Inferior Rubber, Superior House Plant

Rubber tree as house plant
Rubber tree as house plant

The rubber plant that you see so often in corporate lobbies, doctors’ offices, living rooms and other large, bright, indirectly-lit rooms is a member of the family Moraceae, which includes mulberries and figs. Ficus elastica is native to the Himalayas, India, western Southeast Asia, and Indonesia. It has become naturalized in many other parts of the world including the Mediterranean, Caribbean, and even south Florida.

It was not the primary source of rubber before the petroleum era. That was Hevea brasiliensis, the Pará rubber tree, which, as its name indicates, is originally from Brazil, but through the 19th century was planted all over the tropics, particularly in Southeast Asia.

Both plants produce a latex material that can be processed into rubber, but that of F. elastica was inferior to that of H. brasiliensis. Latex is found in 10 percent of all plants in one form or another and seemed to have evolved independently many times. It has been shown to be a defense mechanism against herbivory. It is perhaps not a coincidence that latex allergies are common in humans.

Rubber tree as street tree in Brazil
Rubber tree as street tree in Brazil

F. elastica is popular because it is easy to take care of and grows to a relatively large size—8 or 9 feet—relatively quickly. There are dozens of websites that tell you how to take care of these plants. Its biggest problems are overwatering and too much direct sunlight.

As is common among tropical plants, F. elastica is actually fairly drought-tolerant. You should wait until the potting soil is dry to the touch before you give it more water. Then you should really soak it until the water begins to run out the bottom of the pot. It doesn’t like to sit in water, however, and the tray should be empties after the pot finishes draining. If it is over watered the leaves will turn yellow and drop off.

This particular fig likes bright light, but it should not be direct, as the plant does not like temperatures above 85 degrees F. Leaving the plant in bright sunlight will cause it to get stringy. Like a lot of figs, it doesn’t like to be moved around a lot, although some care sites recommend seasonal changes in location.

Ficus elastic flower
Ficus elastica flower

Although it gets to be a big house plant, this is nothing compared to its wild state, where it becomes a substantial tree 90 to 100 feet tall. It is also noted for developing, like the related banyan (another fig) it produces aerial and buttressing roots that hold up the limbs of the tree and give an architectural look.

Like all figs, F. elastica has an unspectacular flower that is pollinated by a local species of fig wasp. Where the wasp does not occur, e.g. Hawaii, the species can grow, but not reproduce sexually. Unless the flower is fertilized, it will not produce fruits.

The new leaves of the plant are first visible as curved, rose-colored spikes sprouting between existing leaves. Eventually the rosy sheath falls off and the deep green leaf unfurls.

The leaves of the rubber plant should be keep clean and moist. They should be wiped with a damp cloth if they get dusty and misted with warm water in the morning if the plant is being kept in hot, dry conditions (e.g. houses warmed by electric heat).

There is mixed information about how often rubber plants should be fertilized. One source recommends once a year in late March or early April. Other sites recommend more frequent applications. This may be related to whether or not the plant becomes dormant or not. Fall to late winter is considered to be the dormant season and watering should be reduced.