Begonia

One of the largest plant genera on earth, more than two thousand species from the world's tropics, grown for painted foliage and for flowers. They are not aroids, and they split into a few clear types, but one care rhythm carries across them. This guide covers the genus; the standout types and cultivars get their own cards.

Care at a glance

Origin & history

One rhythm, several types. Begonia is one of the largest genera of flowering plants, more than two thousand species (Plants of the World Online, n.d.). It is pantropical, native across the tropical Americas, sub-Saharan Africa, and southern and Southeast Asia. Despite the spread, most begonias want the same conditions of the forest understory they came from: warm, bright but shaded, humid, and never waterlogged.

Growers sort them by habit rather than botany. Cane types grow upright on jointed, bamboo-like stems and flower in hanging clusters. Rhizomatous types, which include the foliage-famous Rex begonias, creep along the surface on thick stems and are grown for their leaves. Tuberous types grow from an underground tuber and rest each year.

The core care is the same for all of them; what changes is how you stage the plant. Those differences, and the handful that change care, live on the species cards in this guide.

Care in depth

Light and warmth. Bright, indirect light suits the genus, with harsh direct sun kept off the leaves. Rex and other foliage types are happy in medium light, while cane and flowering types want it brighter to bloom well. Keep them warm, around 60 to 75°F (16–24°C), and clear of cold drafts; begonias are tender and dislike a chill.

Water and airflow. This is where begonias are won or lost. Keep the mix lightly moist but let the surface dry between waterings, and water at soil level rather than over the leaves, in the morning. Wet foliage and still, damp air invite powdery mildew and gray mold, so give the plant room to breathe. High ambient humidity is welcome, but raise it with a humidifier or pebble tray, not by wetting the leaves.

Substrate and nutrients. Pot in a light, airy, well-drained mix on peat or coir with perlite; begonias rot in heavy, wet soil. Rhizomatous and Rex types are shallow-rooted and do well in wide, shallow pots. Feed a dilute balanced fertilizer through active growth and ease off in the darker months.

Common problems & pests

What you see	Likely cause	What to do
White powdery patches on leaves	Powdery mildew (still, damp air)	Improve airflow; remove affected leaves; keep foliage dry.
Gray fuzzy mold, collapsing tissue	Botrytis (gray mold)	Cut out affected parts; more air; water at soil.
Soft, blackening stem base	Stem or root rot (too wet)	Let it dry; chunkier mix; take healthy cuttings.
Cottony white tufts	Mealybugs	Dab with 70% alcohol; repeat; spot-test soaps first.
Leaf tips and edges browning	Dry air or salt buildup	Raise humidity; flush the pot; steadier water.

In this genus

Each plant inherits the genus care above; the note is only what differs. Photos to come.