Lukuana Begonia Houseplant

An introduction

Begonia lukuana is an Asian begonia native to Taiwan, one of many begonias that grow on the island’s shaded, humid mountain slopes. It is grown as a foliage houseplant, valued for the fresh, lopsided leaves typical of the genus and for being easy to keep on a windowsill or shaded shelf. It is less familiar than many American and hybrid begonias, and suits growers who like species plants with a clear wild origin. Warm, moist and shaded conditions suit it best, matching the forest it comes from.

What it looks like

The leaves show the family’s usual asymmetry, with one side of the blade running lower down the stalk than the other. They grow in a low, spreading habit instead of on tall canes. Fresh to deep green and softly textured, they build into a leafy clump over a season. Small pale flowers, white to pink-tinged, open on slender stalks above the foliage in the warmer months. Each cluster carries separate male and female flowers, with the female flowers set on a small three-winged capsule that ripens the fine seed.

Its home ground

In the wild this begonia grows in the warm, wet forests of Taiwan, rooting in shaded, humus-rich ground where mountain mist keeps the air moist and the tree canopy filters the light. That habitat explains what it needs in a pot. Keep it warm, keep the air humid around the leaves, and give it bright light softened by shade.

Positioning for light

Give it bright, indirect light, such as an east or north-east window or a spot set back from a sunnier one. Direct summer sun through glass scorches the leaves and fades their colour. A dim corner draws the growth out thin and pale and spaces the leaves too far apart. A steady, well-lit place out of direct sun keeps the clump compact and the foliage healthy. Turn the pot from time to time so it grows evenly on all sides.

Watering

Water once the top couple of centimetres of compost have dried, soaking the root ball and pouring off any surplus so the pot never stands wet. The soft, thin leaves lose water faster than those of leathery-leaved begonias, so through spring and summer keep it evenly moist and do not let the clump wilt. In the darker, cooler months growth slows and the plant needs much less, with more of the mix drying between drinks. Its main enemy is cold, sodden compost, which rots the shallow roots, so water less whenever the room is cool. Water onto the compost rather than over the low crown of leaves.

Warmth and humidity

Hold it in steady warmth, above about 13 deg C and clear of cold draughts. It comes from Taiwan’s misty mountain slopes, so the dry air of a heated room browns the soft leaf edges quickly. Stand it on a tray of damp gravel, group it with other plants, or keep it in a naturally humid room such as a bright bathroom. Because the clump sits low and the leaves crowd together, keep a little air moving through it so damp does not turn into grey mould.

Feeding

Feed every couple of weeks through the growing season with a balanced liquid fertiliser diluted to half strength. That is enough to keep the leaves green and the plant growing steadily. Heavy feeding forces soft, weak growth, so a gentle regular dose works better than an occasional strong one. Stop feeding over winter, when growth pauses, and start again as new leaves appear in spring.

Propagation

Stem or basal cuttings root readily in spring and summer. Trim a healthy shoot below a joint and set it in warm, damp, open compost under cover, and roots should follow within a few weeks. A whole leaf, its veins nicked and pinned flat to moist compost in a covered tray, will raise plantlets from the cuts. Divide a crowded clump at repotting in spring, potting each piece into fresh mix. Fresh seed sown on the surface of damp compost germinates in warmth, though the seedlings are slow to reach a useful size.

Health and pests

Grown warm, humid and shaded, this begonia is usually healthy. Dry air brings on spider mites, which stipple the leaves and spin faint webs in the joints. Raise the humidity and rinse the foliage to keep them down. Mealybugs sometimes shelter in the leaf axils as white woolly tufts and can be wiped off with dilute alcohol. Grey mould can spread on leaves left cold and wet in still air. Yellowing lower leaves that drop away usually point to a root ball kept too wet and cold.

The year in outline

Spring brings fresh growth. Take cuttings, divide crowded plants and resume feeding.

Summer fills the clump with leaf and raises the pale white to pink-tinged flowers on their slender stalks. Water regularly, feed and hold the air moist.

Autumn slows the plant as the light drops. Water less often and taper off the feed.

Winter is a warm, quiet rest. Keep the clump off any chill, water sparingly, and let more of the mix dry out between drinks while growth has paused.

Frequently asked

Why are the leaf edges browning? The air is too dry. Stand it on damp gravel or move it to a more humid room, away from any heat source.

How much light does it want? Bright, indirect light. Keep it out of direct sun, which scorches the leaves, and out of gloom, which thins the growth.

How often should I water it? Once the top couple of centimetres have dried. The soft leaves need steadier moisture than a leathery begonia, so keep it evenly moist in growth and considerably drier through winter.

How do I propagate it? Set a stem or basal cutting into warm, damp compost, or pin a whole leaf flat on moist compost with its main veins nicked to raise plantlets from the cuts.

Is it safe around pets? Treat it as mildly toxic. The ASPCA lists begonias as toxic to cats, dogs and horses, because the insoluble oxalate crystals burn the mouth and cause drooling and vomiting. Keep it away from animals that chew the foliage.