Windowsill Herb Garden: Grow Herbs in a Window Year-Round

How to Start a Windowsill Herb Garden

A windowsill herb garden works when three things line up: a south or west window that gets about six hours of direct sun, pots of 4 or 5 inches with drainage holes, and herbs that suit indoor life. Start with parsley, chives, mint, thyme, oregano and basil in separate pots of soilless potting mix. Water when the top inch is dry, and pick no more than a third of a plant at a time. In winter, add a grow light and keep basil away from cold glass. That routine keeps a window full of herbs through all four seasons.

Setting one up takes an afternoon:

1. Choose the window. South is best, and bright west or east exposures can work.
2. Pick small pots with drainage holes and saucers. Iowa State University Extension recommends clay or terracotta.
3. Fill them with a soilless potting mix. University of Maryland Extension suggests two parts mix to one part perlite for extra drainage.
4. Plant one kind of herb per pot, so each can be watered the way it likes.
5. Water thoroughly with room-temperature water and empty the saucers.
6. Wait until plants are 6 inches tall before the first harvest.

If your window gets little direct sun, a self-contained indoor herb garden kit with its own light may serve you better than a bare sill.

The Best Herbs for a Window

Iowa State University Extension lists parsley, mint, chives, basil, oregano, cilantro and thyme as the herbs that grow best indoors, with rosemary, sage, lemon balm, marjoram, chervil and bay as further options. They do not all want the same seat on the sill.

Herb	Light	Watering	Notes
Chives	Tolerates 2 to 6 hours of direct sun	Water when the top inch is dry	Suits a dimmer window
Cilantro	Tolerates 2 to 6 hours	Water when the top inch is dry	Annual, so it can be cut back hard
Lemon balm	Tolerates 2 to 6 hours	Water when the top inch is dry	Handles a less sunny sill
Parsley	About 6 hours	Water when the top inch is dry	On Iowa State’s best-indoors list
Mint	About 6 hours	Water when the top inch is dry	Keep in its own pot
Basil	About 6 hours, warm	Never let it dry out completely	Cannot survive below 50°F
Thyme, rosemary, bay	About 6 hours	Let dry slightly between waterings	Take the top third when harvesting
Oregano, sage, marjoram	About 6 hours	Let dry slightly between waterings	Take the top third when harvesting

Avoid herbs with large root systems, such as fennel and lovage, and give taprooted dill a deep pot. Cilantro has its own quirks indoors, covered in how to grow cilantro without bolting.

A note on grocery-store pots. University of New Hampshire Extension points out that supermarket herbs are planted too densely, with a dozen or more seedlings in a pot large enough for one healthy plant. To keep them for more than a few weeks, thin them or divide the clump into several containers.

How Much Light Window Herbs Need

Light is the limit for nearly every indoor herb. Extension recommendations cluster in a narrow band: Maryland says at least five hours of sun a day in a south or west window, Penn State and New Hampshire say a minimum of six hours of direct sunlight, and Iowa State says most herbs need around eight hours for good growth indoors. Chives, cilantro and lemon balm are the exceptions that tolerate 2 to 6 hours.

A south-facing window delivers the most. Bright east or west windows can be good as well. Rotate the pots regularly so plants grow evenly and do not lean toward the glass.

When the window falls short, which is common from late fall through winter, add a lamp. Penn State and New Hampshire both recommend 14 to 16 hours a day under lights, and Iowa State gives a range of 12 to 16 hours on a timer. Position the light 6 to 12 inches above the leaves. Our guide to grow lights for herbs indoors in winter compares the types that fit a sill.

Watering Herbs in a Windowsill Pot

New Hampshire Extension calls overwatering the number one reason herbs do not last indoors. The fix is to check before you pour. Water only when the top inch of mix is dry, then water enough that it flows freely from the bottom of the pot.

The herbs sort into two groups. Bay, marjoram, oregano, sage, thyme and rosemary should dry out slightly between waterings. Basil is the opposite and should never be allowed to dry completely. For parsley, mint, chives and cilantro, the top-inch test is the guide.

Pot size matters here more than people expect. Iowa State warns that containers that are too large stay wet too long, and Kansas State’s guidance for indoor herbs is a 4 or 5 inch pot. Small pots dry on a predictable rhythm, which makes the finger test reliable. In cooler weather, when growth slows, water less often.

If basil leaves turn yellow, why basil turns yellow walks through the causes.

Temperature, Humidity and Airflow on the Sill

Herbs like the temperatures people do. Penn State gives the target as at least 65 to 70°F during the day and 55 to 60°F at night, and New Hampshire states the daytime range as 65 to 75°F. A sill that cools off after dark suits most herbs well.

Basil is the exception. It cannot survive temperatures below 50°F, and Penn State advises against keeping it on a windowsill in the winter months, when the air beside the glass can be far colder than the room. Move basil to a table under a light for the coldest part of the year.

Two other hazards sit near windows. Keep pots away from drafts and from dry heat vents, as Maryland advises, since both stress plants quickly. Heated air is also dry, so group the pots together or stand them on a tray of moistened pebbles to raise humidity around the leaves. Kansas State notes that a small fan promotes sturdier stems and can disrupt insect pests.

Feeding and Repotting

Potted herbs need only light feeding. Iowa State recommends periodic light feeding with an all-purpose fertilizer solution at half or quarter strength, from early spring through summer. Penn State’s version is a low dose of water-soluble fertilizer every 2 weeks. Stop or cut back in the darkest months, when the plants are barely growing.

Repot when roots come out of the drainage hole. Early spring is the best time, because the plant is about to grow quickly and will fill the new mix. Keep the new pot modest, since oversized containers stay wet too long.

Harvesting So Plants Keep Growing

Regular picking keeps herbs compact and productive. Two rules from extension sources cover most of it: wait until a plant is 6 inches tall, and remove no more than a third of it at a time.

For perennial herbs such as thyme, oregano, sage and mint, Iowa State’s guidance is to remove the top one-third of the growth. Annual herbs such as basil and cilantro can be cut back harder, leaving approximately 4 to 6 inches of stem to regrow. On basil, cut just above a pair of leaves so the plant branches, as shown in how to pinch basil. A pair of herb scissors makes clean cuts on soft stems.

A Year-Round Routine

The same sill behaves differently in January and July, and the care shifts with it.

• Spring: repot rootbound plants in early spring and begin light feeding. Resow cilantro and basil.
• Summer: growth peaks, so check moisture often and harvest weekly. When outdoor temperatures stay above 50°F, pots can spend time outside if you introduce them to full sun gradually, starting in partial shade.
• Fall: bring pots back in before nights fall below 50°F. Tender perennials such as rosemary and bay can winter on the sill, as described in overwintering rosemary and bay.
• Winter: run a grow light 14 to 16 hours a day, water less often, stop feeding, and move basil off the cold sill.

Common Windowsill Problems

Thin, spindly growth with small leaves and weak aroma means too little light, and a lamp is the remedy. For fungus gnats, the small flies around the soil, Penn State’s advice is yellow sticky traps near the plants and proper watering. See how to get rid of fungus gnats for a full plan. For insects such as aphids, Penn State’s first step is to trim off infested branches and put them in the trash. It reserves soft insecticides for extreme cases, used according to the label, because herbs are eaten fresh.

Quick Recap

• Use a south or west window with about 6 hours of direct sun, and add a light for 14 to 16 hours a day when the sun is weak.
• Grow each herb in its own 4 or 5 inch pot with drainage, and water when the top inch is dry.
• Keep days at 65 to 75°F and nights at 55 to 60°F, with basil always above 50°F.
• Feed at half or quarter strength from early spring through summer.
• Harvest once plants reach 6 inches, taking no more than a third.