The Tuberous Variety of Begonia-Big, Beautiful, Blooms

February 21, 2020

There are over 1000 varieties of Begonias. The tuberous varieties are among the most spectacular of them all. We value these especially the large flowers. The blooms come in every color but blue or purple. Some are Picotee, meaning that the body of the flower is one color and the petal is edged in a contrasting color. The shapes are varied; plain, single, double, ruffled, or toothed. The flowers can be as large as 8″ in diameter.

They come in a cascading form, good for hanging baskets and an upright type about 1′ tall. They may be well worth the effort. Are they difficult to grow? People who do well with them say if you follow the basic rules you will succeed. They need morning sun, fertile soil and excellent drainage. They are not always long-lasting; in too much heat and humidity they will die off. However, the tubers can be replanted another year.

Where Do They Come From-How Did They Get To Us

Thank Charles Plumier

Begonias were documented in Brazil in 1690 by Charles Plumier, a French, Franciscan Monk, who was a mathematician, a botanist, a bold plant hunter, and a draftsman. (The Frangipani genus Plumeria is named for him.) In his plant hunting career, he documented over 4000 plants and 1000 animals from the Caribbean and Central America.

We celebrate his accomplishments because he documented so many species and made them accessible to the world’s gardeners. However, his Brazilian source may not be the oldest. They were used in Mexico and very early in China where they had food and medical uses.

How to Use The Plants

These lush flowers are popular as bedding plants, container plants and in hanging baskets. (Use the Cascading form for this.) Plant in bright shade, in rich, well-drained soil.

If your garden has deep shady areas, you may want to create some contrast and brighten those areas. Begonias, with their variety of color, size and shape are perfect for that purpose. Try them.

In What Planting Zones Are Tuberous Begonias Hardy

There is a variety of opinion here. Some sources say that they are hardy in zones 8-11. For some gardeners, this may be correct. Here is a link to a more conservative gardener’s position. Even in a climate warm enough to leave the tubers in the ground, the tubers will rot if they are sufficiently wet. Use your own judgment.

They will be useful in zones as cold as zone 3 if used as summer annuals or if the tubers are brought inside. Do you want to grow them in Florida? Here is some information from U. FL.

How to Plant the Tubers

Select a protected spot for your plants. Morning sun with dappled shade for the rest of the day is ideal. They will require protection from wind.

Plant the round tubers hollow side up in a well-drained potting mix. Place them 1″- 2″deep and 8″ apart. Keep them in bright indirect light, indoors at over 60. A heating pad can speed up the process. After about 3 weeks the surface will begin to crack. When they have filled the small pot, transfer them carefully to a pot with a diameter of 7″-10″.Before buds appear, feed with 5-1-1 fertilizer such as fish emulsion. When the plant fills the pot and all danger of frost has passed you can place them outside in a well-ventilated location with bright shade.

When To Start The Tubers

The time from tuber to flower is 10-12 weeks. The suggested time to start them in pots, indoors is 8-10 weeks before the date of the average last frost in your area. How do I estimate that date? Here is a link to the NOAA site, It should help you.

How to “Harden Off” The Plants For The Garden

Accustom the plants to” life” in the garden. Put your garden ready potted plants outside in a sheltered location. Leave them for one week, bringing them in at night if the weather is unfavorable.

Fertilizer and Water

You may have noticed that heavy blooming plants tend to equal heavy feeding plants. Feed, in gentle applications after buds form with 0-10-10 fertilizer. Repeat this every two weeks during the blooming season. When the plants start to decline in late summer or early fall, discontinue the fertilizer. Signs of decline include the ending of blossom formation and yellowing leaves.

Water the plants when the soil begins to be slightly dry. Do not permit soggy conditions as tubers can rot.

Pests and Diseases

Pests

These include some of the usual suspects, aphids and thrips. They cause damage and disease as they feed. Remove any weeds and damaged leaves. Use water to wash them off and insecticidal sprays. More information

Diseases

Powdery Mildew-this is identified by white spots on both sides of the foliage. This occurs in crowded or shady areas. Space the plants 12″ apart to prevent crowding. Advice from U.Mass

Root and Stem Rot-is caused by soil fungi. Ensure that you have well-drained soil.

Here is some IPM advice from U. CA

When Winter Comes-How to Overwinter the Tubers

Within a few days of the first killing frost, carefully dig up the tubers. Some gardeners say that this should be done before a freeze. Leave a small bit of soil attached. Cut the stem 1″ in length and cure in a cool dry place for 2-3 weeks. Store them for the winter at 40-50, packed in peat moss, vermiculite, or sawdust. Do not permit them to freeze.

Can I Use Tuberous Begonias As A House Plant Over The Winter?

Sorry, probably not. They have much higher requirements for light and humidity than other Begonias. If you still like the look try the fibrous or rhizomatous varieties. If you choose to overwinter the tubers you can enjoy them again.