Begonias are one of those flowers that everyone recognizes for their unique leaf shapes and lovely blooms. They’re frequently seen as houseplants, but growing begonias outdoors is a great way to give a shady area of your garden a bright spot of color.
Prized for their long-lasting coloring, begonias are even more valued for their lovely single and double blossoms, which are abundant when given the right conditions. Choose a variety with a lot of frill or more demure petals.
This tropical plant is found in South and Central America, Africa and parts of Asia, and were first named in the 1700s by French botanist Charles Plumier. The are many varieties of begonias, including cane, shrub, semperflorens and rex cultorum, but when most people think of begonias, they think of tuberous begonias.
You can find these plants in your local nursery, but you can also grow them by purchasing tubers that look like brown, dried mushroom caps. Growth comes from the concave side, so take care when you are planting them (see below).
Botanical Name: Begonia
Common Name: Begonia
Family: Begoniaceae
Plant Type: Annual
Hardiness Zones: 7 to 11 (USDA)
Sun Exposure: Partial shade, no full sun
Soil Type: Sandy, well-drained soil
Soil pH: 5.2 – 6.0
Maturity: 3-4 months from planting to bloom
Height: 6-18 inches
Spacing: 2-3 inches in containers
Bloom Time: Summer, fall
Flower Color: Orange, pink, red, white, yellow
Quick Guide: Planting, Growing & Caring for Begonias
- Gorgeous shade plant in vibrant colors
- Grows from tubers; should be planted in spring after all danger of frost is gone
- Tubers are not winter-hardy in colder climates
- Provide rich soil, regular water and protection from wind
- Pests and diseases include whitefly and various types of fungus
Begonia Plant Care
Begonias are a classic in the garden and for a good reason. This easy-to-grow plant can grow in a wide range of conditions and doesn’t need much to do well. You will be rewarded with beautiful flowers and foliage regardless of which of the many shapes, sizes, and colors you decide to go with.
There are plants that only produce single flowers with one row of petals, while others produce double flowers with two or more rows. But keep in mind that begonias, particularly the underground portion, are toxic to dogs, cats, and horses.
Wax begonias, the most well-known type, are named for the waxy appearance of their leaves. These hardy plants can be as short as six inches or as tall as nearly three feet, so they can fit in almost any space.
They can often grow in either full sun or partial shade. You can count on their brightly colored, either single or double, flowers all summer long. There are a variety of white-to-red tones within the wax family alone.
If you don’t mind a little extra work, tuberous begonias will give you stunning flowers year after year. They can grow upright or as a trailing plant. All you have to do is pull up the tubers in the fall, bring them inside for the winter, and replant them in the spring.
Colorful warm yellows, reds, oranges, whites, and pinks are just some of the options available with the Begonia boliviensis group of tuberous begonias.
With many different types of begonia plants out there, plant care instructions can differ slightly but here are all the main tips you’ll need to successfully care for your begonia plants.
Light
Most begonia varieties prefer partial shade and require bright light to flower well. Pick a spot with afternoon shade or morning sun to grow your begonias. Wax begonias can tolerate full sun as well, especially if their foliage is bronze. However, direct sunlight can cause leaf scorch in some begonia varieties, such as cane and tuberous begonias.
Soil
Since begonias are susceptible to root rot in overly wet soil, look for spots with well-drained soil. Since they are native to cliff walls, Begonia boliviensis varieties in particular prefer good drainage. For better drainage, amend heavy soil with compost or sand.
Water
Begonias require a delicate balance when it comes to watering in order to thrive. They are drought-tolerant to a point, but for best results, they need to be watered regularly.
Most types need to be watered regularly, but they shouldn’t get too wet because that can cause root rot and kill them. Don’t be afraid to allow your plants, including those in container gardens, to dry out slightly between waterings.
The best time to water these annuals is in the early morning. Watering during periods of intense sunlight should be avoided because it can cause leaf scorch. Watering at the base of your begonias with a soaker hose can help reduce the risk of fungal disease problems.
Temperature and Humidity
Most varieties thrive in warm, humid conditions. The most common variety, wax begonias, are delicate in the cold, so it’s crucial to plant them after the last frost.
Tuberous begonias must be dug up annually and replanted in the spring because they cannot survive the winter. These types of begonias don’t do well in hot, humid conditions like wax begonias do. Instead, they do best in cooler temperatures. In a similar vein, rhizomatous begonias florish in milder conditions.
Fertilizer
Begonias aren’t heavy feeders but they can do well with a regular dose of fertilizer formulated for annual flowers that’s ideally well-diluted, to support the flurry of blooms they will unavoidably produce. Look for one with an equal mix of nitrogen, phosphorus, and potassium, and mix it into the soil when you first plant your begonias.
Once the first flowers appear, you should switch to a fertilizer that is higher in phosphorous than nitrogen and continue to apply it once a month if you want to encourage an abundance of flowers.
If healthy plant growth and goof foliage is your goal, an balanced fertilizer will work well. Begonias are easily scorched, but a slow-release fertilizer formula can help. This is a common problem with Rex begonias in particular.
Apply a diluted high-nitrogen fertilizer to tuberous begonias every two weeks, beginning with the first flowering and continuing until the end of May. Next, switch to a low-nitrogen or balanced formula.
Stop fertilizing tuberous plants around the end of August. This will make them go dormant so you can dig them up and store them for the winter.
Pruning
Begonias clean themselves, so you don’t have to remove or deadhead their old blooms during the growing season. In any case, plants can benefit from periodic pruning, especially if they start to get leggy.
To prune the plant, just pinch back the stems until you reach the first or second healthy bud. New development will spurt out from this juncture, bringing with it a flurry of blossoms and leaves.
Overwintering
In colder climates, tubers will not survive the winter, so you need to dig them up to preserve them.
Toward the end of the growing season, watch plants carefully. When the lower leaves begin to turn yellow, stop regular watering and let the plant die back a bit. Dig up the entire plant, then set it on newspaper, a rack or a crate to completely dry out for a few weeks.
Next, clean off any remaining plant material or soil from the tubers, discard any tubers that look damaged and pack the healthy ones away in a box between layers of newspaper. Do not use plastic, which encourages mildew. Store them at a cool temperature that stays above freezing. 40-45º F is ideal.
In the spring, you can take them out of storage 8 weeks before the last frost to start them indoors or wait until after the last frost to plant outside.
Common Types of Begonia Plants
Wax Begonia
The most common types are those of the Begonia semperflorens species, which are also known as wax, annual, or bedding begonias. They are grown primarily as annuals, reaching heights and widths of 6 to 12 inches.
Planting these shade-tolerant flowers under trees or tucking them into planters, hanging baskets, or window boxes will result in voluminous displays of vibrant color. Wax begonias
Tuberous Begonia
Another common variety, tuberous begonias, are stunningly colorful and look especially breathtaking in hanging baskets and other containers.
In addition, they have a larger growth habit than wax begonias, reaching heights of 12 to 18 inches indoors and 3 feet or more in outdoor containers.
Cane Begonia
Cane types have beautiful foliage and bloom in a variety of colors. They have an upright growth habit and segmented stems.
This group also includes angel wing begonias, so named for their wing-shape leaves. They are well-liked and suitable as indoor plants, but they can also be grown outdoors.
Their size varies according to growing conditions, ranging from 6- to 12-inch houseplants to 5-foot shrubs.
Rhizamatous Begonia
Rhizomatous begonias, the largest class, are distinguished by their relatively thick stems, or rhizomes, which spread new roots and leaves close to the soil surface.
They are commonly grown as houseplants due to the uniqueness of their leaves and stems. Plants range in size from a few inches to three feet tall and wide.
Rex Begonia
Rex begonias (Begonia rex) are a type of rhizomatous begonia that typically grow to a height and width of 12 to 18 inches and are readily available all year long at florists and garden centers.
They are popular houseplants because of their unique leaves, but they can be hard to take care of. And when paired with ferns and other plants that thrive in part shade, they make for a beautiful summertime addition to any flower bed or container.
They are grown for their leaves, which come in many different hues.
How to Plant and Grow Begonia
Site Preparation
Choose a shady, protected spot that won’t get too dry. A place with morning sun and light breeze is ideal, since begonias will scorch if they have too much sun or wind.
Whether you’re planting in containers or an outdoor site, choose well-draining soil that’s on the acidic side. Supplement with compost and peat moss if your soil is poor or heavy, or use a container mix that has a high peat moss content.
Like all tropical plants, begonias need warm temperatures, so only plant outdoors once all danger of frost has passed but before hot weather hits. You can start tubers indoors 8 weeks before transplanting so blooms will appear sooner.
Keep soil moist, but overwatering can damage the tuber and encourage mildew.
How to Plant Begonia
For containers, get tubers started by filling a pot or window box with a quality mix, then dig holes about 2 inches deep and 2-4 inches apart. Place tubers hollow side up, cover with soil and water. Make sure not to overwater or tubers will rot.
When planting outside, make sure all danger of frost has passed. Dig holes about 8 inches apart (this tool makes it easy) and 2-3 inches deep. Do not plant too deeply. Make sure to plant the tubers with the hollow side up. Cover with soil, water lightly, and wait to see new growth until you begin watering regularly.
Once the plants start blooming, pinch off fading flowers to encourage branching and new growth.
Common Pests and Plant Diseases for Begonia Plants
Begonias generally have few issues with pests. Mealybugs, spider mites, thrips, scale, slugs, and snails are some of the pests that may make a home in them.
However, the most common pest is whitefly, which can be treated with natural pesticides or insect predators like ladybugs or whitefly parasites.
When it comes to fungal diseases, keep an eye out for powdery mildew, which appears as white dust on the leaves. Grow your begonias in an area with lots of air circulation and avoid overwatering your plants because excessive moisture can increase the likelihood of disease.
In moist environments, begonias are more susceptible to Botrytis blight (gray mold), which causes a gray, fuzzy layer to appear on the flowers. When you water a plant that has this fungus, keep the leaves dry because it can spread through splashing.
Begonias may be affected by Pythium root and stem rot, which is caused by a fungus-like organism. The stems closest to the soil in mature plants may become darker in color and waterlogged, eventually collapsing.
This is also associated with overwatering. When too much moisture causes root rot, which begonias are especially prone to, it’s often too late to save the plant.
You may also see powdery mildew, leaf spot, and root, stem and leaf rot. Many types of mildew, leaf spots and blight can be remedied using a liquid copper spray.
In general, pests and diseases seem to attack begonias when they are being overwatered, so head off potential problems by watering when soil is dry and providing adequate circulation.
Eric is now retired, but is still a renowned gardener known for his expertise in composting, organic gardening and pest control, utilizing pesticide-free options, such as beneficial insects.
Eric believes when you do something good for the environment, the effects will benefit generations to come.
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