Begonia subnummularifolia

A creeping Begonia from northern Borneo

Begonia subnummularifolia is native to northern Borneo and was described from Banggi Island off Sabah.

Its creeping stems travel across the humid forest surface beneath filtered light, rooting through moss, leaf litter and other loose material close to the ground. Warm air and regular moisture are matched by airflow and rapid drainage through the shallow root zone.

Care for rhizomatous foliage growth

Watering

The small shallow root system should be watered when its surface starts to dry, using a gentle complete soak that drains freely instead of frequent surface misting.

Substrate and roots

The root structure of Begonia subnummularifolia is a compact network of delicate roots close to the substrate surface. Use a shallow ventilated pot only slightly larger than the roots, keeping the stem or rhizome at the surface.

Light

Give Begonia subnummularifolia a position near a bright north or east window, or under a suitable grow light in a ventilated cabinet where no direct sun reaches the leaves. Weak light reduces its definition by weakening growth, while harsh sun damages the surface without improving it.

Temperature

Keep both foliage and pot away from night-time glass chill and air-conditioning outlets.

Fertilising

Apply a very dilute complete foliage or orchid fertiliser to Begonia subnummularifolia only during active growth. Reduce the dose when light falls, the pot stays wet longer or fresh potting mix already contains fertiliser.

Repotting

Give Begonia subnummularifolia a new pot when fine roots occupy the shallow pot, the growing point reaches the rim, moisture becomes uneven or the substrate packs down. A fine Begonia root system performs best without a large volume of unused substrate.

Common concerns with Begonia subnummularifolia

Tiny coin-shaped leaves cup or wilt

Check the newest green leaves and feel the mix around the roots. A light, dry pot usually needs water. If the leaves stay limp in wet mix, inspect the fine roots and stems. Several tightly distorted or scarred leaves need a close pest check.

Fine creeping stems reach the pot rim

The stems naturally root as they extend and can form a dense mat beyond the original centre. Guide firm growth onto fresh surface mix in a wider shallow pot. Remove any dark soft section before it crosses the mat.

Water-soaked spots on round leaves

A genuine lesion looks glassy or soft and enlarges beyond the normal green surface. Remove the affected leaf, keep splashes off the mat and inspect the shared fine stem if neighbouring leaves begin to loosen.

Softening along one edge of the creeping mat

Trace the damage along the slender stems and cut back to firm green tissue. Root an unaffected outer tip on fresh mix and clear dead miniature leaves from around the surviving growth.

Begonia subnummularifolia is toxic to people and pets

• Keep this plant away from children, cats and dogs.
• The roots and rhizomes contain the highest levels of soluble oxalates, and the sap can irritate skin.
• Chewing may cause mouth irritation, drooling, vomiting or stomach pain. Contact a veterinarian or medical professional if symptoms develop.

How did Begonia subnummularifolia get its name?

Begonia honours Michel Bégon. The name subnummularifolia combines sub-, somewhat or almost, with nummularifolia, coin-leaved.

Carl Linnaeus established the genus Begonia in 1753 in Species Plantarum, page 1056.

Elmer Drew Merrill first described Begonia subnummularifolia in 1926 in Philippine Journal of Science 29: 403.