Guides · Not enough light

Is my plant getting enough light?

Probably not, if it has grown long and thin since you bought it, the new leaves are smaller than the old ones, or it has stopped flowering. Too little light is the second most common reason a houseplant declines, and the slowest to show — a plant can sit in a dim corner for months looking fine while it quietly uses itself up.

By Sabz

What it is
A plant making less food than it spends, so it stretches towards the window, shrinks its new growth, and stops doing anything expensive: flowering, colouring, splitting its leaves
The tell
Long gaps between leaves, new leaves smaller and paler than the old, growth leaning to one side. Nothing wilts; nothing yellows at first
Urgency
Low. Weeks, not days. Move it this week and judge by the next leaf, not the ones it has
01

What is actually happening

A leaf is a solar panel. Light falling on it is turned into sugar, and the sugar is spent on everything the plant does: new leaves, roots, flowers, the coloured pigments in a croton or a calathea, the holes in a monstera. In enough light there is a surplus and the plant grows. In too little there is a deficit, and the plant does what a household does on a deficit: it stops spending.

The first things to go are the luxuries. Flowers stop. Variegation fades, because the white and pink parts of a leaf make no sugar and a plant in a deficit cannot afford them. A monstera's new leaves come in whole, because fenestrations are a response to light, not to age. Then the plant starts to stretch — longer stems, longer gaps between leaves, everything leaning towards the window — which is not growth so much as a search. The stretched growth is thin and weak, and it is the stretched stems that flop, snap and get pests.

What does not happen, at least at first, is anything dramatic. Nothing wilts. Nothing goes yellow and drops in a week. That is why light is misdiagnosed: the plant is watered, fed, repotted and moved, and the one thing it needed was to be a metre closer to a window.

02

What "bright indirect light" actually means

Every label says it and nobody measures it. Roughly: bright indirect light is the light within about a metre of a window that does not get direct sun for more than an hour or two — an east window, a north window in summer, a south or west window behind a sheer curtain or a metre back from the glass. It is bright enough to cast a soft shadow of your hand. Medium light is two or three metres from that window, or right beside a north one; your hand casts a faint shadow or none. Low light is anything further in, a hallway, a bathroom with a small window — and very few plants actually want it, they merely survive it.

The two things people underestimate: how fast light falls off with distance (a plant three metres from a window gets a small fraction of what it gets at one metre), and how much it drops in autumn. A south-facing room in June gets about sixteen hours of a high sun; in November it gets eight hours of a low one, often through cloud. The same plant on the same shelf is in a different climate. Most "my plant suddenly declined in October" stories are this.

03

The signs

No single sign is proof; the pattern is stretching and shrinking without wilting.

  • Leggy growth — long stems, long gaps between leaves, the whole plant leaning towards the window. The commonest and clearest sign.
  • New leaves smaller than old ones, often paler, sometimes a plainer green on a plant that should be marked or coloured. The plant is economising.
  • No flowers, or buds that form and drop. A peace lily, an African violet, an anthurium that has stopped flowering is nearly always short of light.
  • Monstera leaves without splits or holes; a swiss cheese vine with small solid leaves. Fenestration is a light response.
  • Variegation fading — a pink polka dot plant going green, a croton going dull, a marbled pothos coming in plain.
  • Lower leaves dropping slowly, one at a time, as the plant retreats to the growth nearest the light.
  • Soil staying wet for a long time. A plant in low light uses little water, so the routine that was right in a bright room is now overwatering — and that is the point at which light trouble turns into root trouble.

The check that settles it: look at the last three leaves the plant made. If each is smaller than the one before, it is running on a deficit.

04

What to do

Move it towards the window, not into the sun.
The fix for most plants is a metre or two closer to the glass, out of the direct beam. A plant that has adapted to shade will scorch if it goes straight onto a south sill in June; move it in stages over a fortnight, or put a sheer curtain between it and the sun.
Turn the pot a quarter every week.
Growth evens out and the lean stops.
Cut the leggy growth back.
It will not fill in on its own. Cut long bare stems back to two or three leaves from the base — pothos, philodendron, ivy, tradescantia, polka dot plant, pilea all regrow bushier from the cut, and the trimmings root in water.
Water less until it catches up.
A plant in a deficit drinks less. Water when the top few centimetres are dry, not on the day you used to.
Consider a lamp for the darkest spots.
A plain LED grow light on a timer, twelve hours a day, will keep a fern or a small tropical plant healthy in a room with no useful window at all. It is not cheating; in a British winter it is often the only honest answer.
Judge by the next leaf.
A leaf already made will not change. The signal that the move worked is the next one coming in larger, or with holes, or with colour — usually within four to eight weeks.
05

What not to do

  • Do not feed it. A plant short of light cannot use the food; the salts sit in the compost and scorch roots. Feed once it is growing again.
  • Do not repot it. Nothing is wrong with the roots, and a bigger pot of wet compost around a plant that is barely drinking is how light trouble becomes rot.
  • Do not move it straight into full sun. Scorch — pale, bleached patches on the leaves facing the window — is the mirror problem and it takes one afternoon.
  • Do not keep the old watering routine. This is the mistake that kills plants in low light: they do not die of darkness, they die of the water they no longer need.
06

Common questions

How do I know if my plant needs more light?

Look at the last three leaves it made. If each is smaller than the one before, or the stems between them are getting longer, it is short of light. Flowers stopping, colour fading and a monstera's leaves coming in without holes are the same signal. A plant short of light does not wilt or yellow at first, which is why it gets mistaken for something else.

What does bright indirect light mean?

The light within about a metre of a window that gets little or no direct sun — an east window, a north window in summer, or a south or west window behind a sheer curtain or a metre back from the glass. Bright enough to cast a soft shadow of your hand. Most houseplants sold in the UK want this, and most are kept in far less.

Can a plant recover from too little light?

Yes, but the leaves it has will not change — a leggy stem stays leggy and a solid monstera leaf stays solid. What recovers is the plant: moved closer to a window, the next leaves come in larger and better, usually within four to eight weeks. Cut leggy growth back to make it fill in.

Why is my plant leaning to one side?

It is growing towards the light, which means the light is coming from one direction and there is not enough of it. Turn the pot a quarter every week so it grows evenly, and move it closer to the window so it has less reason to reach.

Do grow lights work for houseplants?

Yes. A plain LED grow light on a timer, twelve hours a day, keeps ferns, calathea and most small tropical plants healthy in a room with no useful window, and gets a plant through a British winter that it would otherwise sulk through. It does not need to be expensive or purple; a full-spectrum white one is easiest to live with.

07

Plants this often affects

The ones that show it soonest are the ones grown for something expensive — monstera for its holes, croton and polka dot plant for their colour, peace lily and African violet for their flowers — and the ones that stretch, which is nearly every vine.

All 265 plants in the library →

08

Still not sure?

The RHS's guide to light for houseplants explains full sun, bright indirect and shade with examples; this page is the case where a plant is in the wrong one. Sabz's Check-up asks where the plant sits and whether it has been moved, and it weighs that against the season — because a plant that was fine in July and is stretching in October has usually not been moved at all; the light has. Pick Leggy or stretched growth or Small, pale new leaves, and it tells you whether the history points at light or at something else.

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