Plants without a window

There are two honest ways to keep a plant in a room with no window. Put a grow light on a timer above it, or run two sets of plants and swap them with a bright room every few weeks. Everything else is a countdown.

Your eyes adjust to a lit office and read it as bright. Plants do not work on that scale. Daylight outdoors, daylight next to a window and office ceiling light are separated by far more than they look, and the gap is what the plant lives on.

Standard fluorescent panels and downlights are built for reading, not for growing. They put out little of the intensity a leaf needs, and they usually run only during working hours.

A plant in that room lives off its reserves. Thick leaved species carry more reserve than thin leaved ones, which is why a ZZ plant holds up for months and a fern is finished in weeks.

The first signs are quiet. New leaves come in smaller and paler than the ones before them, the stem stretches between leaves, and the plant stops drinking, so the mix stays damp for a very long time.

This is the fix that lets a plant actually live in the room. A grow lamp above the pot, running on a plug in timer for a block of hours each day, replaces the window.

Height and running time depend on the lamp and the species, and the maker’s instructions are the place to get them. As a rule the lamp needs to be close enough that the light does not spread out into the room and to run well past the length of a meeting.

Give the plant a dark period every day. Light around the clock does not make it grow faster and it stops the plant from resting.

The lamp is also office equipment plugged in overnight, so check with whoever manages the space before you install one. A small clip lamp is usually easier to get agreed than a fixture.

The other honest approach is to treat the windowless room as a display spot rather than a growing spot. The plant lives near a window somewhere in the building and takes a turn in the dark room.

Two identical plants make this easy. One sits in the office, one recovers in the bright room, and they change places every couple of weeks. Put a note in a calendar, because the swap gets forgotten and that is what kills the plant.

The plant in the bright room is the one that needs watching. It grows, dries out faster and needs the water. The one in the dark room needs very little.

Any of the tolerant species below survive this pattern. Thin leaved plants such as ferns and calatheas do not, because they react to the change within days.

ZZ plant is the most durable choice. Thick rhizomes and firm leaves mean it can coast on stored water and stored energy longer than anything else on the shelf, and it takes weeks without water.

Cast-iron plant earns its name in exactly this situation. It grows in dark hallways and cool corners where nothing else does, and it asks for almost nothing.

Snake plant holds its upright shape well in low light and needs very little water there. Wet mix is the only thing that reliably kills it.

Golden pothos keeps growing in dim light, though the new leaves come in smaller and the variegation fades toward plain green. It is the easiest one to swap in and out of a bright room.

Chinese evergreen tolerates a dim spot and comes in dark leaved forms that hold up better than the pale patterned ones.

Parlor palm handles a shaded corner and gives an office some height. It wants steady water and no draft.

Peace lily copes with low light but shows a shortage of water within hours, so it needs somebody who checks it. In a windowless room it stops flowering.

Leave ferns, calatheas, fiddle-leaf figs and succulents out of a windowless room entirely. All of them want more light than the room can give and decline visibly.

Whether any of these matters around pets is covered in the plant’s own care guide.

Water much less than you would at a window. A plant that is barely growing barely drinks, and the mix in a dim room stays damp for weeks. Most plants that die in a windowless office die of wet mix rather than of darkness.

Feel the mix an inch or two down before every watering and skip it if there is any dampness. Empty the cachepot after half an hour, because nobody looks inside one in an office.

Skip fertilizer. Feeding a plant that is not growing leaves salts in the pot and does nothing for the leaves.

Wipe the leaves every few weeks. Dust cuts the little light the plant gets, and the wipe is when you spot pests early.

Turn the pot a quarter turn each time you water so the same side does not always face what light there is.

Some rooms are not worth the effort. A windowless meeting room used twice a week does not justify a lamp on a timer and a person responsible for a plant.

In that case use cut stems in water and change them out, or accept an artificial plant and dust it. Neither is a compromise on care, because a plant that dies slowly in a corner looks worse than either.

If the room has a glass wall onto a bright corridor or an atrium, measure that before giving up. Borrowed daylight through glass is real light and can be enough for the toughest species.

The other option is to move the plants to where the daylight already is. A row of pots along a bright corridor gets seen by more people than one struggling plant in a windowless room.