“Low Light” Corners: What Lux You’re Actually Getting 6–12 ft From a Window (and Which Plants Tolerate It)

“Low light” is often dimmer than plant tags suggest—especially 6–12 ft from a window. Learn how to estimate and measure lux in your corner, convert foot-candles to lux, and choose houseplants that can tolerate true low,

When you place a “low-light” houseplant in an indoor corner and see it slowly declining over time, you may very well be correct to think it is in decline. This is due to the fact that most corners with plants 6-12’ away from windows are significantly darker than your eye may perceive and, very often, these corners are also much darker than what many low-light plant-care guides suggest. This article discusses how to determine how dark your space is by measuring the light-lux levels so that you may select plants to grow that have the ability to tolerate the amount of light/lux in that particular space.

Quick Notes

• Our eyes will adapt so if you think your plant is receiving enough light because it “looks bright,” it is not the best way to evaluate light for plants, it’s best to measure the amount of light/lux.
• As a rough estimate of how much light drops off as you move from the window, it can drop significantly (i.e. – by quite a lot) within a distance of between 6-12’ of the window.
• Low-light houseplant references show low light to represent around 25-100 ft-candles (which is equivalent to around 270-1,080 lux). In actuality, many homes can see their corner locations receive less than those amounts of lux.
• Some good low-light plants that are also realistic in terms of being true to their name include Snake Plant, ZZ Plant, Cast Iron Plant, Pothos (the greener variety), Heartleaf Philodendron, Chinese Evergreen, and Peace Lily (this plant will live but may not flower).
• If your corners see lux-levels consistently that are around the 100-200 lux or below, the addition of a small grow-light will significantly improve the difference from just surviving to actually growing properly.

What Are Lux (lx), Foot-Candles (fc), And Why the Confusion About Low-Light Houseplants

The terms “bright indirect light” (or “low light”) used on some plant labels are not a true measure because they are user-defined descriptive terms. In many cases, Extension Resources indicate that our eyes are very adaptive and therefore, what may appear (to the naked eye) as similar emotional levels of brightness, may not have the same quantitative amount of light/lux. Therefore, using lux (lx) is a practical and real-world way of measuring a realistic determination of what light your plant is receiving. When growing indoor plants, you’ll mostly deal with two different types of measuring units—lux (lx) and foot-candles (ftc). Extension charts on houseplants in North America use the measured unit of foot-candles while most free app-based tools and inexpensive measuring devices display the unit measurement in lux.

The chart below is an approximate conversion between foot-candles and lux, based on the average of measurements taken for deciding best houseplants for light requirements.

Lighting drops off quickly as you move away from the window (approx. six to twelve feet)

Indoors, light coming from a window drops off quickly as you move away from the glass window (source). The first reason for this corresponds closely with basic physics; illuminance decreases (as noted above) based on the distance to (roughly) an infinitely small point source (within the distance that light travels). Window reflections can cause quite a large change in light levels, but real-world windows are not true point sources; the “drops fast with distance” concept still applies as a general guideline.

• Distance – Moving from 2 feet to 8 feet creates quite a difference.
• Angle or Direction – If you are in a location that has little sky visible from the window, it will be dimmer than if you are in a location that has much sky visible.
• Orientation of the Window – The effect on peak daylight and on receiving direct sunlight from a window located North (U.S.) compared to a South facing window.
• Obstructions – Trees, other buildings, porches, deep window wells.
• Window material and treatments – Insect screens, tinted glass, shades and sheer curtains all reduce the amount of light coming into a room through windows.
• Reflectivity of the Room – White walls and ceilings reflect (bounce) more light as opposed to dark walls and large dark furniture, which absorb more light.

A good way to measure your lux at 6-12 feet from windows (using your baseline lux from a window)

Instead of estimating lux at your corner; measure near the window (approximately at the height of your plant’s leaves); then use that lux to estimate what the lux level would be 6-12 feet away to use as a starting point for your final measurement at the corner (next section).

1. Measure your lux approximately 1 foot away from the window (not in the middle of a direct sunlight beam unless that is where your plant will be).
2. Record that lux number down (if possible, try to measure midway as well as in the morning and afternoon).
3. Use the following formula to make a rough estimation: lux_at_distance ≈ lux_near_window divided by (distance in feet squared).
4. Use your result as a “ballpark” figure. Actual levels will be higher (large windows, white walls) or lower (shades, insect screens, porch overhangs, dark colours).
5. Finally use real measurements and not estimates to accurately find lux measurements after 6-12 feet from windows at points throughout the room (next section). Next, take a Lux measurement where you want to put your plant. This is your “expectation setter only,” not a method to find out what kind of light is available.

Example: If you take a reading close to the window …your estimates of the total light from where you plan to place the plant (in a straight line to the window) would be approximately: 6ft -> 1,000/36 = ~28, 12ft -> 1,000/144 = ~7. Here are some examples of what those plants might look like at 6ft and 12ft respectively:

Measuring lux in your corner (so you don’t have guess anymore)

The fastest way to end the “low-light” guessing game is to measure. A digital light meter will provide a dedicated device, but under certain circumstances, a phone app can provide enough accuracy to obtain accurate measurements, if you are consistent with its use and if you focus your comparisons to areas of your home.

1. Choose the exact location of the plant. Measuring lux at leaf height is the most accurate, so do not measure from your eye level.
2. Hold the sensor (or phone) flat, facing up, in a position, corresponding to the leaves. Take an average of 2–3 readings and calculate that number.
3. Make sure you measure at the same time every day (for example: late morning and mid-afternoon). If you only measured once, do it at midday.
4. If possible, repeat the measurement on the next day (a sunny day, compared to an overcast day, can produce a dramatic variance in lux readings).
5. If you use a phone app, make sure you always use the same phone and application (use the phone as a measurement tool, not lab equipment).
6. Record your readings. You are looking for a pattern, not perfection (i.e. “my corner is usually 60-120 lux, measured at midday”).

Interpreting Your Lux: What is A True Low Lux Corner?

Below you will find various ranges that represent practical indoor classifications of foliage houseplants. These are not definitive biological limitations; they’re decision boundaries to help you determine what types of plants to select and to establish your growth expectations.

Due to less light, plants will continue to use water at their slower rates, so the number one killer of a plant in a corner with little or no light is usually due to over-watering the plant rather than due to the plant receiving enough fertilizer.

Definitions of a low-light corner plant that “tolerates” low light

Many people state that when a plant will “tolerate” low light, it means that it does not die quickly. It does NOT mean that they will be able to grow quickly or that they will look perfect. When you select plants to grow in areas of low-to-medium (150-300 lux) light, generally there are a few basic types of options: (1) those that perform well in brighter light conditions (>300 lux), (2) those that perform solely in lower light levels (i.e. <300 lux), and (3) those that can tolerate either.

To find out what type of light your indoor environment offers, first look at the light coming through the windows of your space. A “window” is an opening in a wall that lets sunlight into your home; usually the amount of natural illumination from any outdoor cheeriness, sun, or glare will tell you how much light is available. Therefore, check to see if the sun will rise on the eastern corner of your house or apartment (there may not be as much stable illumination from the south, west, or north), and if it does, that is considered a low-light source (L, d > 50 lux). If it does not, that is considered med-light (ML, d > 300 lux) illumination. Next check to see if your window is located in a sunny location. If so, you are getting plenty of light. If you are fortunate enough to have a south-facing window, consider it a high source of light (H, d > 1,000 lux).

Also be aware of specific growing characteristics of several plants, such as snake plants and ZZ Plants being low-light survivors. Plenty of easy-care plants can be grown in dim light (e.g. Heartleaf Philo, Pothos), while others may need more than just moderate light to grow. Keep in mind that anything below 100-150 lux will have extreme limitations regarding growth rate.

This means that you have limited options for adding green to low-light spaces without supplemental illumination. Generally speaking, you can expect your best elliptical growth with Snake, ZZ, Cast Iron, Epipremnum aureum (Pothos), Heartleaf Philodendron, Aglaonema, and/or Spathiphyllum (Peace Lily). However, for (1) addition of grow lights to add light to dimly lit areas or (2) accepting many plants to survive but not showing optimal characteristics. To try to provide additional sources of growing light for lower-light plants growing with grow light bulbs (30-50W surface mounted), you could use window coverings like sheers or shades to block out as much light as possible. – The biggest potential disappointment here will be; the majority of variegated plants, most palms, and the majority of flowering (house) plants due to the fact that bloom production requires a lot of light to complete.

Creating a brighter corner (6 – 12 ft. corners) without remodeling

1. Move your plant (cheap upgrade): you will notice (due to increase of lux) the closest you are to the window.
2. “Open” your “sky view”: move plant away from large furniture, avoid placing your plant behind something that it won’t have an unobstructed view of the sky.
3. Use brighter reflective surfaces: having a bright surface behind your plant (e.g. a white wall or white decorative panel) will cause a reflective bounce of light to the surface of the plant.
4. Keep glass clean: having clean windows, buying the right screen/sheer material for your window, and being aware of the fact that screens/sheer etc reduce light (especially if there is snow on the ground and no sun), will help your plants get as much light as possible.
5. Get a small grow light with a timer in case of truly dark spots: this is the most reliable way to increase the amount of light your plants will receive. Aim the light at the plant’s canopy instead of at the room. Start with 8-12 hours/day and adjust time as necessary based on your plant’s response.

Common low-light corner mistakes (and their quick fixes)

• Overwatering: Water less in low light, and allow the soil to dry more deeply between watering for drought-tolerant plants (snake/ZZ).
• Variegation won’t stay: Plants that exhibit variegation may revert to green in low light. Track patterns by increasing lux or using a growing light.
• Not rotating: Plants will lean toward the lightest direction. Rotate your plant every ¼ turn each week or bi-weekly to create an even growth.
• Measuring at the wrong time: A single reading at midday will definitely not show you how much light your plants are getting. If you are getting significantly dimmer light at your house in the morning and in the afternoon, the amount of light you received throughout the day will be low.
• Seasonal swings: Light levels in winter can be dramatically lower than at other times of the year in many U.S. homes, so if you are seeing decline in your plants in December or January check the lux levels again around that time.

Frequently Asked Questions

Bottom line: Measure light intensity (lux) to determine which plants to select

If you are located six to twelve feet from a window, you may be surprised at the amount of low-light corners (100 or fewer lux). If you measure provided lux levels of 100 or less, you can expect to be able to successfully grow plants but if you measure provided light levels of 10 or less, you will most likely need to have supplemental light or it will not be practical to have a plant in your space.

(*Note: This publication for general educational purposes only. Individual plant performance is influenced by numerous environmental factors (i.e. watering, potting mixture, temperature, insects, etc.) – When in doubt, test light, observe for growth, and adjust your light source as necessary to provide for optimum plant growth).