How to Grow Wax Begonia Indoors

potted begonia plant

The Spruce / Kara Riley

Begonia is a very large genus containing more nearly 2,000 annual, perennial, and woody shrub species native to tropical and subtropical climates around the world. The wax begonia group, categorized as Begonia x semperflorens or Semperflorens Cultorum Group, comprises varieties used primarily as bedding annuals, though they are technically warm-weather perennials. These fibrous-rooted plants have a compact, bushy mounded shape with flesh stems, dark green or bronze waxy leaves, and loose clusters of flowers that bloom all summer and into fall.

Wax begonia is one of the most popular bedding plants in landscaping. Innumerable flats of these sturdy plants are poked into the soil every spring to create lush beds of flowers. The reasons for this heavy use are obvious—they're durable, ever-blooming plants that provide sweeping color in single or double blooms.

Wax begonias are normally planted in the spring from bedding flats or potted plants started in a greenhouse environment. They can also be planted from seeds, though the plants are quite slow-growing at first, and it can take several months for them to mature to flowering plants. For this reason, seeds are usually started indoors about 12 weeks before the last expected frost.

While most people think of these exclusively as outdoor plants, in reality, wax begonias also make excellent indoor plants, where they become true perennials.

closeup of begonias
The Spruce / Kara Riley
top view of begonias
The Spruce / Kara Riley
 Botanical Name  Begonia (Semperflorens Cultorum Group) 
 Common Name  Wax begonia
 Plant Type  Herbaceous perennial (frequently planted as an annual)
 Mature Size  6–12 inches
 Sun Exposure  Full sun to part shade
 Soil Type  Moist, well-drained soil
 Soil pH  5.5–6.5 (slightly acidic)
 Bloom Time  Summer into fall
 Flower Color  White, pink, red, bicolors
 Hardiness Zones  10–11 (USDA); planted as annuals in most regions
 Native Area  South America
 Toxicity  Non-toxic to humans; toxic to animals

 Wax Begonia Care

As native to tropical regions, wax begonia is very well suited to warm, humid growing conditions. They will do best when given consistent moisture conditions, and they react badly to drought or extreme cold. Moderately rich, well-drained soil in a full-sun to part-shade location will allow these plants to thrive with little care.

Wax begonias are not difficult plants to grow indoors and can be included in a massed windowsill planting for bright indoor color. To keep the plants looking vibrant, pinch off old blooms and keep the plant free of brown and old leaves.

Light

In the garden, wax begonias prefer bright filtered sun, but they can grow well in full sun in all but the hottest and harshest climates. The bronze-leaved varieties tend to tolerate harsh sun a little better than the green-leaved varieties. If growing them indoors as potted plants, give wax begonias as much bright light as possible. East-, west-, or south-facing windows are best, as these exposures provide sufficient light.

Water

Planted in the garden, wax begonias will require a minimum of 1 inch of water per week. Applying a thick layer of mulch will help retain soil moisture between waterings. Indoor potted plants should be watered when the soil dries through the first 1/2 inch. Water them throroughly and allow the pot to drain completely.

Established plants require less water and can go for a long time between waterings. When you do water, make sure it's a thorough watering, then let the pot drain completely. Do not let them sit in water, which encourages root rot.

Temperature and Hmidity

Wax begonias like average to warm temperatures. As with all begonias, they do not like cold drafts and cannot tolerate freezing, but will thrive with temperatures in the 60s. While these plants thrive in humid outdoor conditions, indoor plants don't like especially high humidity, as it can encourage mildew on the leaves.

Soil

In the garden, wax begonias aren't terribly fussy about soil, provided it is well-draining. Dense soils can be improved by digging in peat moss or another organic amendment. As potted indoor plants, wax begonias prefer airy, light, fast-draining soil—a standard, general-purpose potting soil provides this.

Fertilizer

Garden plants should be fed monthly with a balanced granular or liquid fertlizer. With potted indoor plants, give them a feeding with liquid fertilizer weekly at quarter strength or biweekly at half strength. Every third or fourth feeding, use a high phosphorous fertilizer.

Are Wax Begonias Toxic?

Wax begonias are not included on any standard lists of plants toxic to humans. But they do contain calcium oxalates, which can cause mild to severe poisoning in animals. This toxin is especially concentrated in the roots.

Symptoms of Poisoning

The calcium oxalate found in wax begonias can cause vomiting, salivation, and, in large quantities, kidney failure in animals. Fatal consumption is rare, except occasionally with horses and other grazing animals.

Wax Begonia Varieties

Today, almost all plants known as wax begonias are hybrids produced from the same few ancestors. The basic ancestor is the B. cucullata, which was once called the B. semperflorens. This plant has been bred extensively over the years and its many descendants are correctly known as the Semperflorens cultorum group. The physical characteristics of these plants depend on the breeder, but they have been hybridized for various colors and heights. The B. schmidtiana species is also included in the semperflorens group. According to the American Begonia Society, this is a many-branched plant with small velvety leaves.

Some popular cultivars include:

  • ‘Super Olympia’: This is a variety that flowers early and is known for large, white, pink, or red blooms.
  • 'Varsity’: This cultivar is especially good for growing in pots. Its flowers are red, white, or pink.
  • ‘Paint Splash Pink’: This variety offers showy foliage, green with cream spots and marks. It has unique pale pink flowers.
  • 'Victory series': This group has bronze-colored leaves with large, showy flowers.
  • ''Cocktail series': These are dwarf varieties, 6 to 8 inches tall.

Potting and Repotting Wax Begonia

Grown indoors in pots, wax begonias will settle happily into being durable specimens that require little care. Many people move potted plants out to the patio or deck for the summer, bringing them back indoors once the weather cools in fall.

Use a general-purpose, peat-based potting mix to grow wax begonia, and use a pot that is smallish in size. Wax begonias like to be a bit root-bound, and they won't require much repotting—once or perhaps twice in their lifetimes, at most. In most cases, it's better to take cuttings of older plants than to struggle with repotting and rehabilitating leggy specimens.

If you are repotting, do it in the spring into a slightly larger pot with fresh, fast-draining, and richly organic potting soil.

Propagating Wax Begonia

Wax begonias are almost exclusively F1 hybrids produced by large nurseries in huge quantities. These plants will not produce accurately from seed, but like many other begonias, they propagate easily from leaf-tip cuttings. Take cuttings without blooms but at least two nodes and bury them in the moist potting soil mix, then leave in a warm, semi-shaded spot until new growth appears. The best time to take cuttings is in the spring.

Common Pests/ Diseases

Wax begonias—whether planted in the garden or as potted indoor plants—can be susceptible to powdery mildew, botrytis, and stem rot in humid conditions with poor air circulation.

Common insect pests include mealybugs and thrips, which can be treated with insecticidal soap.

closeup of a begonia flower
The Spruce / Kara Riley