if it feels heavy, wait. Overwatering kills more indoor herbs than cold, darkness and neglect combined, and soggy compost invites damping off.
6. Feed lightly from week six A half-strength liquid feed once a month is plenty. Pushing nitrogen at a plant that cannot photosynthesise gives soft growth that rots — the reasoning in our guide to feeding and fertilising.
7. Sow a fresh pot every three to four weeks Coriander, dill and rocket are sprinters, not marathon runners. Staggering them is simply succession sowing on a windowsill.

The windowsill problem nobody mentions

A windowsill is not one environment, it is two. Draw the curtains on a January night and the strip of air between glass and fabric can sit five to eight degrees colder than the room; by mid-morning a radiator underneath is blowing dry heat straight up into the same pot. Cold roots at night, desiccating air by day — it is a punishing cycle, and it explains a lot of otherwise mysterious indoor herb failures. Tuck the curtain behind the pots, or move them onto a table in a cold snap.

That dry radiator air brings the other winter problem: red spider mite, which thrives in warm, arid conditions and shows up as fine stippling and webbing on the undersides of leaves. Standing pots on a tray of damp gravel raises humidity around the foliage without waterlogging the roots. Our guide to common garden pests covers identification if you find something else living in there.

Grow lights, honestly

An inexpensive LED strip hung 20–30 cm above the pots and run for twelve to fourteen hours a day on a plug-in timer does more for winter herbs than any other single intervention. It is not necessary for chervil, parsley or chives on a good south-facing sill. It is genuinely useful for coriander and dill from November onwards, and it is the difference between success and failure for basil. If you are already extending the season outdoors with fleece and cloches — see extending the growing season — a lamp indoors is the same idea applied to the other limiting factor.

Common mistakes

• Sowing in December. The seed germinates and then has nothing to grow on. September and early October are the productive windows.
• Overwatering. Winter compost dries slowly. Lift the pot to judge it, and never leave one standing in water.
• Twenty seedlings in one supermarket pot. They are competing, not thriving. Split them into two or three pots or start again from seed.
• Sowing rosemary, thyme or sage indoors in winter. They will live, but they will not taste of anything. Save them for a sunny spring sowing outside.
• Picking single leaves. Cut a third of the pot back to 3 cm with scissors instead. It regrows evenly, and the plant stays bushy.
• Using garden soil or a pot with no drainage hole. Both end the same way.

Frequently asked questions

Which herbs grow best indoors in winter?
Chervil, coriander, parsley, chives and dwarf dill, plus quick cutting crops like rocket, mustard and cress. All are cool-season leafy plants that tolerate modest light. Browse the full herb seed range or the organic herbs if you prefer, and check what else is still worth sowing in our September and October collections.

Do I need a grow light?
Not for chervil, parsley or chives on a bright sill. Yes, in practice, for basil, and it noticeably improves coriander and dill from November. A cheap LED strip on a timer for twelve to fourteen hours a day is enough — you are topping up day length, not simulating the tropics.

Can I bring my outdoor herbs inside instead?
Mint and chives can be potted up and brought in, but expect them to die back first. That is dormancy, not death — and chives in particular crop far better if you leave the pot outside until it has taken a couple of frosts, then bring it into the warmth to force fresh growth. Mint and chives both respond well to this. Tender plants are a different matter — see overwintering tender plants.

Why are my indoor herb seedlings tall and floppy?
Too little light, almost always, sometimes with too much warmth alongside it. Move them to the brightest window you have, turn the pot regularly, drop the temperature if you can, and add a lamp if the position is genuinely dim. Stretched seedlings do not recover, so it is usually quicker to resow.

A windowsill will never be a greenhouse, but three pots sown this month will keep a kitchen in chervil, parsley and coriander until the light comes back — which is a better return than any supermarket pot has ever given. Browse the herb seed collection, the parsley, chervil and coriander ranges, or the faster microgreens and sprouts if you want something to cut within a fortnight. While you are sowing under cover, sweet peas are the other job for the coming weeks — and there is more in our September sowing guide, the wider growing guides library and the full sowing calendar. Sow cool, cut often, and water half as much as you were going to.