Can you grow vegetables indoors in the winter? I’m not talking here about starting seeds indoors you’ll be planting outdoors later, but rather vegetables you can really grow in your home during the dark days of winter. The grocery list would include tomatoes, peppers, lettuce, and others: the same veggies you normally grow outdoors during the summer. Is that possible?
My answer is a very timid yes, but it isn’t going to be easy.
Lack of Light
The limiting factor in growing vegetables indoors in the winter is light. Meeting the plants’ other needs is simple enough. We already heat our homes and vegetables need about the same temperature as people. Watering is easy to organize (just don’t forget!) and there is a wide range of soils, fertilizers, pots, etc. you can use. But where are you to get the intense sun that vegetables prefer?
That’s not a problem in the summer outdoors or even indoors in front of a large south-facing window, but in autumn and winter, with their short, gray days and the sun’s reduced intensity, it’s just not so easy to succeed.
But don’t lose all hope: there are still a few possibilities. Here are some, from easiest to most complicated.
Many vegetables and grains are a snap to sprout and the only equipment you need is a Mason jar and a piece of plastic mosquito screen. Plus the technique is certainly simply enough.
Just pour about about 1 or 2 tablespoons of seeds into the jar. Cover the opening with a piece of mosquito screen and hold it in place with the metal screw band of the lid (you won’t need the flat part of the lid). Now cover the seeds with 2 inches (5 cm) of cool water and soak overnight. In the morning, drain, then pour in more cool water, swish the seeds around to rinse them well, then drain again. From now on, twice a day, pour in enough cool water to cover the seeds, shake a bit, then drain well. Your sprouts will be ready in about 5 to 10 days (each type has its own schedule). You’ll known they’re ready when there are roots visible, but before the first leaves (cotyledons) have fully developed.
No light at all is needed at first, but after two or three days, a bit of natural sunlight will give greener sprouts. You’ll have to experiment a bit on that level: some people find paler sprouts tastier than green ones.
Keep several sprouting jars going with various seeds at various stages of maturity so you’ll have something to harvest daily.
Why are sprouts so easy to grow? Because you harvest them at a very young stage, before the lack of intense light harms them… and before anything has time to go wrong!
These are much almost the same as sprouts, but you sow the seeds in soil… and harvest them a few days later than sprouts, in about two weeks, when the cotyledons (first leaves) are fully developed. For microgreens, more intense lighting is required or they will etiolate (stretch for the light). A place on a sunny window (winter sun does suffice) or under a fluorescent lamp, for example, will be needed.
You can harvest microgreens with scissors, cutting them off at the base, or pull them out of the potting mix and rinse them well to remove any soil particles, as their roots are edible too.
Here are some vegetables, herbs, and cereals that make delicious and easy-to-grow sprouts and microgreens:
- mung bean
- soy bean
3. Salad Greens Under Artificial Light
Leafy vegetables require less light than fruit-producing vegetables and root vegetables and ripen more rapidly. That means you can grow them without too many complications. However, not in front of a window in the fall or winter: there just won’t be enough light to grow healthy leaves. However, with a simple shop-type 2-tube fluorescent lamp suspended over a table or a shelf, you can grow leafy vegetables anywhere: in the basement, the attic, under a staircase, in a closet, etc.
You’ll have a choice to make when it comes to buying a lamp. Until very recently, T12 fluorescent lights (the kind you see everywhere in stores and office buildings) were the most widely available and the cheapest. However, they are now considered a bit inefficient. A newer format, the T8, with narrower tubes, is catching on more and more. It is more efficient that the older T12, but has been, until recently at least, considerably more expensive. Both do a great job growing leafy vegetables. And in case you wondered, T12 tubes will only fit T12 lamps and T8 tubes, only T8 lamps. The jury really is still out on this, so I suggest buying whatever lamp best suits your budget.
Whatever kind of lamp you choose, buy Cool White tubes or their equivalent. They are the cheapest on the market and amply suffice for growing leafy greens. You don’t need the very expensive full-spectrum horticultural tubes when your are “just” growing greens. (They were designed to stimulate bloom and bloom is the last thing you want leafy vegetables to do!)
You’ll likely only be using your fluorescent tubes for about six months a year, so they ought to last for 6, 7 or even 8 years. Change the tubes when they begin to darken at the ends.
Finally, you’ll need an inexpensive timer to make sure your plants get the light they need each day. I set mine to 14 to 16 hours to encourage a bit of extra growth.
Growing leafy vegetables under lights is certainly simple enough to do. Just fill pots or trays with moist soil (I prefer potting mixes that contain mycorrhizae, a beneficial fungi) and sow the seeds about ½ to 1 inch apart (1-2 cm), barely covering them with mix. Adjust the height of the lamp so it is about 6 inches (15 cm) above the trays or pots. As the plants grow (and they’ll grow very quickly!), raise the lamp so it remains about 6 inches (15 cm) above the plants themselves.
Water as needed when the soil is dry to the touch, adding a little seaweed fertilizer to the irrigation water when you do.
How you maintain your plants as they grow depends on you, though.
Some gardeners like to grow their vegetables well-spaced so each produces a nice individual rosette. If so, transplant the seedlings into individual 4- to 6-inch pots (10-15 cm) when their leaves start to touch. The maturity rate will vary, but, to give you an example, most lettuces will form a beautiful small but ready-to-harvest rosette in 40-60 days.
I prefer to harvest my greens without going through the hassle of transplanting. This close spacing gives a sort of hodgepodge of leaves where the individual plants aren’t too recognizable, but they will be ready to harvest sooner, in about 20 to 30 days, when they are about 6 inches (15 cm) tall. Just cut them about ½ inches (1 cm) from the ground… and let new leaves grow back. This “cut and come again” method normally gives a second harvest, sometimes even a third.
With either method, make successive plantings from early fall right through the winter so you’ll always have fresh salads to harvest right through until the outdoor gardening season begins.
You can grow most leafy vegetables following one or the other of the methods described. If you’re just starting out, I suggest trying mesclun (a mixture of greens): it will give you a bouquet of flavors in little space. Or sow individual varieties, like lettuce (leaf lettuce grows the fastest), spinach, arugula, beet (for its leaves), etc. You can also grow several herbs this way, notably basil, coriander (cilantro), and parsley.
As for root vegetables, the easiest to grow indoors is certainly the spring radish: just follow the method described above. For other root vegetables, use deeper pots, space the plants more carefully… and stick to baby vegetables: baby carrots, baby beets, etc.: they’re faster to mature. It isn’t as easy to grow full-length root vegetables in a pot.
4. Combine Sun and Artificial Light for Fruiting Vegetables
I’m not a great fan of growing fruiting vegetables (tomatoes, cucumbers, eggplants, beans, etc.) indoors for a winter harvest. They tend to be very tall, very needy plants that grow weakly when they don’t get enough light. Plus they are slow to mature, taking months, not weeks like leafy vegetables… and the longer you grow a plant under less-than-ideal conditions, the more things are likely to go wrong. But if you insist on trying…
The cheapest way to go is combine natural sunlight and artificial lighting. You could, for example, hang a 4-tube (for greater intensity) fluorescent lamp over plants placed near the brightest window possible, raising the lamp as the plants grow (keep them about 6 inches/15 cm from the top of the plants ). I suggest using dwarf varieties of fruiting vegetables, such as those designed for growing in pots: small determinate tomatoes, patio cucumbers, dwarf French beans, etc. That’s because it is very difficult to adequately light tall plants under fluorescent lamps: usually only the upper leaves get enough light and the lower leaves struggle.
5. Or Convert a Room in Your Home Into a Grow Room.
This is the same technology commonly used for growing marijuana indoors: 400- or 1000-watt high density discharge lamps or powerful LEDs installed on the ceiling providing light as close as possible to sunlight in intensity and in quality. This might require major modifications to your home: an additional electrical box, a special air conditioning system, a CO2 generator, etc. Expect to pay handsomely just to get started… You can grow your veggies in potting soil or hydroponically: the choice is yours. As you can imagine, though, you’ll have to grow a lot of vegetables to make this veggie grow op worthwhile.
A Final Word
So, going back to our original question, about whether it is possible to grow vegetables in indoors even in winter… Yes, it is, but I still suggest sticking to sprouts, microgreens and leafy vegetables. Leave the fruiting veggies to real indoor vegetable gardening maniacs… or just wait until summer and grow them outdoors which is, after all, where they prefer to be!
This text was first published on this blog on November 5, 2015. It has been revised and the layout updated.