Begonia ‘Black Mambo’ (Rex Cultorum Group; also ‘Dark Mambo’)

Leaf and rhizome care for foliage plants

Root care and leaf care

Keep the surface rhizome moving across a wide pot, without staking the petioles. Wait until an ageing leaf is fully yellow, then cut it at the base.

Watering

Water Begonia ‘Black Mambo’ (Rex Cultorum Group; also sold as Begonia ‘Dark Mambo’) when the upper layer of the substrate has dried and the lower shallow root zone still holds a trace of moisture. Check directly beneath the rhizome of the plant.

Light

Place Begonia ‘Black Mambo’ (Rex Cultorum Group; also sold as Begonia ‘Dark Mambo’) at an east window. A south or west window also works, provided hot sun does not reach the leaves.

Substrate and roots

Begonia ‘Black Mambo’ (Rex Cultorum Group; also sold as Begonia ‘Dark Mambo’) has a sideways-growing rhizome with fine feeder roots near the surface. Dense compost stays wet beneath the rhizome, while orchid bark used alone dries too unevenly.

Humidity and airflow

Most Rex begonias manage ordinary room air, but moderate to high humidity improves expansion of soft new leaves. Keep the dark velvety leaves away from direct heater air while they are soft and opening.

Repotting

Repot Begonia ‘Black Mambo’ (Rex Cultorum Group; also sold as Begonia ‘Dark Mambo’) when the rhizome reaches or circles the rim, roots fill the shallow pot, watering becomes uneven or the mix loses its open structure. Use the extra width to give the newest growth on the plant room, while the rhizome remains on the surface.

Common concerns with Begonia ‘Black Mambo’ (Rex Cultorum Group; also ‘Dark Mambo’)

Almost-black leaves are mistaken for necrosis

The velvety dark colour and red highlights are normal when the tissue is evenly coloured and firm. An irregular, translucent or papery patch that continues to expand is damaged tissue. Mark the edge of a doubtful area and monitor it; remove the leaf promptly if softness or spread confirms decay.

Wavy margins turn brown and crisp

The exposed ruffles lose moisture faster than the centre after dry air, a cold draught or an overly dry root ball. Check if the damage is confined to the edge. Stabilise the position and root moisture, trimming only dead tissue. Let the shallow rhizome drain well.

Dark leaves wilt in a wet pot

Very dark foliage can hide early yellowing, so lift the pot, smell the root ball and feel the rhizome. Remove the plant from stagnant mix, trim brown soft roots and set the surviving firm rhizome shallowly in a smaller, airy pot. A collapsing crown needs attention the same day.

New black leaves emerge bronzed and tight

Bronzing can be hard to see against this cultivar. Look for brittle young tissue, rolled edges and a run of misshapen leaves, which may indicate broad mites; silvery scratches and black dots fit thrips better. Isolate first, identify under magnification and treat the pest found.

Begonia ‘Black Mambo’ 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 get its name?

Begonia honours Michel Bégon.

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