Be aware that garlic and other onion family members are toxic to dogs and cats. Toxicity is more pronounced in the bulbs, but the leaves are also toxic to pets. It’s not advisable to grow it indoors if you have pets that nibble on your houseplants. If you want to grow actual bulbs, you’ll need to first chill the bulbs in the refrigerator or another cold location for several weeks before planting. Like many perennial bulbs, garlic—especially the hardneck varieties—must have this cold dormant period for the planted cloves to develop into mature bulbs. This chilling period is less crucial for softneck types, which will grow more successfully without the chilling period; softneck varieties are often preferred for indoor growing. Planted indoors in early fall after a chilling period of several weeks, you may have harvestable bulbs by early to late spring, provided you could give the plants plenty of sunlight. But if your goal is just green shoots to snip off for cooking, the chilling period is unnecessary. The green shoots should be large enough before you begin snipping them off for cooking.
How to Grow Garlic Indoors
Garlic bulbs are typically broken into cloves and planted in pots for indoor growing at the end of the outdoor gardening season, whenever that might occur in your region.
Sunlight
Growing garlic bulbs requires a lot of direct sunlight; they do not thrive with artificial light. If you want to develop full garlic bulbs, plant just one clove in each container, then place it in the sunniest location (usually a South-facing window) to get full sun all day. Garlic needs at least six hours of sun per day, which can be hard to achieve during the short days of winter. If you are growing garlic just for the greens, it won’t need quite as much sunlight.
Temperature and Humidity
Garlic can grow indoors all year long. Avoid sweltering temperatures or freezing temperatures for your indoor garlic. A range of 60 to 80 degrees Fahrenheit is ideal. Garlic is native to relatively arid regions of central Asia and Iran, so it thrives in dry conditions. There is no need to bolster humidity to grow indoor garlic.
Watering
Water garlic often enough so that the soil stays moist but not wet. Within one to two weeks, you should see green garlic shoots coming through the soil. Usually, garlic plants should get about 1 inch of water per week; however, with really fast-draining sandy soil, give up to 2 inches per week. The rule of thumb is not based on inches, but more based on touch—water the pot whenever the potting mix feels dry to the touch.
Fertilizer
If you are growing garlic for the bulbs, feed the plants twice a month with a water-soluble balanced fertilizer diluted to half strength. Feeding is not necessary for garlic that you are growing only for the greens.
Pruning and Maintenance
Wait until the shoots get a couple of inches tall before you start snipping them with scissors to use the greens for cooking. Leave about 1 inch of the green shoot on each clove so the shoot will continue to grow. If your aim is mature bulbs, be patient—garlic cloves take a long time to develop into bulbs for harvest. When the leaf shoots begin to turn brown, withhold all watering. Within a couple of weeks, the shoots will be entirely dried out, and the bulbs should be ready to harvest for cooking. If you wish, garlic bulbs can be stored in a dark, cool place for several months to be used as needed.
Container and Size
A simple clay pot at least 6 inches deep with a drainage hole in the bottom makes a suitable container for growing garlic, but other containers can also work. The width of the container depends on how many cloves you plant. If growing bulbs, plan to plant them at least 6 inches apart. If only growing greens, you can plant the cloves next to each other in a single pot. If you are using a can or another container without drainage, you will need to make holes so the water can get out. You can make several large holes with a drill. If you use a ceramic container that doesn’t already have drainage holes, you can drill drainage holes with a special ceramic bit. If you use a leftover metal can, such as a coffee can, you can bore drainage holes using a hammer and nail.
Potting Soil and Drainage
Garlic bulbs like well-draining soil and may rot if they’re left soaking in soggy soil. Do not use garden soil or purchased topsoil to grow garlic indoors; it will not drain well when confined in a container. Garlic thrives in loamy, sandy soils. You can also plant garlic in peat, perlite, vermiculite, coconut fiber, potting mix, or compost. The drainage holes in the bottom of the container need to be covered with a paper towel, a coffee filter, or a piece of plastic window screening to keep the soil in the container while allowing water to drain out freely.
Potting and Repotting Garlic
You can use any mature garlic bulb you’ve grown outdoors for indoor planting or purchased as a seed garlic bulb. Many growers recommend storing the bulbs in a refrigerator for a few weeks before planting them in the fall. Split the garlic bulb into cloves by prying it open. Keep as much of the skin on as possible, though it’s okay to brush off parts of the dry, papery husks. Discard any cloves that are soft or show signs of decay. Fill the container with a standard potting mix, so the surface is about 2 inches below the rim. Plant the cloves pointy-side-up in the container, embedding them halfway into the potting mix. Leave at least 6 inches between cloves if growing bulbs. You can plant the cloves close together for garlic greens, but don’t allow them to touch. Fill the container with more potting mix until it covers the garlic by about 1/2 inch, making sure to fill in all the spaces between the cloves. Pat the soil down gently. Water slowly until water comes out of the bottom of the container. Add more potting mix if you see any garlic cloves poking through.
Moving It Outside for the Summer
Considerations
Garlic is a sun lover, and it’s also a cold-hardy bulb outdoors. It is a USDA zone 4 hardy plant, meaning it can withstand temperatures as low as -30°F. It doesn’t love sweltering temperatures, and usually by July, when the green tops have browned, it’s time to harvest the bulbs. You can take an indoor-outdoor hybrid approach to growing your garlic, by bringing it outside once it’s already sprouting in your windowsill in the spring. Bringing it outdoors in the full sun will give it the extra kick it needs to grow the flower and bulb to full size. On sweltering days, you will need to give more water to sustain the plant through a hot spell.
When to Bring Garlic Back Inside
Garlic doesn’t have to be brought back inside since it can overwinter in the ground or containers just fine. It enters a dormancy state, but it triggers growth as soon as the temperatures warm. If you choose to have garlic greens throughout the winter, plant them at any time inside throughout the year. Or, if you bring your garlic inside during the summer, they’ll last until the sprouts start turning brown, indicating the bulb is mature and ready to harvest. To acclimate your garlic to life inside without shocking it, gradually, over two weeks, bring the plant in for two hours, then four the next day, then six, and so on. Before bringing your plants indoors, inspect them carefully for hitchhiking bugs. If you notice a few insects or a pest infestation, deal with the problem outside before bringing it indoors. Keep an eye out for onion thrips. Thrips have wings but are not great fliers. They look more like long worms with long legs. They can cause significant damage, but you can control them by washing the plants with water, planting sticky traps, treating them with neem oil or pyrethrin, or as a last resort, chemical pesticides.
