How to judge the light in your home

Why light matters so much

A plant makes its food from light. In a home, lack of light is the factor that most often limits growth: a poorly lit plant slowly weakens, however good the rest of its care.

Three aspects are involved: intensity (how much light the plant receives), duration (how many hours of light per day), and quality (the makeup of the light). When placing a plant, intensity matters most. Even plants known for tolerating shade grow better and look their best in bright indirect light: “tolerates” doesn’t mean “prefers.”

The categories used in our profiles

Outdoors, exposure is described in hours of direct sun: full sun (six hours or more a day), partial shade (two to six hours), shade (less than two hours), or dappled light through foliage. Verdepedia’s profiles translate these into four indoor benchmarks:

Category	What it looks like indoors
Direct sun	Several hours of sun on the plant, right by a well-exposed window
Bright indirect light	A very bright room, near a window; the sun doesn’t reach the leaves, or only early in the morning, or through a sheer curtain
Medium light	Some distance from a window, no direct sun
Low light	Far from windows, a hallway, a window that never gets direct sun

“Bright indirect light,” the most frequently recommended, is light strong enough to cast a distinct shadow, without the sun’s rays striking the foliage directly.

Window orientation

The direction a window faces determines how much sun it lets in. It depends on your hemisphere: the brightest window is the one facing the equator, meaning south in the Northern Hemisphere and north in the Southern Hemisphere.

Equator-facing window: the most abundant light, with direct sun for much of the day. Ideal for sun-loving plants, it can scorch others from late spring to early fall.
East-facing window: abundant light and gentle morning sun, which suits many plants.
West-facing window: abundant light, but afternoon sun is more intense and can be too strong for some species, such as the ZZ plant.
Pole-facing window: no direct sun; it suits low-light plants.

Distance: the underrated factor

Light drops off very quickly as you move away from the glass. As a rule of thumb, a plant 5 ft from an equator-facing window gets about as much light as one on the sill of an east- or west-facing window. Beyond 8 ft from any window, you are already in low light. Often, a spot more than a few steps from even a bright window doesn’t get enough light for most plants to truly grow.

The Chinese banyan (Ficus microcarpa), for instance, should stay within about 3.5 ft of the brightest window. A plant “near the window” at 6.5 ft receives only a small fraction of the light available on the sill.

What blocks the light

Many things reduce the light coming through a window: curtains and sheers, roof overhangs, a balcony above, but also trees, hedges, neighboring buildings, walls, or fences. The closer an outdoor obstruction is to the window, the greater the loss. A well-oriented window facing a narrow courtyard can therefore let in less light than a less favorable but unobstructed one.

Measuring the light in a spot

The shadow test: around midday, hold your hand about 12 in above the intended spot. A sharp, well-defined shadow means bright light; a fuzzy shadow, medium light; a barely visible shadow, low light.
A light meter or smartphone app: gives a numerical reading of intensity, useful for comparing several spots.
The plant itself: its shape and color after a few weeks are the best indicator (see below).

Repeat the assessment through the year: the same spot changes a great deal from one season to the next.

Seasons change everything

In winter, days are shorter and the sun sits lower: light intensity and duration drop noticeably. A plant that was well placed in summer may now fall short. Move it closer to the brightest window during the cold season; a monstera, for example, then benefits from a little direct sun.

Conversely, from late spring to early fall, sun coming through an equator-facing window can scorch plants that don’t need bright light. Move them back a little from the glass or filter the light with a sheer curtain.

Signs that the light doesn’t suit

Sign	Likely cause
Long, spindly stems stretching toward the window	Too little light
Smaller, paler, or yellowing leaves, little or no growth	Too little light
Few or no flowers	Too little light
Fading variegation, leaves turning plain green (pothos)	Too little light
New leaves without splits (monstera), leaf drop (Chinese banyan)	Too little light
Leaves that pale, then turn brown and die	Too much light
Dry brown or bleached patches, scorched edges	Sunburn

The plant’s shape tells you something too: in the snake plant, leaves stretch out in shade and stay more compact in sun. Keep in mind, though, that yellowing or leaf drop can also come from watering, cold, or root problems. Cross-check the clues, as explained in Water by observation, not by the calendar.

Moving and upkeep

Change exposure gradually: a plant used to a dark corner and suddenly placed in full sun can burn. Move it toward the light in stages.
Turn the pot regularly: plants lean toward the light. A quarter turn now and then keeps growth balanced.
Dust the leaves: dust blocks light. Wipe smooth leaves, top and underside, with a soft damp cloth; use a soft brush on hairy leaves.

Supplemental lighting

When no window is enough, a grow light can take over. LED models are now the standard: energy-efficient, long-lasting, and cool-running. Place them about 12 in above the foliage and run them twelve to sixteen hours a day, but not around the clock: most plants need a dark period each night.

Choosing the plant for the spot

It’s better to fit the plant to the place than the other way around. For a dim corner, the cast iron plant, the ZZ plant, and the snake plant are among the most tolerant, even if they grow slowly there. For a bright room without direct sun, monstera and golden pothos do well. For a very bright window with some sun, the Chinese banyan.

Two kinds of plants need more light. Variegated forms have less chlorophyll: in shade their colors fade, and the paler a cultivar, the more light it needs… and the more easily it burns in direct sun. Plants grown for their flowers also need more light: in low light they bloom little or not at all, even if the foliage looks fine.

At a glance

Question	What to check
Which orientation?	Equator-facing, east, west, or pole-facing window
How far?	Light drops sharply beyond the area close to the glass
What obstacles?	Sheers, balconies, trees, buildings
What season?	Move closer in winter, shield from strong sun in summer
What does the plant say?	Stretched stems = too little; scorched patches = too much sun

To sum up: note the orientation, measure the distance to the glass, do the shadow test, then choose a suitable plant. Watch it for a few weeks afterward: the plant will confirm, or not, your assessment.