Soil & potting mix
Best soil for Begonia sizemoreae (Begonia sizemoreae)
Also called Sizemore's begonia.
More about begonia sizemoreae
About Begonia sizemoreae
Begonia sizemoreae · also called Sizemore's begonia · houseplant
Begonia sizemoreae, now treated as a form of B. longiciliata, is a fuzzy-leaved rhizomatous begonia from northern Vietnam. Its broad green leaves are fringed with long white hairs and often flushed bronze. Fast-growing and forgiving for a jewel-type begonia, it thrives in warm, humid, brightly shaded conditions and propagates readily.
Preferred mix: Light, organic, free-draining begonia mix
Watch for — Crown or rhizome rot: Overwatering or a soggy crown rots the rhizome. Use airy mix, water only when the surface dries, and keep the rhizome on the surface, not buried.
Why begonia sizemoreae needs this mix
Begonia sizemoreae wants a light, fine, evenly moist mix — soft-rooted and crown-sensitive, it suits an airy 1:1:1 blend, not heavy compost.
- Begonia sizemoreae has fine, shallow roots and a crown that rots if it sits wet, so the mix must be light, airy and only evenly moist.
- Equal parts compost, perlite and vermiculite give steady moisture and plenty of air at once — the balance this plant flowers on.
- A heavy, dense mix smothers the fine roots and is the usual reason it sulks and refuses to bloom.
For the full picture on what makes up a good mix, see our guide to the main types of soil and potting media — it explains why each ingredient above behaves the way it does.
What goes wrong with the wrong mix
The wrong soil is one of the most common reasons begonia sizemoreae struggles, and the damage often shows up weeks later as a watering problem. For this species specifically:
- Heavy, water-holding compost rots begonia sizemoreae's crown and fine roots — the plant goes limp and mushy at the centre.
- A coarse, gritty cactus-style mix dries too fast and the fine roots desiccate.
- Burying the crown when potting (rather than keeping it just at the surface) causes rot even in a good mix.
Using heavy compost and burying the crown. Begonia sizemoreae wants a light 1:1:1 mix with the crown sitting right at the surface.
pH — does it matter for begonia sizemoreae?
Begonia sizemoreae is not fussy about pH — a slightly acidic to neutral mix (around pH 6.0-7.0), which a standard peat-free compost provides, is perfectly fine. No testing needed.
If you want to check or adjust it, the soil pH guide walks through testing and the safe ways to nudge a mix more acidic or more alkaline.
DIY mix vs a bagged one
A decent bagged houseplant compost works for begonia sizemoreae as long as you mix in perlite for air. The simple DIY ratio above is cheap and more reliable than a budget bag alone.
Drainage and the pot
Use a small pot with a drainage hole and water from the bottom to keep the crown dry — wet leaves and a wet crown are this plant's main enemies.
Refresh begonia sizemoreae's mix every 18-24 months; even good compost slumps and compacts, and fresh, airy mix is often the simplest fix for a tired plant. When the time comes, our repotting guide for begonia sizemoreae covers the timing and technique step by step.
Begonia sizemoreae soil — frequently asked questions
What is the best soil mix for begonia sizemoreae?
1 part peat-free houseplant compost : 1 part perlite : 1 part vermiculite. Begonia sizemoreae has fine, shallow roots and a crown that rots if it sits wet, so the mix must be light, airy and only evenly moist.
Can I use normal potting soil for begonia sizemoreae?
Heavy, water-holding compost rots begonia sizemoreae's crown and fine roots — the plant goes limp and mushy at the centre. A decent bagged houseplant compost works for begonia sizemoreae as long as you mix in perlite for air. The simple DIY ratio above is cheap and more reliable than a budget bag alone.
Does begonia sizemoreae need a special pH?
Begonia sizemoreae is not fussy about pH — a slightly acidic to neutral mix (around pH 6.0-7.0), which a standard peat-free compost provides, is perfectly fine. No testing needed.
Should I buy a bagged mix or make my own for begonia sizemoreae?
A decent bagged houseplant compost works for begonia sizemoreae as long as you mix in perlite for air. The simple DIY ratio above is cheap and more reliable than a budget bag alone.
How often should I refresh the soil for begonia sizemoreae?
Refresh begonia sizemoreae's mix every 18-24 months; even good compost slumps and compacts, and fresh, airy mix is often the simplest fix for a tired plant. Use a small pot with a drainage hole and water from the bottom to keep the crown dry — wet leaves and a wet crown are this plant's main enemies.
Keep reading
- Begonia sizemoreae care — the full brief (light, water, humidity, problems, pet safety)
- How often to water begonia sizemoreae — the schedule the mix feeds into
- Repotting begonia sizemoreae — when and how to refresh the mix
- Soil pH guide — test it and adjust it safely
- Should I water my plant? The simple check first
- Overwatered plant — signs and recovery
- Root rot — how the wrong soil starts it, and how to save the plant
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