Peace Lily Problems: Yellow Leaves, Brown Tips, Pests and Root Rot

Check the compost before anything else

The same symptom on a peace lily means opposite things depending on whether the pot is wet or dry. Diagnosing without touching the compost is how people end up watering a plant that is already drowning, which is the most common way a peace lily dies.

A sour, stagnant smell from the compost is decisive. Healthy compost smells of earth; rotting roots smell sharp and unpleasant, and no amount of adjusting the watering will fix that on its own.

Root rot is the main killer

Root rot follows compost that stays saturated, usually from watering to a routine, leaving the saucer full, using a pot with poor drainage or over-potting. In a cold room it develops far faster, because the plant is using almost no water at all.

The tell is a plant that droops while the compost is clearly damp. Healthy roots are white to cream and firm; rotted roots are brown or black, soft, and the outer sheath slides off between your fingers leaving a thread behind.

1. Take it out and look Slide the plant from the pot and examine the rootball. This tells you more in thirty seconds than a week of watching the leaves.
2. Cut out everything rotten Trim away all soft brown roots with clean scissors until only firm pale root remains. Wash the remaining roots gently to remove the old sodden compost.
3. Reduce the top to match Remove enough of the oldest outer leaves that the remaining foliage is in proportion to the roots you have left. A full crown of leaves on a third of a root system will not survive.
4. Repot small and free draining Use the smallest pot that fits the remaining roots, with fresh open potting mix. A big pot at this stage guarantees the rot returns.
5. Then leave it nearly dry Water once to settle it, then keep the compost barely damp and the plant somewhere warm and shaded. Do not feed for at least a month.

Recovery takes months and you may lose most of the leaves. If several crowns survive, the plant usually comes back. If the crown itself has gone soft and brown, it will not.

Yellow leaves, one at a time or in numbers

One or two of the oldest, outermost leaves turning yellow and dying back is ordinary turnover, especially in autumn and winter. A peace lily sheds old leaves as it makes new ones, and it is not a problem to solve.

Several leaves yellowing at once, or younger inner leaves yellowing, is a signal. Wet compost points to overwatering and the start of rot; bone dry compost and a history of collapses points to root damage from drought; uniform pale yellowing across the whole plant in a growing plant usually means it has not been fed for a very long time.

1. Remove yellow leaves at the base Cut the stalk right down at the crown with clean scissors. A yellow leaf will not turn green again and the plant is still spending resources on it.
2. Do not feed a sick plant Fertilizer on damaged roots makes things worse. Fix the watering, get new growth started, and only then resume feeding.
3. Look at what changed Yellowing that starts two or three weeks after a move, a repot or the heating going on is almost always about that change rather than about anything new.

The pests you will actually see

Peace lilies get few pests compared with most houseplants, and the handful they do get are all favored by dry, warm, still indoor air. Check the leaf undersides and the crevices where leaf stalks meet the crown, which is where every one of them starts.

The large flat leaves make physical removal unusually effective, so most infestations caught early can be dealt with by washing rather than by any product at all. Isolate an affected plant from your others straight away: spider mites in particular spread across a windowsill within days, and they are far harder to clear from five plants than one.

1. Wash it in the shower Support the compost with your hand and rinse the whole plant, especially the leaf undersides, with tepid water. This alone knocks mites and aphids right back.
2. Wipe both leaf surfaces Support each leaf and wipe it with a damp cloth. Doing this monthly as routine prevents most infestations from ever establishing.
3. Treat repeatedly, not once Eggs survive a single treatment. Whatever you use, repeat it every five to seven days for three rounds or the population simply rebuilds.
4. Raise the humidity Spider mites need dry air. Grouping plants, using a pebble tray and misting the undersides makes the plant a much less attractive host.
5. Deal with gnats at the surface Fungus gnat larvae live in the top inch of wet compost. Letting that inch dry between waterings breaks the cycle.

Damage that is not a pest or a disease

A good proportion of peace lily problems come from the environment rather than anything living, and they are easy to tell apart once you know what each looks like.

Write down the date you first noticed a problem, what the compost was like at that moment, and what you changed. Pest outbreaks and rot both recur at similar times of year, and a one-line note from last winter will save you the whole diagnosis this winter. Note treatment dates too: the commonest reason a pest treatment fails is that the second and third rounds never happened.

None of this damage heals. Judge whether a treatment worked by whether the new leaves come out clean, not by whether the damaged ones improve.

Toxicity and handling

Every part of a peace lily contains calcium oxalate crystals. Chewed by a pet or a child they cause immediate burning of the mouth, drooling and swelling. It is rarely dangerous because the pain stops most animals after a single bite, but it is genuinely unpleasant and worth taking seriously.

Keep the plant out of reach of cats, dogs and small children, and clear up any fallen leaves. Wear gloves when dividing or cutting, and wash your hands afterwards, because the sap also irritates skin and does real damage if you then rub your eyes.