Room setups

Setting up a north-facing room: the 50 cm rule

A north window is not a dark window, it is a low-intensity window. The light at the glass is enough for a wide range of foliage plants; the problem is how fast it falls away with distance. Getting a north room right is mostly about respecting one number: 50 cm.

Room sheet · North-facing room
Orientation	NLow light
Glazing	One 1.2 x 1.4 m sash window, no overhang, no net curtain
Average light	300-800 lx at 30 cm, 80-200 lx at 2 m
Temperature range	16-21 C
Humidity band	35-50%
Species that work here	Golden pothos: the low-light plant that still needs some light, ZZ plant: the plant you are almost certainly overwatering, Snake plant: the plant that dies from kindness, Chinese evergreen: the dark-corner plant with a cold-water problem, Spider plant: brown tips, and why this one really is the water
What makes this room difficult	Light falls below 500 lx beyond 50 cm from the glass, which is the threshold below which most plants stop producing new leaves. Winter days are short and the light is weak, so growth effectively stops from November to February even for tolerant species. Rooms with the heating on sit at 35-45% humidity, which is low enough to crisp the edges of thin-leaved plants.

presentationWhat you are seeing

Plants placed on shelves two metres back from the window slowly stop growing, lose their lower leaves and become leggy, even though the room looks bright to human eyes.
Plants at the glass do well for a year and then decline as they outgrow the light available at that position.

aetiologyWhy it happens

Light intensity falls off roughly with the inverse square of the distance from the window aperture. A north window delivers 600-800 lx at 30 cm, around 300 lx at one metre, and 80-200 lx at two metres. Human eyes adapt to all three and read them as similar; plants do not.
Below roughly 500 lx a plant can maintain its existing tissue but has no surplus energy for new leaves. That is why a north-room plant often looks healthy and simply does not grow.
North light also has no direct sun, so there is no daily peak to compensate. The plant receives a low, flat level all day, which is adequate for shade-tolerant species and inadequate for anything else.

managementWhat to do

Put the plants that need light within 50 cm of the glass. That is the single change that makes the biggest difference, and it costs nothing.
Choose species matched to the conditions: pothos, ZZ plant, snake plant, Aglaonema and spider plant all manage at 400-800 lx. Do not attempt Aloe, Jade, Hoya or Strelitzia here.
Raise the plants to window height. A plant on the floor beneath a windowsill receives a fraction of the light available at the glass, because the sill shadows it.
Wash the glass inside and out twice a year. Dirty glass can cut transmission by 20-30%, which matters far more in a low-light room than in a bright one.
Consider a small grow light for the winter months. Twelve hours a day at 20-30 cm from a 10 W LED will lift a north-room shelf from 200 lx to 5,000-8,000 lx and transform the growing season.
Reduce watering in winter. A north-room plant in November uses a fraction of the water it used in June, and watering to the summer schedule is the fastest way to rot its roots.

What grows well here, and what does not

The species that thrive in a north room are the understorey plants: those that evolved on a forest floor receiving a few hundred lux for most of the day. Pothos, ZZ plant, snake plant, Aglaonema, spider plant, Monstera (slowly), and most ferns manage comfortably.

The species that do not are the ones that evolved in full sun or in the canopy: Aloe, Echeveria, Jade plant, Hoya, Strelitzia, bird of paradise, and most herbs. Putting these in a north room produces a plant that survives for a year and then fails, having spent its reserves on stretched growth.

The useful test is what the plant looks like after six months. Compact, dark green and producing new leaves at the rate it did when you bought it means the position works. Pale, stretched, with wide gaps between leaves, means it does not.

Thrives at 400-800 lx: pothos, ZZ plant, snake plant, Aglaonema, spider plant, ferns
Survives with slower growth: Monstera, Philodendron, Dracaena
Will not work: Aloe, Echeveria, Jade, Hoya, Strelitzia, herbs
Within 50 cm of glass: the useful zone
1-2 m back: maintenance only, no new growth

The winter problem, and the grow light calculation

In a north room in December at 51 degrees north, the light at the glass at midday may be 400-600 lx, and it may be that level for only five hours. That is a quarter of the summer figure. Even a shade-tolerant plant goes into maintenance mode.

This is where a grow light is genuinely worth it. A 10 W LED panel at 25 cm delivers roughly 8,000-12,000 lx directly beneath it, and at 40 cm about 3,000-5,000 lx. Even the 40 cm figure is five to ten times what the north window is delivering in December.

Run it for twelve hours a day on a timer, positioned so the light falls on the plant rather than on the room. A shelf with a strip light above it is the most efficient arrangement: it lights the plants and nothing else.

Watering in a low-light room

Water use is driven by light. A plant at 600 lx transpires a small fraction of what the same plant transpires at 6,000 lx, so its water consumption falls by a similar factor. This is the most common way that a north-facing room kills plants: not lack of light, but watering at the summer rate in a room where the plant has stopped drinking.

The practical approach in a low-light room is to check the mix at 5-6 cm rather than 3-4 cm, and to expect to water roughly half as often as you would in a bright room. In a cool north room in winter, a 20 cm pot of Aglaonema may need water every three to four weeks.

The early symptom of overwatering in a low-light room is yellow lower leaves. The plant cannot use the light, cannot use the water, and starts sacrificing leaves to reduce demand.

Troubleshooting

Can I grow anything flowering in a north-facing room?

Spathiphyllum (peace lily) and Aglaonema will both flower intermittently at 400-800 lx, and both are genuinely shade-tolerant. African violet will flower at 1,000-2,500 lx, which a north window can reach at the glass. Almost everything else needs more light. A small grow light expands the list to almost anything.

Is a mirror on the wall behind the plant useful?

Marginally, and less than people hope. A mirror reflects light back but it does not increase the total, and the reflected beam comes from a different angle rather than adding to what the leaf is already receiving. A white wall behind the plant is more useful than a mirror, because it scatters light evenly rather than sending a single beam back.

My north-room plant looks fine but has not grown in eight months. What should I do?

Measure the light at the plant's position at midday. If it is under 500 lx, the plant is in maintenance mode and that is the whole explanation. Move it within 50 cm of the glass or add a grow light. You should see new growth within six weeks of the change.

CaveatLight and humidity figures are measured ranges from one specific position, not guarantees. A room's readings shift with season, glazing, nearby buildings and whether lights are on in the evening, so measure your own spot before buying a plant for it.

Published2026-09-07 · By The Foliage Desk