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Tips for growing herbs and greens all winter

By John Lehndorff

If you bring a citrus tree indoors, don’t let it completely dry out or its leaves will turn yellow and drop like crazy. Water when the soil is barely damp, and feed the tree regularly with an organic fertilizer formulated for growth, not flowers. (photo: fotografas edgaras)
If you bring a citrus tree indoors, don’t let it completely dry out or its leaves will turn yellow and drop like crazy. Water when the soil is barely damp, and feed the tree regularly with an organic fertilizer formulated for growth, not flowers. (photo: fotografas edgaras)

When Michael Linsley moved to Boulder with his wife, Nancy, he faced a dilemma. “We lived in California and we were spoiled,” he says. “Anything will grow there. I got used to walking outside and harvesting food.”

He knew re-creating that bounty would be tough—“it’s much more challenging to garden in a four–season climate,” he says, and gardening entirely outdoors wasn’t feasible either, because of the deer and rodents populating his mountain property. “You end up having to build electrified wire cages around the plants, and I didn’t want a war with nature.”

So Linsley compromised by installing a small greenhouse off the living room, four outdoor concrete cold frames, and a large built-in kitchen planter that’s home to a variety of herbs, tomatoes and a kumquat tree.

He started gardening indoors much more modestly, though, with only a couple of containers. “The first time it was all herbs: basil, oregano, mint, cilantro—all useful culinary things,” he says. “After that came tomatoes, mainly cherry varieties in the winter.” Having enough pots is never a problem, since Linsley is a noted ceramic artist whose work is displayed at Black Cat Farm Table Bistro in Boulder.

Connie Smith, a horticulturist at Boulder’s Sturtz & Copeland, agrees herbs are the best choice for indoor winter gardens. “Plant already-started herbs—mint and basil are the easiest, and you can harvest them as they grow,” she says. Local nurseries typically offer a winter selection of basils, parsley, sage, thyme, cilantro, mints, tarragon and chives.

Plant herbs and greens in terra-cotta or glazed ceramic pots, or plastic trays that fit in front of windows. Indoor containers can be wide, 18-inches or more across at the top, but they don’t need to be deep, Smith says, because most herbs don’t have deep roots.

Minimizing Mistakes

Overwatering is the biggest mistake novice gardeners make. “Press your finger at least an inch into the soil to see if it’s really dry,” Smith says. Also, different plants need varying amounts of moisture. For instance, mint likes to be especially moist. Sage, thyme and rosemary like it a little drier. “When you do water, wet the soil until water starts seeping from the drainage holes,” Smith says. Linsley puts broken pottery and gravel at the bottom of his pots to help them drain better.

Beginners are often reluctant to pinch more than a few leaves from the top of a plant, especially basil. “Sometimes you need to bite the bullet and go way lower with your cuts,” Smith says, which allows for more leaf growth before the plant starts to bloom again.

Bugs are a problem that can discourage first-time gardeners. Basil and parsley tend to get aphids, Smith says, while sage is prone to spider mites. Rosemary and sage can get powdery mildew. Naturally derived sprays will take care of mildew, and insecticidal soaps and horticultural oils are available for aphids and spider mites. But if a plant doesn’t looks good, “I throw it in the compost,” Smith says.

Some outdoor herbs, including rosemary and basil, can be brought inside to overwinter, but check and treat for bugs first. Check the soil, too. “You need organic indoor-outdoor potting soil. If it’s just for growing outside you’ll bring in bugs,” says Corinna Bozella, who’s guided gardeners for seven years at The Flower Bin in Longmont.

Place indoor herbs where they’ll have good air circulation and not directly near a heating source. “They really like it draftier and cooler,” Bozella says. The same is true for lettuces and arugula, which can be grown from seed.

Smith and Bozella recommend three local seed companies: Lake Valley (www.lakevalleyseed.com) and Bounty Beyond Belief (www.bbbseed.com) in Boulder, and Broomfield’s Botanical Interests (www.botanicalinterests.com).

winter-greenery-BasileusSun, Soil and a Windowsill

Bozella’s best advice for beginners is to pay attention to your plants. “When it’s super cold, move plants away from windows,” she says, noting that plants need at least five hours of sunlight a day. Turn them occasionally so they don’t grow lopsided toward the sun.

She recommends fertilizing once a month with a good organic plant food meant to promote growing, not blooming (which is for flowers). Don’t overfertilize—a common mistake. Follow the recommended feeding instructions.

Linsley improves his harvests by using a worm composter to create soil and make “worm tea” to feed his plants. He also picks up Hazel Dell mushroom compost at the Boulder County Farmers’ Market. “That stuff is incredible. It turbocharges the soil, and vegetables grow faster.”

He’s particular about his seeds, too. “I like heirlooms and unusual varieties,” he says, noting that he’s a true foodie. “The whole point is to grow exquisitely fresh food you can’t get at the store.” He even grows a bay laurel and a lemon tree in indoor pots so he can have fresh bay leaves for pasta sauce and lemon juice for fish.

If his gardens produce to excess, Linsley makes homemade ketchup, barbecue sauce, eggplant chutney and tomato sauce. “I’m an evangelist for cooking your own food. It tastes better and you know what’s in it.”

Linsley is a big advocate for growing food in winter, or any season. “I do spend less on produce, and I spend less time and money driving to the store in Boulder.” But that’s not really the point, he says.

“Everybody can grow a container tomato plant, some chard and fresh herbs, and really connect to food. It’s gives you a warm glow to grow things, and there’s nothing quite like a homegrown tomato.”

A wealth of online information is available for indoor gardeners, but it’s easy to get overwhelmed. “Don’t overthink things,” Smith suggests. “A pot, soil, sun and a windowsill still work really well.”


winter-greenery-CBCKWays to Grow in Winter

Growing herbs and greens in winter is surprisingly easy to do. But some houses lack adequate southern exposure to ensure five hours of sunlight. If that’s the case, you could invest in some fairly low-tech equipment and lights.

The first step is to figure out how much growing space you have to determine how many lights you’ll need. “Even if you have a sunny place with southern exposure you may need lights,” says Jason Carver, manager at Way to Grow in Boulder. Lower-wattage full-spectrum bulbs of various lengths are perfect for herbs, lettuces and greens. (Sorry: No corn, celery or cabbage, unless you really want to crank up your electric bill.)

For first-time gardeners, Carver suggests a small system similar to his store’s display, which features bulbs installed in fixtures that plug into an outlet, and short black-plastic trays to hold the plants.

“If you water every other day, you should get a harvestable crop of lettuce and greens every month or so,” he says. Most herbs can be picked as they grow. Shallow trays are also ideal for growing nutrient-packed microgreens, which you can snip and put in salads.

Carver favors organic potting soil (not the potting soil intended for flowers), organic seeds, and distilled or filtered water.

He says a small indoor garden setup could include a 2-foot-long T5 blue-light light fixture ($72), two draining growing trays ($3), a large bag of Roots Organic soil ($24) and four organic seed packs ($8). Prices are approximate, but for about $100 you’d have everything to grow greens and herbs. The only extra costs would be water, electricity and additional seeds.

For those who want even simpler growing, Carver suggests countertop gardens from Boulder’s AeroGrow ($70-$350, depending on size). The lighted automated growing systems virtually feed (using Scotts Miracle-Gro) and water themselves.


John Lehndorff is the former food editor and features editor of the Daily Camera. He hosts Radio Nibbles at 8:25 a.m. every Thursday on KGNU 88.5-FM.