August 2009
Home Grown Tomatoes

Begonias 101


Male and female begonia flowers. 

As I promised last month, we will take a closer look at begonias and I will try to help you understand why these beauties are favorites of mine.

Begonias are flowering plants that grow in sub-tropical to tropical moist environments, typically between 15° north and 15° south of the Equator. There are more than 1,300 species of the genus Begonia.

The begonia societies recognize seven basic categories:

Baby begonias.


Cane-stemmed: Begonias with long stems with swollen nodes, much like bamboo. They are grown for their foliage as well as their cascading clusters of flowers. Plant these in a rich, heavy mix to support the height of the stalks. Fertilize with Jack’s Classic® 20·20·20 twice as often at half the rate as recommended on the label during the spring and summer. Back off to one-forth as often in the winter.

Tuberous: Tuberous begonias, or hardy begonias, are fairly easily identified by their swollen bulb at the base of the plant. Some tuberous varieties are somewhat hardy, even in Central Alabama. These begonias like a slightly acidy soil that quickly drains. They are likely to contract root rot if the soil is too heavy. These should be planted in dappled sunlight to shade and fertilized with a fish emulsion 5·1·1 or vermi-fertilizer 1.5·.5·.5 during the growing season and increase the P and K to 0·10·5 during bloom cycles. Some of these begonias have a dormant period. The tubers, or bulbs, should be removed from their growing beds and stored in a cool, dark container of dry, milled peat moss during dormancy, much like one would treat caladium bulbs.

Rex-cultorum: Though these begonias generally grow from a rhizome, they are not classed with other rhizomatous species. Rex begonias are prized for their foliage and mostly cultivated as houseplants, patio container plants or accent hanging basket plants. Their blooms are not nearly as showy as their bold-colored and shaped leaves. A good fertilizer to use is 19·6·12 Osmocote® 3-4 month control release.

Rhizomatous: Rhizomatous begonias grow from a modified stem or rhizome. Leaves come up from a central rhizome to form a mound or ball of foliage. The rhizome stores food and water thereby making this type of begonia a little more resilient than other types. Use a well-draining potting medium in a shallow clay container. Don’t over-pot. If you remove your begonia from a 4-inch bulb pan, then pot it in a container no bigger than five-inches in diameter. Use Jack’s Classic® 20·20·20 fertilizer during the spring and summer, but don’t fertilize during the fall and winter.

Winter-flowering: These are usually fibrous-rooted, bushy, compact plants that bloom during cooler temperatures, 59-68°F. Winter-flowering begonias like bright, filtered light, relatively low humidity and good ventilation. Use a complete fertilizer on these begonias.

Shrub-like: Shrub-like begonias are usually grown for their leaf patterns and colors, but the blooms can be quite showy as well.  They are mostly bushy with erect or semi-erect stems that sometimes grow horizontally as they mature due to the weight of the branches. Shade from direct sun during hot months.

Semperflorens: Semperflorens, wax, annual begonia: All these names apply to this group. These begonias are most often found in the springtime in flats as bedding plants. Semperflorens begonias tolerate more direct sunlight than other types. Plant in well-drained soil. Do not over-water. During the growing season, I recommend a control release fertilizer supplemented by a balanced liquid feed. When the growing season is done, be sure to pot some in clay containers and bring them in to enjoy for the winter.

Do you want to know more about begonias? For propagation techniques and other growing information, logon to the newly redesigned Home Grown Tomatoes website at

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