Flowering annuals: Year of the begonia

“Extension on the Go” podcast by Debbie Johnson. Episode 157: The Year of the Begonia

COLUMBIA, Mo. – Once considered a denizen of the shade, begonias today are versatile garden plants that can be used in a variety of ways. This year, the begonia has its moment in the sun as the National Garden Bureau’s flowering annual for 2016.

“Some begonias are grown for their uniquely shaped leaves; others are prized for their flower. Many work well as container plants, and if you’re looking for pretty edger for a formal bed or border, begonia is a great choice,” said David Trinklein, horticulture specialist for University of Missouri Extension.

Begonia is a very large plant genus that contains more than 1,700 species. Most belong to one of two broad categories based on their root structure.

Fibrous-rooted begonias

These are also called “wax-leaf begonias” because the leaves are shiny as if they’ve been oiled. They can also tolerate a variety of exposures.

“They will put up with shade or full sun, but need highly organic soil that retains water when grown in sunny areas. Additionally, they must receive adequate water,” Trinklein said.

Wax begonias produce a multitude of small flowers and come in shades of red, pink and white. They also are available in two leaf colors, green and bronze. In full sun the bronze-leafed types often turn an attractive reddish-orange.

Trinklein says they are perfect for edging in formal flower beds or along a formal border.

“Fibrous-rooted begonias are what I call a very prim and proper plant,” he said. “They’re very neat, very slow to enlarge and never get out of bounds.”  

Tuberous-rooted begonias

These shade-loving plants can thrive in very little direct sun.

“Which is good news because there are very few plants that will give us good color from flowers when there’s a limited amount of sun,” Trinklein said.

Tuberous-rooted begonias make great bedding or border plants as long as the sun exposure isn’t too severe, he said. They also work well in container gardens located in a shady setting.

As with the fibrous-rooted begonias, they need a highly organic soil, or amended garden loam, and sufficient water.

“Begonias of all types have very fine feeder roots,” Trinklein said. “The root system can’t reach down into the soil profile for water, so you must keep them watered. Not soaking wet, but moist.” 

Germination

While most tuberous-rooted begonias are vegetatively propagated, fibrous-rooted begonias are grown from seeds. This can be a challenge for the average gardener because the seeds are very small, almost dustlike in appearance, Trinklein said.

“A very fine-textured and porous germination medium is required to successfully start begonia seeds,” he said. “If you try to start them a coarser medium, the tiny seeds will drop into cracks and crevices and might not be able to emerge before depleting food reserves.”

Even when placed in a proper growing medium they grow very slowly. When the seedlings first emerge, they’re barely big enough to see.

“It may be eight weeks or more before they’re large enough to be transplanted into a bedding plant container,” Trinklein said. “Then it will take more time before the plant is large enough to be transplanted into the garden.”

Because the fibrous-rooted begonias are such a challenge to grow from seed, Trinklein recommends that home gardeners buy these begonias as started plants.

So, if you’re looking for ways to add color to shady areas or need attractive border or edging plants, take another look at begonias.

For more information, the MU Extension publication “Flowering Annuals: Characteristics and Culture” (G6629) is available for download at http://extension.missouri.edu/p/G6629.