One of the things I love most about summer is having an herb garden right outside my back door. Oregano, basil, dill, tarragon, sage, lavender, parsley and several kinds of thyme are right there ready to snip and toss into soup, salad or whatever we’re making, anytime. Sadly, having fresh herbs at the ready is just a six-month pleasure here in the Arctic, so in recent years I’ve been trying to grow herbs indoors once the weather starts to turn cold. I say “trying” because, honestly, it has been a bit trying, literally. But I’ve worked out some kinks and I’d like to share what I’ve learned with you now.
By far, the biggest challenge when growing herbs indoors is lighting. I’ve read, and people have told me, that it’s possible to grow some herbs fairly well in a sunny window. I say those people don’t live in Minnesota in the winter — or maybe they try to see the good in spindly plants where I’m more in the “off with their spider-mite-infested heads” camp. There is one exception: chives. Chives do last a long time when grown in a sunny spot, and you can snip off what you need for months as long as you leave at least 2 inches of growth on the plant.
OK, I’ll add this too. If you grow rosemary in a pot outside in the summer, you can bring it indoors before temps dip into the 30s. I do this every year and my rosemary, which is now in an enormous pot, sits on a bench in my dining room in a sunny window looking more like a bonsai tree than an herb, which I suppose it kind of is at this point. Even though it gets lots of sun and enough water to keep it alive (but not too moist), it tends to look like gray, ragged death by April. But it always perks up when I bring it back outside in the spring.
A case for grow lights
If you’re a regular reader, you know I’ve often been a bit of a naysayer when it comes to grow lights and I’m only going to back off a little bit on that stance here. Overly pushed on novice gardeners who want to start growing their own plants from seed, grow lights are pretty spendy (though prices are coming down) and you don’t really need them for starting most seeds. For that job, cheap fluorescent tubes you can buy at any hardware store will do just fine.
Those same, inexpensive standard fluorescent lights work well for growing herbs indoors, too. But gardeners who are serious about their harvest may also want to check out compact fluorescent, metal halide and LED lights, as well. At the recommendation of an energy-efficiency-minded gardener friend, I’m going to try LEDs this year, so I’ll report back next season on how that goes. Whichever system you choose, lights will need to be kept a specific distance away from plants. Standard fluorescents, for example, should be 2 to 4 inches above plants where it’s more common for metal halide lights (depending on wattage) to be quite a bit higher, say, two to four feet. So read package directions.
Care and feeding
Just like they do outdoors, herbs prefer well-drained soil and will perish if kept too moist and soggy. You can start your herbs from seed in a soilless, seed-starting mix or, if you buy small herbs at a garden center or grocery store, they’ll already be in a standard potting mix. If you haven’t tried to overwinter herbs before and can shell out a few bucks, I would recommend buying small seedlings rather than starting from seed.
You’ll probably need to water your herbs weekly, but before you do, push your finger down into the soil about an inch. If it’s dry, water. If it’s not, wait a couple of days and check again.
Herbs don’t need a lot of fertilizer, but they will benefit from some added nutrients. I like to use fish emulsion, diluted to half the recommended amount and applied once a month. Fish emulsion smells a bit, but it’s a great organic fertilizer that doesn’t cause damaging salt buildup like many fertilizers do. That said, it’s fine to use synthetic fertilizers, such as Miracle Grow or Osmocote when growing herbs.
While you can’t harvest armloads of herbs from indoor gardens like you can outdoors in summer, you can certainly pick a fair number of leaves without being a plant murderer as long as you follow a few simple tips. Primarily, don’t harvest more than about a fourth of the plant at one time. Pinch a few leaves and then give your herb a little time to put on some new growth. As you pinch, you can create bushier plants if you remove the sprigs at the outer tips, and this is what you want because the alternative is really tall, leggy herbs that won’t produce much and they’ll look silly, too.
If you’re growing basil, cut the flowers off as soon as you see them to keep the plant healthy and focusing on leaf growth. Mint will need to be pruned constantly whether you use it or not to promote new leaves. Thyme is amazing and will just grow and grow no matter what you do. If you want cilantro and dill, you’ll need to keep planting those throughout the winter.
Meleah Maynard is a writer and Master Gardener. Her first gardening book, “Decoding Gardening Advice: The Science Behind The 100 Most Common Recommendations,” will be published in January by Timber Press.