How to Grow Thyme Indoors on a Sunny Windowsill

By the Countertop Harvest team · Last updated October 20, 2026 · How we choose products

Thyme is a small, woody herb that does well on a bright counter as long as we treat it like the sun-loving Mediterranean plant it is. Penn State Extension lists thyme among the herbs that do best in direct sunlight (Penn State Extension), and Clemson's advice is full sun and very well-drained soil that stays dry (Clemson HGIC). Get those two things right and thyme is one of the least fussy herbs we grow. This guide covers light, pots and mix, watering, starting plants, harvesting and the problems we see most.

Light: as much as we can give it

Most herbs need around eight hours of direct light a day indoors, according to Iowa State Extension (Iowa State Extension). The University of Maryland suggests a south or west window with at least five hours of sun (UMD Extension). In practice that means the brightest sill in the house, and in winter it usually means a grow light as well.

Add a light in winter. Maryland runs grow lights or fluorescent lights 14 to 16 hours a day to make up for short winter days (UMD Extension). Iowa State keeps lights 6 to 12 inches from the leaves on a timer set for 12 to 16 hours (Iowa State Extension).
Watch for stretching. Penn State notes that herbs kept below their preferred light become thin and spindly, with smaller leaves and less aroma (Penn State Extension). Long gaps between leaf pairs on thyme are a sign to move it or add light.

If the kitchen is dim, our guide to how much light indoor herbs need explains how to measure a window, and grow lights under $50 covers small fixtures.

Pot and mix: small pot, sharp drainage

The RHS suggests a pot at least 6 inches wide and 4 inches deep for one thyme plant, with plenty of drainage holes, and mixes up to 25 percent grit into the compost to help it drain (RHS). Maryland's indoor mix is two parts soilless potting mix to one part perlite (UMD Extension), which gives a similar open texture. Iowa State likes clay or terracotta pots for herbs because they are porous and dry out more readily (Iowa State Extension), which suits thyme well.

Watering: let it dry a little

Thyme is one of the herbs that Penn State and Maryland both say should dry out between waterings (Penn State Extension; UMD Extension). We water thoroughly, let the extra run out of the drainage hole, then wait until the top of the mix feels dry before watering again. A saucer full of water is the quickest way to rot the roots, so we empty it after each watering.

Feeding is light. Penn State suggests a low dose of water-soluble fertilizer every 2 weeks (Penn State Extension), and Iowa State uses an all-purpose fertilizer at half or quarter strength (Iowa State Extension).

Temperature

Penn State recommends rooms of at least 65 to 70°F during the day and 55 to 60°F at night for indoor herbs (Penn State Extension). Maryland adds that herbs should be kept away from drafts and dry heat vents (UMD Extension). A sunny sill that gets cold at night is fine for thyme, but a sill above a radiator dries it out quickly.

Seeds, cuttings or a nursery plant

We usually start thyme from a small plant or a cutting. Illinois Extension says that while thyme can be grown from seed, it is much easier from divisions or cuttings (Illinois Extension). If you'd like to sow seed, the RHS says thyme germinates well at 59 to 68°F and should come up within a couple of weeks in a warm, bright spot (RHS). If you'd like a seed packet, here are English thyme seeds from Botanical Interests.

Harvesting and trimming

Because thyme is evergreen, the RHS says the leaves can be picked all year, and regular snipping keeps the plant compact and bushy (RHS). Iowa State's rule for perennial herbs such as thyme is to remove up to the top one-third of growth at a time (Iowa State Extension). We snip soft green tips and avoid cutting into bare wood, because the RHS warns that stems pruned hard into old wood may not reshoot (RHS).

Older plants get woody. Illinois says thyme should be renewed every few years by cutting it back hard in spring (Illinois Extension), while the RHS suggests it is usually best to replace old, straggly plants with new ones from cuttings (RHS). Our pruning guide shows where to cut on woody herbs.

To dry thyme, the RHS hangs sprigs in a warm, dark, well-ventilated place for a few weeks, then stores the leaves in an airtight jar (RHS).

Pets

The ASPCA lists thyme (Thymus vulgaris) as non-toxic to dogs, cats and horses (ASPCA). That doesn't mean a cat should graze on it, but it is one of the safer herbs to keep on a counter in a home with pets.

Common problems

Leggy, sparse stems

This is almost always light. Move the pot to the sunniest window or add a grow light on a timer, then trim the stretched tips so new, tighter growth can fill in. Our guide to leggy indoor herbs goes into more detail.

Gray, wilting or dying stems

Soggy mix is the usual cause indoors. The RHS says thyme is usually trouble-free in a warm, sunny spot with free-draining compost (RHS), so we check that the pot drains, let it dry out, and repot into a grittier mix if it stays wet.

Pests

Iowa State names spider mites as a significant pest for several herbs grown indoors (Iowa State Extension), so we check our thyme leaves now and then. Our indoor pest control guide covers what to look for and how to deal with it.

More herbs that like the same dry, sunny spot: rosemary, oregano and sage. You can also find a guide by plant.

Sources

All sources accessed October 20, 2026. This guide is about growing thyme as a kitchen herb.

Frequently asked questions

How much sun does thyme need indoors?

As much as you can give it. Iowa State Extension says most indoor herbs need around eight hours of direct light a day, and the University of Maryland suggests a south or west window with at least five hours of sun. In winter, add a grow light for 12 to 16 hours a day.

How often should I water indoor thyme?

Water thoroughly, then let the mix dry out a little before watering again. Penn State and Maryland Extension both list thyme among the herbs that should dry slightly between waterings. Empty the saucer so the pot never sits in water.

Is it better to grow thyme from seed or cuttings?

Cuttings or a small plant are easier. Illinois Extension says thyme can be grown from seed but is much easier from divisions or cuttings. If you sow seed, the RHS says it germinates well at 59 to 68°F within a couple of weeks.

How much thyme can I harvest at once?

Iowa State Extension suggests removing no more than the top one-third of growth on perennial herbs such as thyme. Snip soft tips rather than cutting into bare wood, which the RHS warns may not regrow.

Is thyme safe for cats and dogs?

The ASPCA lists thyme (Thymus vulgaris) as non-toxic to dogs, cats and horses.