Southern gardeners, on the other hand, seem to live on the opposite end of the spectrum. The scorching heat of summer drives gardeners indoors to cool off while the garden fries to a crisp. Though neither can expect to be as productive as a temperate climate gardener through all twelve months of the year, keeping fresh herbs available year-round is possible, and without the expense of specialized equipment and deluxe grow systems.
This chapter presents an honest look at what can be grown indoors on a windowsill and covers simple, effective strategies that can extend the outdoor growing season into months that were previously considered dead times.
Elevating the bed above the soil line is a simple place to begin. Raised beds (see here and here) warm up earlier in the spring—giving you a head start—and they stay slightly warmer as the season cools down so that you can squeeze an extra week or so from sensitive annuals such as basil and cilantro.
In the spring and fall, apply a thick layer of mulch to keep the soil and surface roots warm through nippy nights. An actual blanket made of burlap works, too, but it is heavy when wet, so be sure to cut big holes around plants to keep it from crushing their crowns.
During the hottest days of summer, mulch acts as a protective shield against the sun’s rays, slows down evaporation, and keeps the soil moist longer during droughts.
Candidates for mulch include the following, in order of preference:
• Straw
• Buckwheat hulls
• Leaf mold
• Well-rotted bark
• Shredded newspaper
• Cocoa shells
Cold frames are essentially bottomless boxes with removable glass or plastic lids. The boxes are set onto soil, sometimes dug in a few inches, and the clear lids let in light and retain heat like mini greenhouses. If you’ve got the space, a cold frame is a highly effective way to jump-start spring seedlings right in the garden, and a cozy place to grow salad herbs past the frost.
Cold frames can be made from all kinds of materials, including straw bales and metal or wood boxes. Make a sturdy frame from used timber, an old table, a wooden bookshelf, or your college futon. Make the top from salvaged glass windowpanes or a few more pieces of wood with heavy plastic stapled to the top. Attach hinges to allow the top to be easily lowered or propped up to let in air on sunny, hot days. Cold frames are difficult to use in a container garden but will work set on top of a planter box. Community gardeners can also set aside space in their plot for a frame as long as they don’t mind trekking out to the garden to open and close the lid.
A floating row cover is essentially just a light piece of cloth that is draped over plants to generate warmth or shade. Nowadays, garden shops sell cloth made from state-of-the-art materials that is ultralight with excellent ventilation. When going DIY, look for lightweight material with an open weave such as lace, netting, or your mom’s old sheer curtains. Choose white or lightly colored fabrics for heat, and dark fabrics when shade is what you need.
Surround tender annual and perennial transplants with plastic or glass bottles that have been filled with water. Secure the heavy bottles together with duct tape to prevent them from toppling over. The water absorbs the sun’s heat during the day and releases it to the plants at night.
This system creates a snuggly, miniature microclimate for your plants that is especially useful in the spring when night temperatures can dip suddenly and drastically.
Clear plastic bottles and milk jugs are the cheapest and easiest way to retain heat in a small space. Just cut the bottom off with a knife and you’ve got a miniature greenhouse that can be set over an individual plant or pot. The bigger the bottle the better, which is why I hoard and stash the largest water jugs when I’m lucky enough to find them. Glass cloches are admittedly a lot nicer to look at than plastic. Make your own from recycled juice jars and wine jugs using a ’70s-era bottle-cutting tool kit. Turning over vintage Mason jars also works well, but you’ll need to keep an eye on the plants because they can croak inside without ventilation.
Once it gets too cold or too hot outside, cold- and heat-sensitive herbs can be brought indoors to live alongside your houseplants. Bring cold-sensitive crops indoors before nighttime temperatures dip down below 45°F or before the first frost. Start early if you’ve got a lot of plants so you’re not saddled with a living room full at the very last second.
Don’t bother bringing in plants that look sickly, diseased, or pest-infected—indoor life is hard enough on plants, and only the strongest will survive.
To prepare plants to come inside:
• Give leaves and stems a once-over and pick off any obvious pests like snails, slugs, or caterpillars by hand.
• Set pots in a bucket of water with a few added drops of natural dish soap and/or neem oil and soak for a couple of hours to take care of any critters that may be lurking in the soil.
• Another trick is to give the foliage and soil a refreshing shower with a hose, spray bottle, or watering can with a rose (a perforated nozzle) attached to wash off grime and tiny insects.
Container-grown plants are easy enough to shift inside, but in-ground plants will need to be dug up and potted into fresh container soil. Yes, it is an added hassle, but even the best in-ground soil will get compacted in a pot and rot your plants’ roots in no time.
1. Reduce your plants’ trauma by digging well around their rootballs.
2. Lightly shake or wash off as much ground soil as you can without disturbing the roots.
3. Transplant the plants into pots that are slightly larger than their remaining root mass and filled with fresh potting soil.
It’s okay to clip some roots back a bit if you need to downsize for space. Scented geraniums, tender sages and lavender, and basil are also excellent candidates for cuttings if you want to go even smaller yet and preserve just a piece of the plant for next year’s garden. See here for instructions.
Regardless of whether they prefer sun or shade outside, all herbs are going to need the best light you can provide within your home. Unless you live close to the equator, winter days are generally much shorter than in summer. The sun also shines differently; sometimes the light is dimmer or hits your windows at a less direct angle, even when they are south-facing.
Not everyone can afford the price tag or space to house a hard-core lighting system, but I’ve managed to keep a couple of überfussy plants alive with a clamp-on 10" metal reflector light and a full-spectrum compact fluorescent.
I’d advise against using incandescent bulbs, but if you do, be mindful of where you rig them up—they get dangerously hot!
The truth is that some herbs perform better indoors than others, and a few, no matter how hard you try to keep them alive, simply can’t hack it. It’s not you; it’s your home. Outdoors, plants are subjected to temperature fluctuations (warm days and cool nights), rain, wind, and more intense full-spectrum sunlight.
I’ve rated the following plants by their fussiness indoors so you know what you’re in for next winter.
Little-known Cuban oregano (tastes like common oregano) is the one herb anyone can keep alive no matter how bad the growing conditions. Mine once survived a full month of total neglect and has gone on to thrive and spawn more new and healthy offspring than I can give away.
No matter what you do, chili peppers, stevia, and even scented geraniums tend to look scraggly and a bit worse for the wear after months on a windowsill. But if you can keep them going through the winter, they’ll experience a new lease on life after a haircut and a month back outside in the spring.
Rosemary seems difficult, but the mistake is ours. We jump to coddle; however, it’s actually a pretty cold-tolerant plant and prefers to stay outside a wee bit longer than other tender perennials. Bring it in right after it has had a chance to experience a touch of frost. Other cold-hardy perennials including thyme, marjoram, tarragon, oregano, and garden sage also benefit from this treatment.
Unfortunately, sweet basil, the one herb we all want most, is the hardest to grow long-term indoors. With some experimentation I’ve found that basil varieties with textured leaves such as ‘Purple Bush’ and ‘African Blue’ live longer and happier than their soft-leaved counterparts. If you must have fresh sweet basil year-round, consider short-term growing. Short-term is also the way to go with other annuals including dill, fennel, cilantro, and cress.
Keeping Prima Donnas Cozy
Stevia and basil are particularly sensitive to chilly, wet soil caused by drafty winter windowsills. To keep them comfortable:
• Line cold sills with a piece of wool, felt, or old towel to keep pots from absorbing cold through the bottom.
• Keep the entire pot toasty warm with a homemade plant sweater or cozy. Cut the sleeves off an old sweater that was accidentally felted in the wash or sew a tube shape from an old towel or moth-eaten blanket. If you can knit or crochet, make a tube from wool or cotton yarn and add some decorative scallops on top for added flair.
Adjusting to life indoors where light and humidity are lower can be hard on some plants. Leaf drop is normal, especially in the weeks after they’ve been transitioned from the outdoors. Here are a few easy tricks to make your plants feel at home inside:
• Treat your plants to a good soak underneath the shower now and again using room-temperature water set on a low spray. This trick can work wonders and is especially useful to remedy infestations of aphids, whitefly, or spider mites. See Chapter 5 for further insight into specific pests.
• Moderate how much and how often you water pots depending on the conditions in your home. Plants set on chilly windowsills tend to stay wet much longer than those kept near drying electric baseboard heaters. Most houseplant herbs do not like to sit in cold, wet soil for extended periods of time, and they prefer it when the top inch or so of soil dries out slightly between waterings.
• Cut back on fertilizers or completely stop all together until just before the growing season returns. Fertilizers force plants into a growth spurt that weak winter sunlight cannot support. Plants end up growing elongated, floppy stems with stunted, sad foliage.
• Prune your plants back regularly to encourage lots of new, bushy growth.
Keeping your plants in an active state of growth is the way to go if you’d like fresh herbs through the off-season. However, in some situations, you may be better off keeping plants alive in a dormant state, and then coaxing them back to active growth when the growing season rolls around again.
Lemon verbena, Mexican oregano, stevia, fruit sages, and other tender perennials that grow into large bushes with woody stems in a warmer climate seem to do best when they are pruned back hard—almost down to stubby stalks—and put to rest for the winter. Set the plants in a cool but not freezing location with windows, such as a cold greenhouse, apartment building hallway, garage, or basement, and water when the soil has dried slightly.
