Quick answer: Soak wheat, oat or barley seed for 8 to 12 hours, sow it thickly on 3 to 4 cm of moist compost in a shallow tray with drainage, cover loosely for two or three days, then give it bright light. Offer it at 10 to 15 cm, usually after 10 to 14 days, and sow a second tray a week later.
Many indoor cats like to chew grass. Giving them a tray of their own is safer than leaving them to nibble houseplants, some of which are toxic. Cat grass is simply young cereal grass, and it grows quickly on a windowsill.
This guide covers growing it reliably, without mould or mess. For safe plants more widely, see our cat-safe plants and indoor garden hub.
What Cat Grass Is
Cat grass is not a single plant. It is usually wheat, oat, barley or rye, grown from seed and cut or chewed while young and soft. It is different from catnip, which is a herb in the mint family. Wheat and oat are the easiest to find and grow.
Choosing Seed
Buy seed sold for sprouting or for cat grass, which is untreated. Avoid seed sold for farming or lawns, which may be coated with fungicides or other chemicals. A 250 g bag sows several trays.
| Seed | Sprouting | Height at 10 days | Notes |
|---|---|---|---|
| Wheat | 2 to 3 days | About 12 cm | Fast and widely sold |
| Oat | 3 to 4 days | About 10 cm | Softer blades, popular with cats |
| Barley | 2 to 4 days | About 12 cm | Hardy, slightly coarser |
Times vary with temperature; a room at about 20 degrees gives the figures above.
Choosing the Tray
Use a shallow tray about 5 to 8 cm deep, with drainage holes and a saucer underneath. A heavy ceramic or wooden tray is harder for a cat to tip than a light plastic pot. A tray of about 15 x 25 cm gives a good patch for one cat.
Soaking the Seed
Soak the seed in cool water for 8 to 12 hours, then drain and rinse it. Soaking speeds up sprouting and gives a more even crop. Do not soak for more than about 12 hours, since waterlogged seed can start to rot. Rinse until the water runs clear.
Sowing
- Fill the tray with 3 to 4 cm of moist, peat-free multipurpose compost or coir.
- Scatter the soaked seed thickly in a single layer, so seeds almost touch.
- Press the seed gently into the surface; do not bury it deeply.
- Cover loosely with a damp cloth or a lid with a gap for air.
- Keep it at room temperature out of direct sun.
Avoid compost with added fertiliser pellets or wetting agents, which a cat may chew.
A Day-by-Day Timeline
| Day | What happens | What to do |
|---|---|---|
| 0 | Soak seed | 8 to 12 hours, then rinse |
| 1 | Sow and cover | Keep damp, not wet |
| 2 to 4 | Roots and shoots appear | Remove cover once shoots show |
| 5 to 9 | Rapid growth | Bright light, water from below |
| 10 to 14 | 10 to 15 cm tall | Offer to the cat |
| 14 to 21 | Peak use | Trim tips, start next tray |
| 21 onwards | Yellowing, flopping | Compost and resow |
Watering Without Mould
Mould is the most common problem with cat grass. It shows as white fuzz on seeds or soil, and it smells musty. Prevent it by keeping the compost damp but never soggy, watering from below by filling the saucer and tipping away what is not absorbed after 30 minutes, and removing the cover as soon as shoots appear. Good airflow helps.
Do not confuse fine white root hairs, which are normal, with fuzzy mould on the surface. If mould appears, discard the tray and start again with fewer seeds. The EPA brief guide to mold and moisture explains why damp indoor surfaces need care.
Light
Once shoots appear, move the tray to the brightest window you have. Grass grown in low light turns pale, thin and floppy. Turn the tray every two days so it grows evenly. Avoid a sill above a radiator, which dries the compost too fast.
When to Offer It
Offer the grass when it is 10 to 15 cm tall and the blades are bright green and firm, usually after 10 to 14 days. Put the tray at floor level or on a low, stable spot where the cat already rests. Many cats chew it straight away; others take a few days.
Trimming and Lifespan
Trim the tips with scissors if the grass gets long and floppy, and give the cut tips to the cat. A tray stays useful for about one to two weeks after it is ready. When the blades turn yellow or start to fall over, compost the whole tray and resow.
A Two-Tray Rotation
For a steady supply, sow a second tray about seven days after the first. By the time the first tray is past its best, the second is ready. Keep a jar of seed and a bag of compost together to make resowing a two-minute job.
Is Eating Grass Safe?
Most cats chew a little grass without problems. Some vomit afterwards, which is common and usually brings up hair or grass. Frequent vomiting, vomiting with other signs such as not eating or lethargy, or a sudden increase in grass eating is worth discussing with a vet. Our guide to preventing hairballs covers grooming and diet.
Keeping Toxic Plants Away
A grass tray does not make toxic houseplants safe. Cats that like chewing greenery may still try others. Lilies are particularly dangerous to cats. Our cat-safe houseplants list and our guide to safe lookalikes help you choose plants. In winter, our guide to holiday plants covers seasonal risks.
If your cat chews a plant you are unsure about, call your vet or ASPCA Animal Poison Control. The FDA on lilies and cats explains why lilies are so dangerous.
Where to Put the Tray
Cats tend to chew grass when they are relaxed, often after waking or after a meal. Put the tray near a favourite resting spot or a window perch, not beside the litter box or food bowls. A tray on a sill the cat already uses gets the light it needs and stays in the cat's routine. Our window perch hub has ideas for a sill-level platform.
Keep it away from the walkway, where it can be kicked, and off soft furnishings, where a spilled saucer leaves a stain. In a small home, a low plant stand beside the sofa works well.
Cat Grass in Winter
Short days and cooler rooms slow growth. In winter, expect 14 to 18 days to reach full height, and choose the brightest, warmest window. Rooms below about 15 degrees may give patchy results. A small LED grow light on a timer for 12 hours a day helps on a dark sill. Our seasonal DIY projects covers other winter jobs.
Indoor heating dries compost quickly, so check the saucer daily.
Keeping the Tray Tidy
Some cats dig in the compost or tip the tray. A heavier tray, a lid of chicken wire pressed just above the soil before sowing, or a ring of stones on the surface all help. Wipe the saucer weekly so stale water does not smell.
Growing Without Compost
Grass can also be grown on a damp paper towel or a sprouting mat in a shallow dish. This is cleaner, but trays dry out faster and need checking twice a day. Rinse the mat between crops to avoid mould.
Cat Grass Growing Questions
How long does cat grass take to grow?
Usually 10 to 14 days from sowing to a height of 10 to 15 cm at about 20 degrees. Soak the seed for 8 to 12 hours first, sow it thickly, cover it for two or three days, then move it to bright light once shoots appear.
Why is my cat grass going mouldy?
Usually because the compost is too wet, the seed was soaked too long or the cover stayed on too long. Water from below, tip away excess after 30 minutes, remove the cover once shoots show and keep air moving. Discard a mouldy tray and resow.
What seeds should I use for cat grass?
Wheat, oat or barley seed sold for sprouting or as cat grass, which is untreated. Avoid farm or lawn seed, which may be coated with chemicals. Wheat grows fastest; oat gives softer blades many cats prefer. A 250 g bag is enough for several trays.
Is it normal for my cat to vomit after eating grass?
Occasional vomiting after chewing grass is common and often brings up hair. Frequent vomiting, vomiting with not eating or lethargy, or a sudden increase in grass eating is worth checking with a vet. A grass tray should never replace advice about ongoing stomach upsets.
How often should I replace cat grass?
A tray is useful for one to two weeks after it reaches 10 to 15 cm. When blades yellow or fall over, compost it and resow. Starting a second tray about seven days after the first keeps a fresh supply ready.
