Rubber plant

Identification and origin

Ficus elastica belongs to the fig family, Moraceae. It is native from the eastern Himalaya (Nepal, Assam, Bangladesh) through mainland Southeast Asia (Myanmar, Thailand, Laos, Vietnam and south-central China) to the Malay Peninsula, Sumatra and Java. It often starts life as an epiphyte perched on another tree. Mature trees form a broad crown and, like banyans, send down aerial roots that reach the ground and become new trunks. In its native habitat it grows 49–98.5 ft tall.

The leaves are large, elliptic, thick, stiff and leathery, a glossy dark green, and can exceed 12 in long by 3–6 in wide; the midrib, raised on the underside, ranges from pale to reddish. Each new leaf unfurls from a pink to purplish sheath (the stipule), which is quite ornamental. The milky sap was used to make a low-grade rubber in the early 1900s, hence the name. The small, oblong figs, borne in pairs and about 1 in long, are rarely seen outside the native range: they only set fertile seed where the pollinating insect lives.

Indoors it typically grows 2–10 ft tall. There are many cultivars: ‘Decora’ (larger leaves with an ivory midrib), ‘Robusta’, ‘Burgundy’ (nearly black leaves with red midveins and red new growth), ‘Variegata’ (narrow leaves edged in yellow), ‘Tineke’, ‘Doescheri’ and ‘Tricolor’.

Light

Bright indirect light or part shade, with protection from afternoon sun. It grows best in morning light from an east window. It adapts to lower light, where it needs less fertilizer. Unfiltered direct sun can damage the leaves, although variegated forms can handle a couple of hours of sun indoors. Once it is in a good spot, leave it there: it does not like being moved.

Watering

Water thoroughly, then let the surface of the mix dry slightly before watering again; many rubber plants do best when the top half of the root ball has dried. The pot must have drainage holes, and the saucer should be emptied after every watering. Constantly soggy soil rots the roots and causes leaf drop, and so does prolonged dryness. From fall to late winter the plant rests, so cut back watering noticeably.

It prefers humid air but tolerates the dry air in most homes. In summer, occasional misting, a tray of moist pebbles or grouping it with other plants helps. Wipe the dust off the leaves with a damp sponge or soft cloth: they stay attractive and the plant stays healthier.

Potting mix

A well-drained, soil-based houseplant mix. During active growth in spring and summer, feed with a water-soluble houseplant fertilizer every two weeks; feed less often if the plant is in a dim room.

Temperature

Ideal conditions are around 61–64 °F at night and 75–81 °F during the day. Avoid temperatures below 55 °F and sudden drops. Moving air is its weak spot: keep it away from radiators, heating and air-conditioning vents and doors to the outside, especially in winter. In the ground it is listed for USDA zones 9a–12b (winter lows around 19 °F), but it is only truly at home from zone 10.

Repotting

When needed, in late winter or early spring. Use a pot with drainage holes and a free-draining mix.

Pruning

Pruning in spring rejuvenates a leggy plant. Cutting back the main branches encourages bushier growth; leaving it unpruned gives a tall, narrow, tree-like form. Every cut bleeds sticky, milky sap, so wear gloves and protect the floor.

Propagation

From tip or stem cuttings, or by air layering. Seed is only an option with fertile seed, which is rare in cultivation.

Common problems

The same symptom can have several causes: check watering, light, humidity and air currents.

• Leaf drop: overwatering, underwatering, a drop in temperature or a blast of cold air. It is normal for an occasional bottom leaf to yellow and fall.
• Yellow or damaged leaves: improper watering, too little light or too much sun, dry air or air currents.
• Root rot: a mix that doesn’t drain quickly enough or watering too often.
• Pests: mealybugs, scale insects, thrips, spider mites and aphids.

Toxicity

Toxic to dogs, cats and horses: as in many Ficus, the milky sap is irritating. Chewed, it irritates the mouth and digestive tract (loss of appetite, drooling, vomiting, diarrhea), and on contact it can irritate skin. In people, too, it can irritate the skin or the stomach if swallowed. Keep the plant away from pets and from young children who tend to chew on plants, wear gloves when pruning it, and call a veterinarian if a pet eats any.