Rubber plants (Ficus elastica) are easy-to-grow houseplants and low maintenance, have few problems, and tolerate a wide range of conditions—just not cold temperatures. For these reasons, they are good for beginners or those that feel “gardening challenged”, or good choices for tough indoor conditions such as in commercial and business settings.
This native of southern and southeast Asia is neither made of rubber nor used for it now, although a low grade of rubber was made from the sap in the early 1900’s. Most of the world’s rubber, instead, now comes from another rubber tree (Hevea brasiliensis). The genus name (Ficus) refers to the edible fig to which it is related, and the species name (elastica) to the white sticky sap. This sap may irritate the skin or stomach if eaten, so keep it away from pets and children that may ingest it.
Although growing 50 to 100 feet tall in its native tropics, with aerial roots that form trunks supporting the heavy limbs to the ground, indoors rubber plants generally grow from two to 10 feet tall. It has attractive, glossy and leathery leaves up to one foot long and to five inches wide. They are oval to oblong. Flowers and fruits are seldom seen on plants grown indoors.
While you may see it growing outdoors in full sun in southern Florida as a landscape plant, indoors it prefers bright indirect light and will tolerate low light. An ideal location is by a window that gets morning sun from the east.
Water regularly while it is growing—generally spring and summer—but don’t overwater. Let the soil dry to the touch before watering. If in doubt, don’t water. Under-watering is better than over-watering. Reduce watering when plants aren’t growing—generally, fall through winter. Make sure plants are in pots with drainage holes, and that pots don’t sit in saucers filled with water. Fertilize when plants are growing, according to the label directions on a product of your choice.
Rubber plants prefer humid air but will tolerate the drier air of most indoor environments. Also, they prefer warm temperatures— 60 to 65 degrees (F) at night and 75 to 80 degrees during the day is ideal. Yet they grow well at most temperatures above 55 degrees. Avoid a colder temperature than this, sudden temperature drops, or cold drafts such as near outdoor doorways.
Plants may grow tall and lanky indoors, particularly if grown with lower light levels. You can either support them with a stake or prune them back in spring as growth resumes to make them bushier. This is the time to repot them, too, if needed. If you cut them back, you can propagate new plants from the stem or tip cuttings, or by air layering.
Air layering is the process of stimulating new roots to grow on a stem while it is still attached, and is used on plants with thick stems or canes such as rubber plants. Notch the stem where you’d like roots to form, dust with a rooting hormone powder (available at full-service garden stores, or online), then wrap this area with a moist foam or sphagnum moss. Cover with plastic (held with twist ties) to maintain the moisture. Hopefully, after a few months, you’ll find roots growing and you can cut the stem below these, and pot. Use a houseplant soil (not garden soil) for potting, or repotting.
The main pest you may find on rubber plants indoors are white mealybugs. Wiping leaves periodically with mildly soapy water will keep these from multiplying, and will clean dust off that tends to accumulate on the large leaves. If leaves turn yellow and drop off, that is a sign the soil may be staying too wet. Leaves may just fall off, too, if plants receive too little light, cold drafts, or are in air that is too dry. Using a humidifier near plants will help them, as well as you if indoor humidity is really low.
While the species has dark green leaves, there are several popular cultivars (cultivated varieties) that you often find instead, some of which have been around since the Victorian era. ‘Decora’ has creamy white midribs contrasting on the dark green leaves. ‘Doescheri’ has variegated leaves that are cream and gray, with pink midribs. ‘Robusta’ has very large leaves up to 18 inches long, and tolerates low light well. ‘Rubra’ is perhaps the most commonly found cultivar, its young reddish leaves maturing to deep green with red edges. ‘Tricolor’ is just that, its green leaves with cream and pink patches.
Rubber plants, themselves, may help you indoors as they’ve been found to be one of the top “clean air” plants. In a famous study by Bill Wolverton during the 1980’s while he was with NASA, this plant was found to remove some chemical toxins from the indoor air, particularly formaldehyde. The latter can come from paper products, particle board, plywood paneling, and synthetic fabrics. His recommendation was to have at least two large (8- to 10-inch pots) for 100 square feet of space.
While other researchers, in subsequent studies, have questioned this effectiveness in homes compared to normal air exchange with outdoors, rubber plants may still help air quality in tight buildings. Similar to other houseplants, having these around can help with many psychological and physical benefits, too, such as reducing stress and improving moods. If you want a tough indoor plant that tolerates a range of conditions and stresses, including neglect, then the rubber plant may be a good choice if you have space for a medium to large plant.
Dr. Leonard Perry, Horticulture Professor Emeritus
University of Vermont