The rubber plant is a popular houseplant, thanks to its large, waxy leaves and sturdy stalks. Native to tropical rainforests, the rubber plant isn’t picky about its water, soil, and fertilizer requirements. However, creating the ideal lighting conditions for this plant can be tricky.
A rubber tree needs 6 to 8 hours of medium to bright, indirect light daily indoors. It can’t tolerate harsh direct sunlight. However, the variegated cultivars of rubber need more light to maintain their colors. While a rubber tree can survive in low light conditions, it won’t thrive.
Keep reading to explore how much light is too bright for your rubber plant and more on indirect light. I’ll also explain how you can measure the intensity of light entering your house using a light meter or smartphone and a light-measuring app. By the end of this article, you’ll know how to find the ideal spot for your rubber tree.
The Sunlight Requirements of Rubber Plants
Rubber plants are natives of rainforests where they grow as the understory, shaded by the foliage of the trees towering above them. They receive dappled sunlight. Bright, direct sunlight can burn their leaves.
When grown indoors, rubber plants need sunlight similar to their native environment. These plants thrive under medium to bright, indirect sunlight.
Indoor rubber plants do best when placed near a south-facing window covered by sheer curtains that diffuse the sunlight or near an east-facing window where they receive morning light. Ensure that the plant is about 5 feet (1.5 m) away from the windows.
If you put your rubber plant next to a window, hang a sheer curtain or drape between the glass and plant for protection from direct sunlight.
However, if you only have a northern window or there are buildings or structures blocking the sunlight, you can grow rubber plants under artificial light. They do well under fluorescent light with an intensity of between 250 and 1000 foot candles switched on for 12-14 hours a day.
In simple terms, you can switch on a 40-watt lamp and position the rubber plant about a foot (30 cm) below it. The farther the lamp is, the lesser light intensity the plant receives. In that case, you’ll need two lamps.
In addition, you will need to consider the following tips when growing a rubber tree indoors:
- Move your plant to another suitable cooler spot in the house if the temperature near the window goes above 75 °F (24 °C).
- Ensure you move the plant away from drafty windows in winter.
- Learn about the signals your plant sends out if it receives too little or too much light, such as becoming leggy, wilting, or burn spots.
Understanding Bright, Indirect Light
If you’re a newbie plant parent or don’t have much experience growing plants indoors, you might wonder what bright, indirect light is.
Bright light is light that casts a somewhat distinct shadow with fuzzy edges, while indirect light for a plant is light that hits another surface before landing on the leaves. You can read by bright light without supplemental lighting.
Indoor rubber plants need bright, indirect light to thrive. You can create bright, indirect light by shielding south and west-facing windows with sheer or see-through curtains that filter the sunlight before it reaches the plants.
Here’s how you can determine if you have bright, indirect light in a sunny spot in your house:
- Carry out the activity around noon when the sun shines brightly through the window.
- Choose the location where you want to place the plant.
- Place your hand between the sunlight coming through the window and the opposite wall.
A bright, direct light will cast a dark and sharply-defined shadow with stark contrast on the opposite wall. On the other hand, bright, indirect light casts a more or less distinct shadow with fuzzy edges. As for low light, it creates a very faint shadow with an indistinct outline.
If you aren’t confident about doing an eye check, you can use a light meter to determine the intensity of the light coming in through the window.
How to Measure the Intensity of the Light Entering Your Home
It’s challenging to keep a plant healthy and happy when it’s not growing in its natural habitat. But you can tweak your watering schedule, the soil mix, and the fertilizer to mimic the conditions in your rubber plant’s natural environment.
However, you can’t change the amount of light that shines in through the window and hits your plant. So you must determine the intensity of the light entering your house and choose the ideal spot for your plant.
Use a Light Meter Device
A light meter measures the intensity of light and expresses a value in foot candles (FC). Some devices use lux as the unit.
A value of 50-250 FC indicates low light and needs 10-15 watts of artificial light per square foot. Medium-light is between 250 and 1000 FC at mid-day or more than 15 watts per square foot.
An indoor rubber plant thrives in the medium to bright light range. However, if the light intensity is on the lower end of the medium light spectrum, it may drop a few leaves.
If you’re used to measuring in foot-candles but your machine gives a value in lux, use this conversion formula:
1 lux = .0929 foot-candle
To find out the value in foot-candles, multiply the lux value displayed on the meter by .0929.
A light meter is a simple and inexpensive device that helps you keep your indoor plant babies flourishing in optimal light. You can get light meters at your garden center or online.
Use a Light-Measuring App
You can also use a light-measuring app and your smartphone camera to determine light intensity. Download a light-measuring app on your phone.
Here’s how you can use a light-measuring app and your smartphone camera to measure the intensity of light for your indoor rubber plant:
- Choose the unit (FC or lux) in the light-measuring app on your smartphone.
- Select the “Outdoor” setting.
- Point the camera of your phone towards the light. If using a light meter, hold the device close to the leaves of the plant and point the sensor in the direction of the light.
- Tap the SUN icon. This icon may look different on different app interfaces. However, the button will have some image that indicates illumination.
- Note the measurements for various areas in your house before choosing a spot to place your rubber plant.
You must remember that the amount and intensity of sunlight entering through a window can differ throughout the day and across seasons. For instance, the light entering through a south-facing window during winter is less intense than in summer.
You may have to move your rubber plant around to accommodate the change in light intensity.
Can Rubber Plants Tolerate Low Light?
Rubber plants can tolerate low light. However, these plants flourish if they receive bright, indirect light for six to eight hours daily. If kept in low light for too long, the plant’s leaves will fade in color and may curl.
Rubber plants show stunted growth when kept in low-light conditions. Under prolonged low light, the leaves of variegated rubber trees will become dull green.
Rubber plants grow on the floors of rainforests. They’re protected from the sun’s direct rays by a canopy of foliage. However, the rainforest canopy is very high and lets in filtered sunlight, so rubber trees don’t do well in dark spots.
A rubber plant cannot thrive in too much direct light, either.
Look out for the following signs that your plant is receiving too much light:
- It has brown or sun-burned spots on the leaves.
- The leaves lose color.
- The leaves become dry and crisp.
- Your rubber plant leaves droop.
- The plant fails to thrive and shows signs of wilting.
Rubber plants are resilient. Your plant will perk up as soon as you move it to a spot where the light is optimal. Ensure the plant remains hydrated, and make sure the soil is moist.
Rubber trees originated in the warm, tropical rainforests of the world. So, many plant growers mistakenly think these plants need intense sunlight to survive.
Rubber trees grow as understory in the warm jungles and receive dappled sunlight that filters through the overhead leafy canopy. Therefore, you must keep your indoor rubber tree in a location that receives bright, indirect light.
Watch for signs of too much or too little light. That way, you’ll know when to move your plant to another location with more suitable lighting conditions.