Growing Herbs Indoors in Winter (What Actually Survives My Kitchen Window)

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The garden has been put to bed for a few weeks now. The beds are under a layer of shredded leaves, the garlic is in, and the only green thing left outside is a clump of chives that refuses to quit. So the growing has moved indoors, to a four foot stretch of kitchen windowsill, which is the only place in this house that gets real sun in November.

I want to be honest about what growing herbs indoors in winter actually looks like, because most of what I read about it when I started was wrong. Not wrong exactly. Just optimistic in a way that set me up to kill things. The photos always show eight matching pots of lush basil on a white counter in what is clearly July light. That is not what my windowsill looks like in January, and it is probably not what yours looks like.

The short version

Light is the whole thing. Not soil, not pot size, not fertilizer. If you have a south or southwest window, you can keep chives, thyme, oregano, mint, parsley and bay going all winter with very little effort. If you do not have that window, you need a small grow light or you will spend three months watching plants stretch and pale and give up. And whatever your light is, you are growing a garnish supply, not a harvest. I get enough to finish a soup. I do not get enough to make pesto.

Your window is probably the problem

Most herbs want around six hours of direct sun. Some get by on four. Here is the part nobody says out loud: in northern Illinois in December we get about nine hours of daylight total, and a lot of those days are flat gray. A south window in June and a south window in December are not the same window.

Mine faces south and I still ended up adding a cheap LED strip light on a timer, about twelve hours a day, sitting a few inches above the pots. It made more difference than anything else I tried. If your only option is an east or north window, skip the window entirely and put the pots wherever the light goes, even if that is an unglamorous corner of the counter.

The other thing about windows in an old house: they are cold. Ours are original and they leak, which is a whole separate project I wrote about in how we keep this old house warm in winter. Most herbs are fine with a cool windowpane. Basil is not, which brings me to the part where I tell you what to stop buying.

What actually survives my kitchen window

Chives. The easiest one by a wide margin. I dig up a clump from the garden in October, cut it back, and it sulks for two weeks and then just keeps going. Snip from the outside of the clump, never shear the whole thing flat.

Thyme. Slow but reliable. It wants to dry out between waterings and it does not need much root room. Do not cut it back hard when you bring it in. Thyme does not like being asked to regrow everything at once in low light.

Oregano. Same care as thyme, grows faster, gets leggy if the light is poor. When it starts reaching, that is a light problem and not a water problem.

Mint. Thrives indoors, which should surprise nobody who has ever tried to get rid of it outdoors. Give it its own pot. It will choke out anything you plant with it.

Parsley. Worth growing from seed in a pot rather than transplanting, because it has a long taproot and hates being moved. Slow to start, then steady. This is the one I use most, mostly in stock and soup.

Bay. Not an herb you harvest constantly, but one small bay plant lives on my counter year round and gives me a leaf whenever I am building a pot of something. It asks for almost nothing.

What I stopped trying

Basil. I have killed basil indoors more than once and I am done trying. It wants heat and a lot of light, and a cold windowpane in a drafty farmhouse gives it neither. It drops leaves, then it gets sad and woody, and then you have a dead plant in February. If you want basil in winter, buy a bunch at the store and use it that week. That is not a failure of gardening. It is just the wrong season.

Cilantro and dill are the other two I would skip. Cilantro bolts fast and does not regrow well after cutting, so you are really doing a tiny succession planting every three weeks, which is more work than it sounds like. Dill has a taproot that resents pots. I grow both outside in spring and let them be a spring thing.

I would also skip the countertop hydroponic units. They do grow herbs. But they cost more than a grow light, they need pods, and a clump of chives in a terracotta pot does the same job for about four dollars.

How I pot them

Terracotta, every time. It dries out from the sides, which forgives the main mistake everyone makes indoors in winter. Make sure there is a real drainage hole and something under it to catch water. Regular potting mix is fine. Do not dig up garden soil for indoor pots, it compacts into a brick and it brings company.

Before I bring anything in from outside, I cut it back by about a third, check the undersides of leaves for aphids, and let it sit somewhere separate for a week if I can. Chives, thyme, rosemary and bay are the exceptions on cutting back. Leave those mostly alone.

Watering is where most of them die

Indoor herbs in winter need less water than you think, and much less than they needed in a hot July garden. The plant is growing slowly, the days are short, and the soil stays wet far longer. I water when the top inch is dry to my finger, and in December that is often once a week.

The one thing I check is whether the pot feels light. Soaking wet soil plus low light is the exact combination that rots roots and invites fungus gnats, which is the next thing I want to warn you about.

About the gnats

If you bring plants indoors, at some point you will get fungus gnats. They come from soil that stays damp at the surface. They are harmless to you and mostly harmless to the plant, and they are SO annoying.

Two things fix it. Let the top of the soil dry out properly between waterings, which breaks the cycle because the larvae live in that top layer. And put a couple of yellow sticky traps in the pots for the adults. That is it. I have never needed anything stronger than that.

How much you actually get

This is the expectation I wish someone had set for me. Six pots in a good window, in winter, in zone 5b, gives me enough to finish things. Thyme and parsley into a pot of stock. Chives on eggs. A bay leaf in chicken noodle soup. That is the real yield, and it is genuinely worth it, because those are the flavors I would otherwise be buying in a plastic clamshell and throwing half away.

The rule is to take less than a third of a plant at a time and to let it recover before you go back. In summer you can harvest hard and the plant bounces. In January it will not bounce. Harvest like you are borrowing.

Questions I get about this

Can I grow herbs indoors without a grow light?

Yes, if you have a south or southwest window and you stick to chives, thyme, oregano, mint and bay. Those five will hold on. Parsley will be slower. Anything that needs real heat and real sun, basil especially, will not make it through a northern winter on window light alone.

Why is my indoor rosemary dying?

Usually one of two things. Too much water, or dry furnace heat. Rosemary wants bright light, cool air and soil that dries between waterings, which is almost the opposite of a warm room with a heat vent under the window. Move it to the coolest bright spot you have and water less. Powdery mildew on the stems means the air around it is too still.

Should I bring my outdoor herbs inside or start fresh?

Depends on the plant. Chives, mint and thyme transplant in fine. Rosemary and bay can come in if they were in pots already. Parsley and anything with a taproot I would start new from seed indoors instead of digging up.

How long will indoor herbs last?

Perennials like thyme, oregano, mint, chives and bay will go for years if you repot them every couple of seasons. Parsley is a biennial and will give you one good winter and then want to flower. Basil and cilantro, if you insist, are a few weeks each.

What about the cat?

Worth thinking about before you set the pots down. Several common houseplants are toxic to cats, and while the culinary herbs on this list are not the dangerous ones, a chewed plant is still a dead plant. We have a cat, so the pots live at the far end of the sill and out of her way.

If you want to see what the outdoor side of this looks like, I wrote about putting the garden to bed for winter a few weeks ago, and about what actually grows well in a Midwest garden when the season comes back around.

For now there is a row of small pots at the far end of the sill, which is where most breakable things in this house have ended up since Lochlan started walking. There is something good about rubbing a thyme leaf between your fingers in the middle of February. It smells like the part of the year that is coming.