Cat Grass, How to Grow, Harvest, and Keep It Healthy Indoors

Messing up cat grass costs wasted seed, moldy trays, or a pot your cat walks past. Yes you can grow fresh cat grass in a pot in 7 to 10 days with the right seed, a shallow tray, good potting mix, and a dry top layer.

Choose the right seed, wheat berries, oats, barley, or a ready sprout mix

Not all “grass seed” will work. Lawn seed and seed treated for field planting often carry fungicide or weed control coatings that stop sprouting or make it unpleasant for pets. For reliable sprouting pick food grade wheat berries, hulled oats, or whole barley, or buy a labeled sprouting mix.

My go to seeds, what I use and why

• Wheat berries, organic, food grade, Bob’s Red Mill style, for even green blade and quick regrowth.
• Hulled oats, smaller and sweeter, good if your cat prefers softer shoots. Soak a little longer.
• Hulled barley, fast green and sturdy. I use it in mixes for longer first harvests.
• Ready sprout mix, from a sprouting seed supplier, when I want predictable germination and less sorting.

Buy seeds labeled edible, organic if possible, and avoid anything labeled “for planting” or “turf.” If you get poor germination, check the bag for any chemical treatment or buy a different brand.

Pick a container and soil, exact pot sizes, drainage, and quantities

Cat grass roots are shallow. Use shallow containers with good drainage. I keep a few sizes on hand for different needs, so I can plant this weekend no matter how much space I have.

Recommended container sizes, how many square inches each seed rate covers

• 4 inch round pot, top area about 13 square inches, good for one cat, use 1 tablespoon seed.
• 6 inch round pot, top area about 28 square inches, use 3 tablespoons seed.
• 8 by 8 inch square tray, 64 square inches, use 6 tablespoons or about 1/3 cup seed.
• 10 by 6 inch seed tray, 60 square inches, use 1/3 cup seed.

Containers should be 1.5 to 3 inches deep. Place at least one drainage hole and a matching saucer. Do not use sealed plastic without drainage. If the pot will sit on furniture, set the saucer on a small plate lined with a paper towel.

The potting mix recipe I use, and what to avoid, with cup and depth measurements

For a single 6 inch pot I mix 2 cups total potting mix. Recipe scales linearly.

• 1 cup coco coir or peat moss, hydrated
• 1/2 cup coarse perlite
• 1/2 cup screened compost or worm castings

Fill the 6 inch pot to 2 inches deep with this mix, leaving 1/4 inch to the rim to prevent overflow. For an 8 by 8 tray use 6 cups of the same mix to reach a 1 inch depth.

Avoid heavy garden soils, unsterilized manure, or moisture-locking mixes labeled “water retaining.” Those encourage mold and damping off. I lost a tray once to mold after using straight compost, so drainage and aeration matter.

Step by step sowing method you can follow today, soak, sow, cover, and light

Do this on a weekend morning. You can seed several pots in under 30 minutes.

Exact seed soaking times, sowing depth, seed rate per pot, and germination temperature

1. Measure seed. Use the rates above for your container size.
2. Soak seeds in cool water: wheat berries 6 hours, barley 6 to 8 hours, hulled oats 8 to 12 hours. Do not soak more than 12 hours or seeds will ferment.
3. Drain and rinse once after soaking, then let sit 30 minutes to drain fully.
4. Fill pots to desired depth with the mix. Moisten to a wrung-out sponge level. For a 6 inch pot that is about 1/4 cup of water mixed evenly into the 2 cups of mix.
5. Broadcast seed evenly. Press seeds lightly into the surface with your hand. Do not bury deeper than 1/8 to 1/4 inch. A dusting of 1/8 inch of potting mix or vermiculite is optional; I prefer a thin dry top layer of coarse perlite or sand to reduce surface mold.
6. Target soil temperature 68 to 75 degrees Fahrenheit for fastest germination. Warmer than 80 degrees can increase mold risk; cooler than 60 degrees slows germination to 10 to 14 days.
7. Place tray in bright, indirect light. Direct strong sun can bake the seedlings and dry the top layer too fast in summer.

Daily care for the first 7 to 10 days, watering method and signs to watch

• Watering method, first week: bottom water every other day by pouring 1/4 cup into the saucer for a 6 inch pot, 1/2 to 1 cup for an 8 by 8 tray. Let the soil soak up for 10 minutes, then discard excess. This keeps the surface slightly drier to reduce mold.
• Alternately, mist the surface twice daily for the first 3 to 4 days, then switch to bottom watering.
• Watch for white fuzzy mold on the surface, slimy seeds, or a sour smell. If you see that, increase airflow, lower temperature by a few degrees, remove the top 1/4 inch of mix, and reduce watering frequency.
• Seedlings should push up in 3 to 7 days and be 3 to 4 inches tall in 7 to 10 days under good conditions.

Common mistake, and how to avoid it. Overcrowding and keeping the top layer constantly wet leads to mold. I separate trays so air moves between them and I use the dry top layer trick.

Midsummer care, prevent heat stress, deep watering, and harvest timing

July heat changes how you water and where you place your pots. Indoor temperatures often rise above ideal. That stresses grass and invites mold.

How to keep cat grass cool indoors, when to move trays out of direct afternoon sun

• Move trays out of direct afternoon sun when indoor temperatures exceed 78 degrees Fahrenheit. Morning sun is fine. South windows that bake in July will scorch blades.
• Place pots on a tiled floor or a pebble tray to keep roots cooler by 2 to 4 degrees. A small fan on low provides air circulation and reduces fungal problems.
• If your home stays above 80 degrees, keep the tray in a cooler room such as a basement or in front of an open window at night when temperatures drop.

How and when to harvest so the cat gets the most nutrition and you get the longest run

1. First harvest at 3 to 4 inches tall. Use scissors to cut the blades about 1/2 inch above the soil. That leaves crowns for regrowth.
2. A typical sowing yields two to three harvests. After each harvest, water well, keep in bright light, and expect 7 to 14 days to regrow depending on temperature.
3. If blades yellow and slow regrowth after two cuts, remove old plants and reseed. Reseeding a small tray takes about 30 minutes and you can start a new pot while one is growing.
4. In midsummer you may harvest sooner because growth is faster, but watch for heat stress. If blades curl or brown at the tips, move to cooler spot and delay heavy harvesting until they recover.

One trick I use, especially when I will be away, is to stagger sowings. Start a new 6 inch pot every 7 to 10 days so fresh grass is always available.

For outdoor-sunlight lovers who place trays on a balcony, set trays in morning sun and shade in afternoon. If your last frost is late or your first fall frost is early where you live, remember these plants do best indoors year round. If you need help timing outdoor tasks for vegetables, see when to water vegetable plants in summer and adjust indoor watering similarly.

FAQ heading

Can I use wheatgrass seed sold at garden centers?

Maybe not. Garden center wheatgrass is sometimes treated for field planting. Buy food grade wheat berries or a labeled sprout mix. If the seed does not swell during a reliable soak it is likely treated. For more on common seed problems see common mistakes new gardeners make.

How often should I replace the soil or start a fresh tray?

Replace the soil after three harvests or when roots feel compacted. For a small pot that usually means two to three weeks. Compost and lightly freshen the mix if you want to reuse the container once, but when in doubt start with fresh mix for best results.

My cat prefers nibbling live leaves, can it eat the whole pot?

Yes, but prevent overgrazing. Offer two small pots and rotate them. If the cat eats the entire pot down to the crown, reseed immediately. Keep a fresh pot available to avoid overgrazing one tray.

What if I get mold on the trays after sowing?

Stop watering the surface, increase air movement, and remove the top one quarter inch of mix with mold. Switch to bottom watering and place the tray in brighter, indirect light. If mold recurs, start again with a thinner seed layer and a dry top surface.

I keep a small stack of trays and seed in my kitchen. It takes one weekend morning to set up a month of fresh greens for the cat. If you want a longer-lived windowsill herb garden alongside cat grass, see best herbs for small backyard gardens. If you prefer planting outside and worry about drainage, the same drainage principles apply as in raised bed gardening for beginners.

One last note on timing. In zone 6b central Ohio I sow indoors any time of year. If you live colder than zone 6b, keep trays indoors through first frost indoors and only move trays outside after your last spring frost. In warmer zones you may need to protect trays from midafternoon heat. Keep an eye on soil temperature, and you will have fresh cat grass in under two weeks.