Peace Lily

The office plant with the white sail - and the most misidentified plant in any conversation about cats. A peace lily is not a lily at all. It burns a chewed mouth, and that is where it ends; the plant that kills cats is Lilium, and it is a different thing entirely.

Low to moderate indirect light, ordinary potting mix kept evenly moist, and no direct sun. The two things it is fussy about are tap water and fertilizer, both of which show up as brown tips.

Light. Low to moderate indirect light. A north-facing window, a few feet back from an east-facing one, or an interior office under fluorescent tubes all work — this plant genuinely earned its nickname of closet plant. What it will not take is direct sun, which scorches pale dead patches into the leaves within a couple of days. There is a trade-off worth knowing: it survives in deep shade but only flowers in moderate light, so if the white sails matter to you, brighter is better.

Mix and pot. Nothing special — ordinary peat or coir potting mix in a pot with drainage holes. Peace lilies actually flower better slightly pot-bound, so resist repotting until roots are circling the pot or pushing out of the base, and then go up only one size, in spring.

Water. Evenly moist, never soggy, never bone dry. Water thoroughly when the top inch is dry and empty the saucer afterwards. This is the one houseplant that will tell you out loud: it collapses when thirsty and recovers within hours. Use that as a backstop, not a routine — every hard wilt costs fine roots, and the bill arrives later as brown leaf tips.

The brown-tip problem. Almost every peace lily eventually gets crisp brown leaf tips, and the causes are nearly always fluoride and chlorine in tap water, fertilizer salts in the pot, or repeated hard wilting — in roughly that order. Spathiphyllum is unusually sensitive to fluoride. Let tap water stand overnight, or use rainwater, filtered or distilled water; feed at quarter to half strength and no more than every six weeks in the growing season; and flush the pot through with plenty of plain water two or three times a year to wash salts out.

Warmth and air. Above 55°F, out of drafts, away from radiators and heating vents. It likes humidity and shows dry air as brown edges, so a bathroom, a pebble tray or a group of plants together all help.

Cut spent spathes and tired leaves right down at the base, wipe the leaves, divide it when it fills the pot, and expect it to flower less at home than it did in the shop.

Deadheading. A white spathe lasts several weeks, then turns green, then brown. Nothing has gone wrong; that is a flower finishing. Follow the stalk all the way down to the base of the plant and cut it off there rather than trimming the brown top, which leaves an ugly stub. Yellowed outer leaves come off the same way. Wear gloves — the cut stems weep sap that stings skin and is properly painful in an eye.

Leaf care. Wipe the leaves with a damp cloth every month or two. Those broad glossy surfaces collect dust that dulls them and cuts the light the plant can use, and a clean peace lily looks twice the plant. Leaf-shine products are unnecessary and clog the pores.

Repotting and division. It flowers better slightly crowded, so repot only every two or three years, one size up, in spring. When a plant has filled its pot with several crowns, the better move is to divide it — see Propagation.

Why it flowered so well in the shop and not since. This one catches everybody. Commercial growers treat peace lilies with gibberellic acid, a plant hormone that forces a heavy, uniform flush of spathes for the sales floor. A plant bought in full bloom is a plant that has been pushed, and at home it reverts to its natural rhythm: a few flowers in spring and summer, given decent light, and possibly none at all in a dim corner. Nothing is wrong with your plant. It was never going to keep that up.

If a pet or child chewed a leaf, call the vet or poison control now - and read the reassurance about true lilies while you do. Beyond that: brown tips are water quality, yellow leaves are too much water, and no flowers is too little light.

My cat chewed a peace lily and I have read that lilies kill cats. Call your veterinarian or an animal poison line now and describe what happened — that advice does not change. But take this with you to the phone: a peace lily is not a Lilium. It does not cause the acute kidney failure that true lilies cause. What you should expect is drooling, pawing at the mouth, maybe some vomiting and a swollen lip, and recovery within hours. Rinse the mouth if the animal will let you, offer water, and watch. Go to an emergency clinic at once if drooling will not stop, if swallowing is difficult, or if breathing or the voice changes. The same applies to a child, with a call to poison control.

Brown crispy leaf tips. The classic peace lily complaint. In order of likelihood: fluoride and chlorine in tap water, fertilizer salts built up in the pot, letting it wilt hard repeatedly, and dry heated air. Switch to stood-out, filtered or rainwater, flush the pot through with plenty of plain water, halve the feed, and water a little sooner. Existing brown tips will not turn green again — trim them to shape with scissors and judge success on the new leaves.

The whole plant has collapsed. Feel the mix first. Dry means thirsty: water thoroughly and it will be standing up in a few hours. Wet means root rot, and watering again will finish it — unpot it, cut away the soft brown roots and repot the sound remainder in fresh mix.

Yellow leaves. A single yellow outer leaf on a healthy plant is just an old leaf being retired; cut it at the base. Several at once, with damp mix, is overwatering.

It will not flower. Almost always too little light. Move it somewhere brighter but still out of direct sun and give it a season. Also see the note in Care about shop plants forced with gibberellic acid — the display it arrived with was not natural.

The flowers are coming out green. Usually too much fertilizer, sometimes too much light, and sometimes just a spathe ageing on schedule. Ease off the feed.

Black leaf edges and streaks. Overwatering or cold. Check the saucer and check what the plant is leaning against in winter.

Division is the only method that works - a peace lily will not grow from a leaf or a stem cutting, no matter how long you leave it in water.

Peace lilies are propagated by division, and only by division. This is worth saying plainly, because so many houseplants root from a cutting that people try it here and leave a leaf in a jar for months waiting for something to happen. It never will: a peace lily leaf has no node and no growing point, so it cannot become a plant.

What it does instead is make new crowns from the base, so a mature plant is really a colony of small plants sharing a pot. To divide it, choose a moment in spring or early summer, water the plant the day before, and turn it out of its pot. Tease the root ball apart with your fingers and look for natural separations — each division needs at least two or three leaves and its own visible roots. Pull them apart by hand where you can and cut with a clean knife where you cannot.

Pot each division into a container only slightly bigger than its roots, in ordinary potting mix, water it in, and keep it somewhere warm, shaded and out of drafts. Expect it to sulk for two or three weeks, and do not feed it until you see new growth. Small divisions establish faster than heroic ones.

Wear gloves for the whole job, keep the trimmings off kitchen counters and away from pets, and wash your hands afterwards.

An indoor plant across the whole US. Outdoors it needs zone 10b or warmer, deep shade and constant moisture - and unlike pothos and monstera it is not a known escape risk.

Indoors, anywhere. A peace lily wants what a heated house already provides: 65 to 80°F, out of drafts, away from cold glass in January and away from radiators and heating vents, which dry the air and brown the leaf edges. It sulks below about 55°F and is killed outright by frost. Of all the common houseplants it is the most tolerant of genuinely dim rooms, which is why it colonised offices in the first place.

Outdoors, only zone 10b and warmer — south Florida, Hawaii, coastal Puerto Rico, the frost-free Gulf. There it works as a shade groundcover under trees or on a north wall, in soil kept steadily moist. It burns badly in any sun and stops dead in dry soil, so it is a plant for genuinely shaded, irrigated positions rather than open beds.

One honest contrast with its relatives: peace lily is not a recognised invasive problem in the continental United States. Pothos and monstera both climb and smother trees where they escape in Florida and Hawaii, and this entry does not ask you to treat Spathiphyllum the same way. It is a slow clumping plant that spreads only as far as its own crowns reach. Ordinary care with prunings and old potting mix is enough.

Summering outdoors anywhere else is fine and does it good: deep shade only, once nights stay above 60°F, and back inside in early autumn well before the first cold night — checking the leaf undersides for hitchhiking pests before it rejoins the other plants.

A rainforest floor plant that became the emblem of the corporate lobby, picked up a lily's name it never deserved, and got famous on the back of an air-cleaning study that does not scale to a real room.

Spathiphyllum is a genus of around forty species from the rainforest floors of tropical America, with a handful more from Southeast Asia and the western Pacific. They are understorey plants: broad thin leaves for catching what light gets through, and constant moisture underfoot. Almost everything sold today is a hybrid, and the big classic cultivar — 'Mauna Loa' — has been in the trade since the middle of the twentieth century.

The name is the problem. The white spathe reads as a lily to a nurseryman naming a product, and peace lily stuck, alongside white sails and closet plant. It is one of a long list of unrelated plants sold as lilies — daylily, calla lily, rain lily, lily of the valley — and that list is a genuine hazard rather than a curiosity, because two of those (daylily and true Lilium) are lethal to cats while the rest are not. When toxicity is the question, go by the botanical name.

The plant's commercial rise came with the open-plan office. It tolerated fluorescent light, dry air and inattentive watering, it flowered on demand under grower hormone treatment, and it looked like something. By the 1980s it was in every lobby in America.

Its other fame is worth an honest correction. The 1989 NASA Clean Air Study tested peace lily among other houseplants and found it removed formaldehyde, benzene and other volatile compounds from the air — inside a sealed chamber the size of a fish tank. A 2019 review reworked those numbers against the rate at which a real room already exchanges its air and found you would need something on the order of a hundred plants per square metre of floor to match simply opening a window. Grow a peace lily because it is handsome and forgiving. It is not an air filter.