How to Grow Herbs Indoors | Sunny Windowsill Success

Growing herbs indoors requires six to eight hours of strong daily light, fast-draining potting mix, containers with drainage holes, and watering only when the top inch of soil dries out.

For the full breakdown, see our best Indoor Herb Grower guide.

Fresh basil, rosemary, or mint from a kitchen windowsill is one of the simplest gardening wins a home grower can pull off. But moving outdoor herbs inside shifts the rules: light is weaker, pots hold moisture longer, and airflow drops. Get those three things right and the rest clicks into place. Here is the exact indoor setup that works, from window choice through harvest.

Light: The Make-Or-Break Factor

Most culinary herbs need roughly six to eight hours of direct sunlight each day to grow stocky and flavorful. A south-facing window is the best indoor spot; east or west windows can work if the light hits hard and unobstructed. Iowa State Extension says most herbs need about eight hours of direct light daily indoors.

If your windows come up short—especially during winter months—grow lights close the gap. Iowa State recommends placing fluorescent or LED lights six to twelve inches from the leaf tops and running them twelve to sixteen hours a day. Two 40-watt cool white fluorescent bulbs positioned a few inches from the plants supply enough intensity, and the 12-to-16-hour daily cycle mimics high-summer day length. Without enough light, herbs get leggy, pale, and weak-stemmed within a week or two.

Soil, Containers, and Watering: The Root-Zone Rules

Indoor herbs need light, fast-draining potting mix—never garden soil, which compacts in pots and drowns roots. Use a container-specific or soilless potting mix (peat- or coir-based) that stays airy even when moist. Pots must have drainage holes; set them in a saucer or drip tray to catch runoff, and empty the tray after watering so roots never sit in water.

Water only when the soil surface feels dry to the touch. For drought-tolerant herbs like oregano, sage, and thyme, let the soil dry slightly deeper before watering again. Basil, chives, mint, and parsley prefer slightly moister soil but still need the surface to dry between drinks. The practical cue: stick a finger into the potting mix—if the top inch is dry, water thoroughly until it runs from the drainage hole; if still damp, wait. Overwatering in low-light indoor conditions is the single biggest failure, especially in pots that are too large. Iowa State Extension notes that oversized containers stay wet too long for most herbs, so choose a pot just big enough for the plant’s current root ball.

If you’re starting from seed rather than nursery transplants, a 4-inch-deep container with drainage and a pre-moistened seed-starting mix (wrung-out sponge consistency) works well. Plant seeds at about twice their thickness beneath the surface, keep the mix evenly moist during germination (10 to 14 days), and remove the plastic cover once sprouts appear. Illinois Extension suggests monitoring for mold under the cover and improving airflow if you see any.

Temperature, Humidity, and Air Movement

Most herbs prefer indoor temperatures around 65–75°F during the day, with slightly cooler nights (55–60°F works well for many types). Keep pots away from cold window glass in winter and away from hot glass that can scorch leaves in summer. Good air circulation matters: crowded plants invite disease and grow weakly. If your room feels stagnant, a small fan on low speed (not pointed directly at the plants) helps strengthen stems and keeps foliage dry.

Indoor humidity drops low in winter. Counteract dry air by misting a couple of times a week or setting pots on a pebble tray with water below the pot base. Grouping herbs together also boosts local humidity naturally.

Fertilizer, Pruning, and Harvest

Herbs need light feeding, not heavy doses. Iowa State recommends an all-purpose fertilizer at half or quarter strength from early spring through summer, skipping winter applications. A premium potting mix may supply enough nutrients for the first couple of months, after which a fortnightly diluted liquid feed or a monthly slow-release organic fertilizer keeps plants productive.

Harvest once plants reach about six to eight inches tall. Snip stems just above a leaf node (the spot where leaves join the stem) to encourage bushy regrowth, and never remove more than one-third of the plant at one time. Morning harvest captures the best flavor and oil content. Regular trimming keeps plants compact; if a herb gets leggy despite good light, cut it back more heavily to a set of healthy lower leaves. Rotate pots every few days so all sides get even light and herbs grow straight instead of leaning toward the window.

FAQs

How often should I water indoor herbs?

Water only when the top inch of soil feels dry. For drought-tolerant types like rosemary and thyme, let the soil dry a bit deeper. For moisture-lovers like basil and mint, water when the surface dries but before the pot goes light. Always empty the saucer afterward.

Can I grow different herbs in one pot?

It’s hard to make one pot work because herbs have different water and root-space needs. Mint overtakes everything if potted together, and pairing a thirsty basil with a dry-soil rosemary usually leaves one unhappy. Iowa State Extension recommends separate containers for best results.

Why are my indoor herbs getting leggy?

Leggy, stretched stems are almost always a light problem. Move the pot to a brighter window or add grow lights positioned six to twelve inches from the leaves and running twelve to sixteen hours daily. Pinch back the tops to encourage bushier growth once light improves.