How to Grow Rubber Plants Indoors or Outdoors
Rubber plants, which were popular in the 1970s, are making a comeback in both commercial and residential spaces.
What are Rubber Plants?
Rubber plants (Ficus elastica) are trees that are native to Southeast Asia. They are not related to the rubber trees (Hevea brasiliensis) from which rubber is derived, but they do contain a latex like substance. Similar to the latex derived from H. brasiliensis, the latex in F. elastic is toxic if ingested. It also irritates skin and eyes, so be very careful when handling these plants. Wearing gloves is a good idea.
Rubber plants are only hardy in zones 10 through 12. They are related to banyan trees and grow aerial roots like banyans. In the wild, rubber plants will grow to 100 feet tall. When grown indoors, in containers, they normally do not get any larger than 10 feet.
The trees have broad oval leaves, about 12 inches long, that are very shiny. Most are dark green, but newer cultivars have been developed that have variegation. Tiny white flowers are common when the trees are grown outdoors, but rare when grown indoors. The trees will not develop fruit outside of their native range because the flowers are pollinated by a single species of fig moth that is only found in Southeast Asia.
How to Grow Rubber Plants Outdoors
Outdoors, rubber plants grow in full sun or partial shade. They prefer heat and humidity, so it is a good idea to cover the roots with a 2 inch layer of mulch which will keep the soil moist longer. Water your trees when the top inch of soil becomes dry. Morning watering is the best. That way any water that splashes on the leaves will have time to dry before evening. Water left on the leaves overnight is an invitation to diseases like downy mildew. You can cut back on watering during the winter when the trees are resting. During the growing season, fertilize every three months with a balanced fertilizer such as 10-10-10. Always remove any dead leaves or branches immediately to avoid disease or insect infestation of the dead material.
How to Grow Rubber Plants Indoors
Growing rubber plants indoors is a little trickier. They need to be kept out of direct sunlight. A room with brightly filtered light is best. Putting your tree in front of a sunny window risks burning it on a hot summer day. The glass refracts the light, making it hotter. Too hot for the poor tree. My rubber plant grew in front of an east facing window in a tall stairwell that easily accommodated its height.
Be sure to keep your tree well-watered but not soggy. Fertilize with a balanced fertilizer such as 10-10-10 every two months. More frequent fertilizing is necessary when you grow any plant in a container because when you water, the nutrients in the soil are leached out of the drainage hole. They need to be replaced more frequently than when plants are growing in the ground.
You will need to repot your tree every year into a larger pot until it has reached the height that is best for your space. Use a pot that is 2 inches larger than the one it is in currently. Here’s a tip for cat lovers. My cat loved that big pot that my rubber plant grew in. He thought the open soil made the perfect litter box! I covered the soil with large stones. The stones allowed water to get to the soil while making it uninviting to my cat.
How to Grow Rubber Plants From Cuttings
Rubber plants are extremely difficult to propagate. Most people just buy the plants rather than trying to grow them from cuttings. If you want to attempt it, the best way is by using a leaf-tip cutting. This is a cutting made from one of the large leaves, rather than from a branch. As the name implies, cut off a piece of a leaf, generally the last 2 inches at the tip. Dip the cut in rooting hormone and then bury the cutting an inch into the soil in a container.
Cover the container with a plastic bag to create humidity and place it in indirect light in a room the is between 65⁰F and 72⁰F. Keep the soil evenly moist. Roots should develop in 6 to 8 weeks.
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