In colder climates, fall is the time when many gardeners begin harvesting and preserving their outdoor herbs to keep through the winter. But most dried herbs are not nearly as delicious as fresh herbs, so why not consider planting pots of your favorite herbs to grow indoors during the cold months? Fresh herbs improve even the best chef's cooking, and it's easier than you think to have all the flavor of an herb garden right on your windowsill.
Most herbs are rather well suited to the slightly cooler indoor temperatures common in winter. The challenge will be providing them with enough light and keeping the humidity levels optimal. If you meet the challenge, though, you'll have a never-ending supply of fresh herbs.
When to Plant an Indoor Herb Garden
It's quite easy to start an indoor herb garden by rooting cuttings from your outdoor plants starting in fall, as the weather cools. If you choose to sow your indoor herb garden from purchased seeds, most people begin a few weeks before the expected first frost of the season. With most herbs, you can begin snipping them for harvest within just a few weeks, so there's no reason to plant too far in advance.
Before Getting Started
There is considerable disagreement over what herbs are best suited for planting indoors. Some misinformation is spread by sellers of prepackaged herb gardens, who would like you to believe that just about any herb can be grown in their kits. But the reality is that not all herbs are well suited for growing indoors. Those with a woody, bushy growth, such as standard rosemary, are simply too big and ungainly to be well suited for indoors. But there are many herbs that are widely acknowledged as good choices for indoor growing, including chives, oregano, thyme, dill, mint, basil, coriander, sage, and creeping savory. These herbs are easy enough to grow that they are often recommended for indoor growing as school science projects.
Each herb has unique growing needs, however, so make sure to do a little research to make sure you have the light, humidity, and air circulation conditions the plant requires. And there's no point in devoting a lot of space to herbs you aren't likely to use very much—just because you can grow a plant doesn't mean you should. Instead, reserve your window space to grow ample quantities of the herbs that you use most often in cooking.
Equipment / Tools
- Garden trowel
- Plant grow lights (as needed)
- Potting soil
- Planting pots
- Pot trays
- Herb seedlings (as desired)
Choose a Location
An indoor herb garden will thrive if you can give it a sunny location (or comparable artificial light), and conditions that are coolish with slightly elevated humidity and good air circulation.
The best location will offer at least 6 hours of sun in a west- or south-facing window. If growing herbs under grow lights, they will need more light—14 to 16 hours a day under fluorescent bulbs placed about 6 to 12 inches above the plant. Because artificial lights lack the intensity of natural sunlight, the plants will require longer exposure to receive adequate light energy.
Ideal temperatures for herbs are 65 to 70 degrees Fahrenheit during the day, with nighttime temps no lower than 55 to 60 degrees. Don't put your herb pots near radiators or heat ducts, as they can quickly overheat and dry out. Herbs grow best in a location where there is good air circulation, but not harsh drafts.
Choose and Prepare Pots
Growing any herb in a container garden means taking special care to choose and prepare the proper pot. Herbs are fast-growing and can fill a pot with roots in less than one growing season, so it's best to choose good, large containers that are deep enough to accommodate the root growth. Choose pots that can drain well. When roots begin emerging through the drainage holes, it will be time to repot the herbs.
A standard commercial potting soil works well for most herbs. Herbs with a more tropical heritage (such as thyme and oregano) often prefer a more porous mixture, such as a blend of cactus potting mix and standard potting mix. Fill the container with potting mix to about 1/2 inch of the top. This will allow for some settling and leave room for watering.
Plant the Herbs
Plant your herb seeds, or transplant your herb plants, and water thoroughly. Allow draining until the pot no longer drips, then place on the windowsill or under grow lights with a tray underneath to catch any dripping water.
If the indoor air is especially dry—which is often the case in regions with cold winters—set the herb pots on trays of stones. Fill the trays with water, but keep the level below the drainage holes on the pots.
Tend Your Garden
Most herbs need regular water, but the soil should be allowed to dry out just slightly before watering again. Like most potted plants, indoor herbs require a bit more feeding than they would if planted in the outdoor garden. Give your indoor herb garden a dose of water-soluble fertilizer every two weeks or so. Keep the fertilizer fairly well diluted, as too much food will compromise the taste of the herbs. Turn the pots regularly to provide even sunlight and keep them growing evenly.
Observe your herb garden closely. All plants take on a different appearance when they are under stress and need water. Know how your plants look when they are healthy, and you will notice issues before they become larger problems.
Harvest as Needed
With most herbs, you can begin snipping them for harvest when they are just a few inches tall. Pruning back the herbs often means a larger, longer harvest. Try to cut the new growth back at least once a week, even if you are not using the herbs in recipes. Long stems that are about to set flower buds should be trimmed off as they appear.
Move Your Herb Garden Outdoors
Though not mandatory, many people like to move their potted herbs to an outdoor location on the patio or deck when the weather warms in the spring. They almost always enjoy the boost of sun they receive from a few months outdoors.
Some herbs can last for years rotating between outdoor and indoor growing locations, but with others, you will likely need to remove the plants as stems get woody and thick, replacing them with new seeds or seedlings. The organic material in potting mix (usually peat moss) breaks down after a while, which will require adding more potting mix or repotting the plants entirely.