How to Grow and Care for Begonia Plants

Begonia is a vast genus of flowering plants with over 2,000 species native to tropical and subtropical regions. Their diversity offers a wide array of forms, making them popular for different environments. Gardeners appreciate begonias for their colorful flowers and dramatic foliage, using them as vibrant outdoor bedding plants and striking indoor ornamentals.

Major Types of Begonias

Understanding the major classifications helps in selecting a plant and providing the right conditions. These groups are defined by their root structure or growth habit. While hybridization can blur the lines, most common begonias fit into one of four main categories.

Rhizomatous begonias grow from a thick stem, or rhizome, that creeps along the soil surface. This rhizome serves as a storage organ for water and nutrients, from which both roots and leaves emerge. These plants are prized for their spectacular foliage, which comes in a variety of shapes, colors, and textures. Cultivars in the Rex group, for example, can display metallic sheens, spiral patterns, and vibrant shades of green, red, purple, and silver.

Tuberous begonias are cultivated for their large, showy flowers that appear in a brilliant spectrum of colors. They grow from round, flattened tubers that act as underground storage organs, allowing the plant to go dormant in winter. Because they are frost-tender, they are often grown as annuals in garden beds and containers. The tubers can also be dug up in the fall, stored in a cool, dry place, and replanted in the spring.

Cane begonias are named for their upright, segmented stems that resemble bamboo and include the popular “Angel Wing” varieties. This group is grown for both its attractive, wing-shaped foliage and its clusters of flowers. The leaves are often asymmetrical and can be speckled with silver spots or feature colorful undersides. Cane begonias can grow several feet tall, making them impressive specimen plants.

Wax begonias (Semperflorens) are fibrous-rooted plants used as bedding annuals. They have a mounding growth habit, glossy leaves, and a profusion of small flowers in shades of white, pink, or red. The leaves can be green, bronze, or reddish-brown, adding to their appeal. These tough begonias bloom almost continuously throughout the growing season in mild climates.

General Begonia Care

Most begonias thrive in bright, indirect light rather than intense, direct sun. An east-facing window that provides gentle morning sun is ideal for indoor plants. Tuberous begonias grown for flowers can handle more sunlight to fuel blooming. In contrast, rhizomatous types with delicate foliage prefer shadier conditions to prevent leaf scorch, while wax begonias are tolerant of partial sun.

Begonias are susceptible to root rot, so proper watering is important. Water thoroughly when the top inch of soil feels dry, allowing excess water to drain completely. This “drench and dry” method ensures the roots receive adequate moisture without being suffocated. Water at the base of the plant to keep foliage dry, which helps prevent fungal diseases. Tuberous begonias require significantly less water during their winter dormancy.

Begonias require a light, airy, and well-draining potting medium to prevent water from pooling around the roots. A standard peat-based potting mix amended with perlite or vermiculite is a good starting point. This combination provides moisture retention while allowing for the good aeration needed by their fine root systems.

Reflecting their tropical origins, begonias flourish in high humidity and stable temperatures. To increase ambient moisture indoors, you can use a humidifier, set the pot on a tray of pebbles and water, or group several plants together. Protect them from drafts from open windows or vents, as sudden temperature fluctuations can cause stress.

During the spring and summer growing season, apply a balanced, water-soluble fertilizer at half-strength every two to four weeks. Tuberous begonias benefit from a fertilizer higher in phosphorus to support their large flowers. Foliage-focused types like rhizomatous and cane begonias do well with a formulation higher in nitrogen to encourage lush leaf growth.

Propagating Begonias

Propagating begonias is a straightforward process, with the best method depending on the plant type.

Stem cuttings work well for cane and wax begonias. Select a healthy, non-flowering stem and cut a 4- to 6-inch section just below a leaf node. After removing the lower leaves, place the cutting in a jar of water or directly into moist potting mix where it will root.

Leaf cuttings are effective for propagating many rhizomatous and Rex begonias. You can use a whole leaf with its stalk (petiole) attached, inserting the petiole into a moist rooting medium. Alternatively, cut a single leaf into several wedge-shaped sections, each containing a main vein. Place these sections on the surface of the moist mix, and with sufficient humidity, new plantlets will form at the vein locations.

Division is a reliable method for rhizomatous and other clumping begonias, best performed during repotting. When the plant is out of its container, carefully separate the root ball and rhizome into smaller sections. Ensure each new piece has at least one growing point. These divisions can then be potted individually to grow into new, full-sized plants.

Common Pests and Diseases

Powdery mildew is a frequent fungal disease appearing as a white, dusty coating on leaves and stems. This problem is often caused by poor air circulation combined with high humidity. To manage it, improve ventilation, avoid wetting the leaves when watering, and promptly remove affected foliage. For persistent cases, a fungicide formulated for ornamental plants may be necessary.

Sucking insects like mealybugs and aphids can infest begonias, feeding on sap and causing distorted growth. Mealybugs appear as small, white, cottony masses, often hiding in leaf axils and on the undersides of leaves. Aphids are small, pear-shaped insects that cluster on new growth. Both can be controlled by dabbing them with a cotton swab dipped in rubbing alcohol or by spraying the plant with insecticidal soap.

Root rot is a serious condition resulting from overwatering and poorly draining soil. When roots are deprived of oxygen in waterlogged conditions, they decay and cannot absorb nutrients. Above-ground symptoms include wilting and yellowing leaves. To confirm, inspect the roots; healthy ones are firm and white, while rotted roots are brown and mushy. If caught early, a plant might be saved by trimming away affected roots and repotting in fresh, dry soil.

Begonia Toxicity

Pet owners should be aware that all parts of the begonia plant are toxic to cats and dogs. The toxicity is from soluble calcium oxalates, which can cause oral irritation, drooling, vomiting, and difficulty swallowing if ingested. The highest concentration of these compounds is in the plant’s underground tubers.