Editor’s note: This article has been updated.
When I first started out as an urban farmer, my attempts to extend the growing season were limited to ‘Early Girl’ tomatoes and throwing plastic on things. Now I know the real secret to increasing production is to use every inch of space for the longest possible time.
This includes planting intensively using specialized plant spacing, growing vertically, and using space that would never be considered farmland. Growing indoors is just an extension of this mindset.
If you’ve ever wondered how to grow vegetables indoors in winter, read on.
Striking a balance
What vegetables can you grow indoors in the winter? The answer depends on several factors. If you have experimented with indoor growing, you may have noticed that plants don’t often last as long or produce as much as they would outside—despite an apparently perfect climate. Common culinary herbs like basil, cilantro, mint, and oregano will grow quite happily in a small pot in your kitchen window, but during the off season their production is often shorter because light is limited. However, with the right setup and the right varieties, it is possible to be successful growing food inside all year long.
Getting started with indoor growing
The key to successful indoor veggie growing is creating the right environment and sticking to a few varieties that do well. I’ve had particular success with herbs, Swiss chard, tomatoes and microgreens, some of which I’ve grown commercially.
Together these offer enough variety to make a serious contribution to your winter vegetable consumption. But, don’t take on all of these at once; first, focus on herbs, which can ease you into winter growing and provide a welcome addition to your meals.
Next, consider your exposure. If your indoor environment is low on natural light, you have a few options:
- Keep planting continuously over the winter
- Put the plants in a sunroom or temperature-controlled greenhouse
- Use a grow closet or cabinet
Grow closets: the controlled indoor environment
If you have ever wondered where to start growing vegetables indoors, we have two words for you: grow closet.
A grow closet doesn’t have to be an actual closet. Any closed-off area where you can control the environment, such as the corner of a room or a basement, can do the job.
Grow closets are often covered with reflective material such as foil or space blankets, although this isn’t a hard-and-fast rule. The foil maximizes the light in the room, which is provided by fluorescent grow lights. Putting together a grow closet is a lot cheaper than adding a sunroom to your home and more productive.
If your budget permits, grow cabinets are an even better option. These hydroponic systems provide light, nutrients and ease all in one.
Choosing a grow light
Grow lights maximize production even if you have natural light from windows. For the small home grower, these need not be expensive or complex. A good middle-of-the-road, high output lamp for growing food is the T5, which may seem pricey but will have direct results in production. This option is also far less expensive than the high intensity discharge (HID) lights used by commercial growers and doesn’t put out much heat.
The most common setup is a series of shelves with a light fixture on the underside of each shelf, installed on an adjustable chain that can be raised or lowered as needed over the plants on the shelf below. High commercial storage shelves work well for this because they have a lot of space for tall plants like tomatoes.
Alternatively you can use sturdy planting tables. To save space, you can also use a modular system meant for seedlings and indoor gardening.
Controlling temperature and humidity
Another important criterion for growing vegetables indoors is adequate ventilation. One of the biggest issues often encountered is fungus, because of the high humidity in most homes.
Herbs (and the plants listed except for tomatoes) prefer cooler temperatures: 62-72° F and humidity at 15-30%. The simplest solution is a fan or two, and possibly a dehumidifier. A cheap temperature and humidity reader attached to the shelving only costs about $20 and will allow you to make adjustments without guesswork. or
How to grow herbs indoors.
Although you could bring in plants from outside, it’s much better to start herbs from seed or use purchased starts. You don’t want to bring contaminants from the ground into your clean environment.
It’s also important to read up on your plants so you understand their particular needs, but in general, when growing herbs indoors, the following applies:
- Basil: Provides a continuous harvest over a few plantings. Use globe basil because it’s smaller.
- Cilantro: Use staggered plantings. Cilantro doesn’t produce a continuous harvest.
- Oregano: Buy as starts. It’s a perennial, so the plant will come back.
- Mint: Grows well from cuttings.
When planting seeds, don’t turn the lights on your plants until they have true leaves. Once you do begin, regularity is important. The lights need to be on 12-16 hours a day with 8 hours of darkness, and plants need regular watering that keeps them just moist.
Watering inside without ruining your flooring can be done carefully using a spray bottle. I have also employed a pump pressure sprayer commonly used for pesticides because they provide a very even spray. If you have a wooden floor, installing a rubber mat under the shelving is a good way to protect against spills.
How to grow tomatoes indoors.
Hopefully at this point you’ve successfully planted, grown and harvested herbs with adequate ventilation, lighting, watering, humidity and temperature in your grow closet or cabinet. You’ve probably made some adjustments to try to get things just right, but herbs are very forgiving and you’ve seen some success. Now it’s time to experiment with some real vegetables.
Controlling powdery mildew and other fungi
The first issue to address proactively is fungus, which herbs can resist a little more than vegetables. With fans and a dehumidifier strategically placed to create airflow, you may not have an issue at all. However, in a moist climate like the Pacific Northwest, even that may not be enough.
Powdery mildew is the most common disease of houseplants and it spreads quickly indoors, covering leaves in faint white spots that eventually kill the plant. Powdery mildew thrives in an environment of 70° F with poor air circulation, and it doesn’t mind dry conditions.
Airflow with a fan will prevent the disease, but if you get an infection, isolate the plant and pinch off the affected parts. Mix 1 tablespoon of baking soda, half a teaspoon of liquid soap and 1 gallon of water. Spray on all parts of the plant, making sure to get the undersides of leaves.
The other necessary prevention measure is disinfecting containers before planting and between uses. Whenever you are transferring seedlings to bigger pots or rotating plants, wash and disinfect trays and pots with a solution of 1 part household bleach to 9 parts water.
I have also experimented with food grade hydrogen peroxide, which is a 35% solution that is intended for preparing food. However, I have found that this solution has not been as effective in preventing mold growth over long term use. If all else fails, you’ll have to throw out the plant because powdery mildew is very contagious.
Best indoor tomato varieties and care
When growing tomatoes, plant them as described above, not turning on the light until they have their first true leaves and watering them regularly to keep them moist. Use a small-space variety such as Pixie, Patio, Toy Boy, Small Fry, Tiny Tim, or Better Bush. These are some of the best vegetables to grow indoors in winter.
Plant 1/4 inch deep every two weeks so you’ll have a continuous supply. When they are around three inches tall, transplant into a 6″ pot with a tomato cage.
Now that your tomatoes are in their final home they will grow quickly. They can be fertilized two weeks after transplanting. When they start flowering, you will need to pollinate them by tapping the main stem and branches to encourage pollen to fall, and you can even use a paintbrush and recreate the actions of a bee flying from flower to flower.
While indeterminate tomato plants need to be pruned, determinate varieties like those named above produce all at once and don’t need pruning at all. Once they are done producing, pull out the plant and start again!
How to grow Swiss chard inside
Swiss chard is even simpler to grow indoors and will continue to grow all year with pruning. The example above was started from seed in mid-February. Once the leaves became a decent size, it was pruned every three to five days, always leaving three leaves on the plant. It has continued to grow for over eight months, even after being put outside during the summer.
To plant Swiss chard for indoor growing, soak the seeds overnight in a glass of warm water. Plant the seeds in a pot at least eight inches wide with soil and fertilizer mixed, and sow several seeds at least a few inches apart. Moisten the soil and keep it regularly watered, turning on the lights when the first true leaves appear.
Microgreens
If you’ve ever asked the question, “can you grow vegetables indoors in the winter?”, let me tell you about microgreens. No indoor growing primer would be complete without some information on the subject. All of the above details regarding temperature, water, sprouting and light apply, but microgreens are especially susceptible to mold, so the ventilation and disinfecting process should be strictly followed.
You will also need what are called ‘flats’, which are found at any garden supply store. The flats need to have drainage holes in them, so be sure to place something underneath to catch water.
Growing medium
You may also want to seriously consider growing microgreens in an alternative to soil. I have tried organic soil, potting mix and coco fiber mats. In my opinion, coco fiber, burlap or other fiber is definitely superior because it saves so much labor in cleaning the microgreens, which get covered in dirt when using soil.
When purchasing your seeds, you will need to keep track of the seed rates and learn to carefully spread them over the surface of your growing medium. You won’t need to cover them with soil, but you will need to keep them moist. To facilitate this, cover them with another flat by setting one flat inside the other—to keep them dark and damp until they begin to sprout. You can even weigh the flat down with a book to mimic weight of the soil.
Best microgreens varieties and care
Almost anything can be grown as a microgreens, with mixtures now being sold that create a tasty topping, such as basil, kale, mustard, peas, radish, arugula and spinach. You will need to feed your microgreens approximately once a week with some kind of water soluble nutrients. I like worm castings and liquid kelp as simple organic options.
Harvesting and cleaning
Microgreens are ready to harvest when the true leaves appear, but you can choose to let them grow a bit longer, to a maximum of about five inches. Cut them off carefully with sharp scissors, which can be done by holding the flat almost vertical and giving it a haircut. Then dump in a tub or sink of very cold water. Microgreens can’t sit in the water for long or they will become waterlogged, so agitate gently and drain, removing as much water as possible (a salad spinner works well). Bag and refrigerate immediately.
A complete microgreen cycle will take approximately 8-14 days including growing time and daily labor. This makes microgreens very time consuming, especially the disinfecting process. However, allowing the plants to grow up to five inches makes a lot of sense when you want to decrease your overall labor. Just be sure to include a slightly more dedicated feeding routine. For the dedicated home growers, microgreens are also quite important, because they provide some variety outside of the monotony of Swiss chard every day.
To sum up
Can you grow your veggies over the winter in your home? Yes you can! If you have had success with indoor vegetable plants, comment below!
