Repotting Season: Soil Hazards a Cat Will Eat

Spring repotting puts 3 things on the floor that a cat investigates with its mouth: perlite, slow-release fertilizer prills and damp coir. None is a classic poison in the way lily pollen is, and all 3 cause real trouble in the 1-48 hours after a cat swallows them. The 48-hour rule near the end of this page removes most of the risk for the cost of one closed door.

What is actually in the bag

Most bagged potting mix runs 40-70% peat or coir, 10-30% perlite by volume, and a measured dose of slow-release prills, often 2-5 g per liter of mix. Perlite is expanded volcanic glass at 2-6 mm, light enough to float to the surface when you water; vermiculite is mica expanded into 3-8 mm flakes that hold water. Both are inert, so the danger is mechanical rather than chemical: 1-2 teaspoons of grit in a 4 kg cat can sit in the stomach for days or block the pylorus, and coarse perlite scratches on the way through.

Do the arithmetic before the bag is open. A 20 L bag dosed at the label's 2-5 g per liter carries 40-100 g of prills, and at roughly 0.02-0.03 g per 3-4 mm granule that is 1,500-3,800 individual pieces on your floor. That count is why a lidded bin matters more than a tidy floor.

Perlite and vermiculite: small, sharp, everywhere

A dropped 5 L bag spreads 200-500 g of mix over 1-2 m2, and a cat walking through it grooms off 20-40% of what sticks to its paws within the hour. The usual picture is mild: 1-3 vomits in the first 6 hours, some drooling, a cat that eats half its dinner and is normal by the next day. The exception is a cat that chews into the open bag, because dry granules swell slightly with saliva and can clump into a 2-3 cm ball that will not pass; persistent vomiting 6-12 hours later needs an X-ray, not another day of watching.

Slow-release fertilizer: the 3-4 mm problem

Prills are coated urea or NPK blends, commonly 14-14-14 or 18-6-12, with a release window of 3-9 months at 20-25 C. The coating is exactly what makes them risky to a cat: the prill is swallowed whole, the coat breaks down in the gut, and a dose meant to feed a plant for 90 days lands in 1-2 hours. Signs start 30-60 minutes to 6 hours after eating: drooling, 2-5 vomits, abdominal pain, and in severe cases tremors. Some blends carry organophosphates or disulfoton, which produce pinpoint pupils and weakness; that combination means a clinic in under 60 minutes.

Coir, fungus and the 48-hour quarantine

Coco coir arrives at pH 5.5-6.7 and holds 8-9 times its weight in water, so an open bag in a 20-25 C room becomes a warm damp block, which is a good place for mold. White fuzz on coir is usually a saprophytic fungus; the risk to a cat is not poisoning but inhaled spores, which matter most in a cat with asthma or a previous upper respiratory infection. Hence the 48-hour rule: repot, water, close the door for 48 hours, crack a window, and clean the floor with a damp cloth instead of a broom, which lifts the dust straight back into the air.

What to watch after contact

Write down the time, then check at 30 minutes, 2 hours, 6 hours, 24 hours and 48 hours: drooling, vomits counted, appetite, stool, urine output, and pupil size in a normally lit room. Most exposures produce nothing at all, and the 24-48 hour window is long enough to catch the ones that do. Photograph the bag, the label and a few prills on a white plate, since the NPK number and the product name are the first two things a poison line asks for.

Material	Particle size	Main risk	Onset	Action
Perlite	2-6 mm	Grit, blockage	6-12 h	Watch 24 h
Vermiculite	3-8 mm	Grit, swelling	6-24 h	Watch 48 h
Slow-release prills	3-4 mm	Fertilizer dose	30-60 min	Call at once
Coir with mold	Fuzz, dust	Spore inhale	24-72 h	Vet if coughing
Fresh mix dust	Under 1 mm	Eye, nose irritant	1-2 h	Rinse, ventilate

When it is a vet call, not a wait

Call within 30 minutes for any fertilizer prill eaten, more than 3 vomits in 2 hours, tremors, pinpoint pupils, or a cat that refuses food for 24 hours. Bring the bag and the plant tag. For inert perlite alone, 24-48 hours of home watching is reasonable if the cat keeps eating and passes stool normally. Keep the toxic plant list open while you unpack, because the soil is rarely the worst thing in the room: lily pollen, sago palm and azalea all outrank a mouthful of perlite.

Where the season hands you the problem

Repotting usually lands in the same 2-3 weeks as the first flea hatch and the spring shed, so a cat is already licking more than usual: spring fleas and allergies covers the itch side, and spring shedding explains why a hairball plus a mouthful of grit is a bad combination. Groom the cat before you open the bag, not after.

The 5-step repotting routine

• Repot in a closed room, on a 2 x 2 m sheet, with the cat in another room.
• Never leave an open bag on the floor; seal it in a lidded bin within 5 minutes.
• Water the plant in the sink, not over the carpet, and wipe the floor while damp.
• Keep the door closed for 48 hours, then vacuum with the cat out of the room.
• Watch at 30 minutes, 2 hours, 6 hours and 24 hours; call if any prill was eaten.

Frequently asked