Repotting guide

When & how to repot Black Fang Begonia (Begonia 'Black Fang')

Also called Black Fang begonia, Black Fang eyelash begonia.

More about black fang begonia

About Black Fang Begonia

Begonia 'Black Fang' · also called Black Fang begonia, Black Fang eyelash begonia · houseplant

Begonia 'Black Fang' is a striking eyelash begonia (Begonia bowerae hybrid) distinguished by its very dark, near-black, deeply lobed leaves edged with fine white eyelash hairs and accented by bright green markings along the veins, giving it a dramatic gothic appearance. It is compact and relatively easy to grow in moderate indoor conditions, producing dainty pale pink flowers in late winter that contrast beautifully with the near-black foliage. As with all rhizomatous begonias, the paramount care rule is to avoid overwatering, since the shallow rhizome is extremely sensitive to soggy compost. Toxic to cats and dogs per the ASPCA.

Mature size: 15–25 cm tall and 20–35 cm wide in a suitably wide, shallow container.

Watch for — Rhizome rot from overwatering: The creeping rhizome is the most vulnerable part of this plant; if the compost stays wet for extended periods the rhizome turns soft and brown — repot immediately into dry compost, cutting away affected sections with a clean blade.

How to tell black fang begonia needs repotting

Repotting on a calendar is less reliable than reading the plant. For black fang begonia, watch for these signs:

Roots growing out of the drainage holes, or the rootball lifting the plant proud of the rim.
Soil that has shrunk away from the pot sides and no longer holds water.
The pot is unstable because the plant has grown top-heavy.
Old, compacted, broken-down mix that stays wet too long — for a succulent that is a rot risk, so refresh it even if the pot size is fine.

For the underlying biology of a pot-bound root system and why it stalls a plant, see our guide to spotting and fixing a root-bound plant.

How often to repot black fang begonia

Every 2–3 years, into bone-dry mix. Black Fang Begonia's growth habit — low-growing, spreading rhizomatous begonia with a creeping rhizome producing a mound of angular, deeply lobed, near-black leaves with contrasting vein patterns. — sets the pace. Begonia 'Black Fang' is a striking eyelash begonia (Begonia bowerae hybrid) distinguished by its very dark, near-black, deeply lobed leaves edged with fine white eyelash hairs and accented by bright green markings along the veins, giving it a dramatic gothic appearance. It is compact and relatively easy to grow in moderate indoor conditions, producing dainty pale pink flowers in late winter that contrast beautifully with the near-black foliage. As with all rhizomatous begonias, the paramount care rule is to avoid overwatering, since the shallow rhizome is extremely sensitive to soggy compost. Toxic to cats and dogs per the ASPCA.

What size pot to step black fang begonia up to

Use a pot only one size up — or even the same pot with fresh gritty mix if the roots have room. Black Fang Begonia stores water and rots in a large pot of slow-drying soil. A tight terracotta pot that dries fast is far safer than a generous plastic one. Never up-pot a succulent by several sizes.

Not sure of the exact diameter? Our pot size calculator takes the current pot and root spread and tells you the right next size — it deliberately recommends a single step up, never a big jump.

The best time of year to repot black fang begonia

Spring or summer, while black fang begonia is in active growth and warm, is best — roots recover fastest then, and the plant is not sitting in cool damp soil. Avoid repotting a succulent in winter dormancy.

Step-by-step: repotting black fang begonia

Repot dry. Do not water black fang begonia for several days first. Working with dry roots and dry mix dramatically lowers the rot risk for a succulent.
Pick a snug, fast-draining pot. Choose terracotta one size up at most, with a drainage hole. Have gritty gritty, free-draining potting mix ready.
Tip it out and clean the roots. Slide the plant out, crumble off the old soil, and trim any black, mushy or dead roots with clean snips.
Pot into dry mix. Set black fang begonia at its original depth in dry gritty mix, firming gently. Do not bury the stem deeper than it was.
Wait a week before watering. Leave it completely dry and out of harsh sun for about 7 days so any damaged roots callus. Only then water lightly.

Aftercare

Keep black fang begonia completely dry and out of fierce sun for about a week so any nicked roots callus before they meet moisture; watering a freshly repotted succulent is the classic way to rot it. Then resume the normal lean, dry rhythm. Do not fertilise for about 3 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for black fang begonia

Black Fang Begonia wants gritty, free-draining potting mix. A 1:1 mix of peat-free compost and perlite in a shallow, wide pot (to suit the creeping rhizome) works well; rhizomatous begonias do better slightly underpotted than in oversized containers that hold excess moisture. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting black fang begonia — frequently asked questions

How often should you repot black fang begonia?

Every 2–3 years, into bone-dry mix for black fang begonia. Repot black fang begonia every 2–3 years into a snug pot of gritty, free-draining potting mix, ideally in spring or summer. Let it sit in dry soil and do not water for about a week afterwards so any nicked roots can callus. Over-potting and watering straight away is what rots succulents.

What size pot does black fang begonia need?

When is the best time of year to repot black fang begonia?

Should you water black fang begonia after repotting?

No — not straight away. Repot black fang begonia into dry mix and wait about a week before the first watering so any damaged roots callus over. Watering a freshly repotted succulent is the single most common way to rot one.

Should you fertilise black fang begonia after repotting?

Not immediately. Wait about 3 weeks after repotting black fang begonia. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.