How much light does my plant get? A window light check
How much light a plant gets depends mostly on three things: the way the window faces, how far the plant sits from it, and whether anything outside or on the glass shades it. Pick yours below and the check names the light band, which is the same word plant labels use: direct sun, bright, medium or low light.
The answer for every window
Without the form, find your window in the table. These are for an unshaded window in the northern hemisphere (the US, Canada, Europe, most of Asia), after the University of Illinois Extension's lighting table. The columns are the distance from the glass: on the sill, about 1 m (3 feet), 1 to 3 m (3 to 10 feet), and over 3 m.
| Window | Sill | 1 m | 1 to 3 m | Over 3 m |
|---|---|---|---|---|
| North | Medium | Low | Low | Low |
| East | Bright | Medium | Low | Low |
| South | Direct | Bright | Medium | Low |
| West | Bright | Medium | Low | Low |
If a tree, building, balcony, awning or sheer curtain shades the window, read one step lower: direct sun becomes bright light, bright becomes medium, and medium becomes low.
In the southern hemisphere (Australia, New Zealand, South America, southern Africa), swap north and south: a north window gets the most sun and a south window the least. Near the equator the sun crosses from one side of the sky to the other over the year, so there east and west windows are the steadier guide.
| Window | Sill | 1 m | 1 to 3 m | Over 3 m |
|---|---|---|---|---|
| North | Direct | Bright | Medium | Low |
| East | Bright | Medium | Low | Low |
| South | Medium | Low | Low | Low |
| West | Bright | Medium | Low | Low |
What each light band means
- Direct sun. The sun shines on the leaves for part of the day. This suits plants whose label says full sun or direct light. Leaves of plants sold for indirect light can scorch here; a sheer curtain or a step back from the glass softens it.
- Bright light. Close to the window with little direct sun on the leaves. This suits plants whose label says bright, indirect light, which is what many common houseplants are sold for.
- Medium light. Daylight, but no sun on the leaves. This suits plants whose label says medium or partial light. Plants sold for bright light often grow slowly here and lean toward the window.
- Low light. Far from the light, or beside a dim window. Plants sold as low-light tolerant can live here but grow slowly; most others grow long and thin toward the window.
A west window gets afternoon sun, which is warmer than the morning sun of an east window. In winter the days are shorter, so a spot usually gets less light than in summer; a tree that is bare in winter shades the window in summer.
Check it with your hand
At midday, hold your hand about a foot (30 cm) above the spot. A sharp, dark shadow means direct sun; a soft-edged shadow means bright light; a faint, blurry shadow means medium light; and barely any shadow means low light. It is a rough check: a light meter, or a light meter app, gives a number in lux or foot-candles.
Signs the light is wrong
- Too little: long, thin stems with wide gaps between leaves, small new leaves, and the plant leaning hard toward the window. The leggy plant guide covers what to do.
- Too much: pale, bleached or crisp brown patches on the side facing the glass, often after a plant was moved to a sunnier spot.
If you move a plant into brighter light, move it in steps over a week or two rather than all at once, and turn the pot now and then so it grows evenly.
Questions
Which window is best for houseplants?
The one that matches the plant: read the light on its label and find a spot in that band. In the northern hemisphere a south window gives the most light, east and west windows are in the middle, and a north window gives the least; in the southern hemisphere north and south swap.
How far from a window is bright, indirect light?
Next to an unshaded east or west window, or a few feet back from a south window in the northern hemisphere (a north window in the southern hemisphere). Light drops quickly with distance: a few steps back into the room can be a whole band darker.
Is a north-facing window enough for plants?
In the northern hemisphere, a north window gives medium light right at the glass and low light a few feet back. That suits plants sold for low or medium light; plants that need bright light usually grow slowly and stretch there.
Does a sheer curtain block too much light?
A sheer curtain takes direct sun down about one band, to bright light, which is often what plants sold for indirect light want. A heavy curtain or blind, closed for most of the day, leaves little light at all.
Sources
- University of Illinois Extension, Lighting (houseplants): window direction by distance.
- UF/IFAS Gardening Solutions, Light for houseplants: the light levels, and how shade lowers them.
- Oregon State University Extension, Light exposure key for growing successful houseplants: which windows give the most and least light.
The hand check, the signs of too much light, the warmer west sun and moving a plant in steps are common care advice rather than from these pages.
If a plant already looks wrong in its spot, Leafsight assesses it from a photo: the likely problem, how sure it is, and what to try first.