When outdoor garden space is limited, or the weather outside is too cold, your windowsill can serve as a small-space garden for certain edible plants, such as leafy greens and herbs. Typical indoor temperatures are perfect for growing many types of food year-round. The key to successfully growing plants indoors is providing the right amount of light. With the right light, you can grow an indoor garden any time of the year.
How to Grow Leafy Greens & Herbs Indoors
Leafy greens such as lettuce, spinach, microgreens and kale can grow with moderate light, like what they'd receive in a part-shade/part-sun location in the outdoor garden. The same is true for cool-season herbs such as cilantro and parsley. Most of these plants are compact and so lend themselves to small-space kitchen gardening. If you have a bright south- or east-facing window, these vegetables and herbs are good candidates for windowsill gardening:
- Lettuce (loose leaf, butter, romaine)
- Mixed microgreens
Step 1: Start with Transplants
To plant your windowsill garden, start by picking up transplants of leafy greens and herbs at your local garden center. Look for loose-leaf lettuces, sorrel, arugula, spinach, kale, cilantro, parsley and related varieties, growing in 3- to 4-inch diameter pots.
Step 2: Pot Up Your Plants
Next, pot up each plant into a 6- to 8-inch diameter container, in a loose indoor potting mix, and place them in a bright windowsill or bright sunny room. A bigger pot will allow your plants to put down new roots. Choose pots with drainage holes and use a water-catching tray. Water your plants so that the soil is damp to the touch, but not soggy.
Step 3: Provide a Good Light Source
Place plants in a bright south-, east- or west-facing window. If you don't have a bright windowsill, you can also grow leafy greens, herbs and microgreens under low-intensity grow lamps. Two HO T5 fluorescent (HO stands for high-output, and T5 is the size of fluorescent grow lamp) or LED lamps will do the trick. Leave the lights on for 12 hours a day.
Step 4: Fertilize Monthly
Leafy greens and herbs aren't heavy feeders, but since you'll be harvesting from them regularly, be sure to feed them monthly with an organic natural liquid fertilizer that contains humus or seaweed.
Step 5: Harvest
If you start with transplants, you'll be able to start harvesting a few leaves from your potted leafy greens and herbs right away. If you're starting plants from seed, refer to the days-to-harvest listed on the seed pack. When harvesting, always snip off leaves growing around the outside of the plant, allowing the new leaves to continue growing from the center.
Leafy greens and herbs can be grown indoors continuously year-round, but if you're harvesting regularly you may need to refresh your plants with new ones from time to time.
Related: Easy Foods to Grow Without a Garden
Growing Microgreens Indoors
You can also grow microgreens in shallow trays or watertight bowls on a windowsill. Spread about 1 inch of a lightweight potting soil in a shallow watertight container. Sprinkle on a mixed microgreens seed mix, then water and cover with clear plastic or a humidity dome. Place the container by a bright window, and in a few days your microgreens will begin growing. Use kitchen scissors or small snips to harvest them just above the soil level, after they have developed their first set of new true leaves (true leaves look like miniature versions of mature leaves). Sprinkle in salads or soups.
Related: How to Grow Microgreens
How to Grow Fruiting Crops & Warm-Season Herbs Indoors
If your sights are set on root or fruiting plants, such as beets, tomatoes, peppers or beans—or sun-loving warm-season herbs such as rosemary and basil—the typical windowsill won't quite do the job. Plants expend a lot of energy producing storage roots and fruits. Sun-loving herbs won't keep growing without enough light; you'll need to add supplemental grow-lighting to provide enough energy for these crops.
- Bush beans
Step 1: Start with the Right Plants
Pick up 3- to 4-inch potted transplants of vegetables at your local garden center. Rooting and fruiting plants typically get larger than their leafy counterparts, so select dwarf varieties for indoor growing. Look for patio tomatoes and peppers. Bush beans, cucumbers, mini-beets, carrots and radishes can also be planted by seed directly into your pots.
Step 2: Plant in Large Containers
Plant into 1-gallon to 3-gallon containers in a loose indoor potting mix. Choose pots with drainage holes and use a water-catching tray. Water your plants so that the soil is damp to the touch, but not soggy.
Step 3: Add Supplemental Light
To grow rooting or fruiting crops choose a bright south- or west-facing windowsill, then place plants on a shelf that can support a light fixture with at least two HO T5 fluorescent or LED lamps. Metal kitchen shelving works well for this purpose. Grow lamps should hang about 12 inches above the plants. You'll need both the window light and supplemental light for good results. If you want to grow these edibles away from natural light (for example, in a grow-tent), double the amount of grow lamps, or use HID (high-intensity discharge lighting) grow lamps. Leave the lighting on for 14 hours a day.
Step 4: Fertilize Twice a Month
Fruiting crops are heavier feeders, so fertilize twice monthly with an organic liquid vegetable fertilizer.
Step 5: Harvest
Harvest when roots or fruits have reached mature size. You can refer to the days-to-harvest on the plant tag or seed packet for best timing. Fruiting and rooting crops can be grown indoors year-round. Once you've finished harvesting, start new plants.
Learning to grow food indoors is an exciting adventure. Keep in mind that every home has different ambient light conditions. The exposure of your window, as well as the season, will impact how much light you have and which crops you can grow.