Starting tuberous begonias indoors can help shake winter doldrums

Published Jan 28, 2018 at 9:00am

Despite the gloomy weather, it’s the perfect time for starting tuberous begonias indoors to get them ready for your outdoor garden.

Begonias belong to a huge plant family, the Begoniaceae, with over 1,000 species.

Tuberous begonias are a unique variety, which are grown from underground roots called tubers.

The plants range from short upright varieties to the flowing hanging basket types. Their flowers are unmistakable and very showy; the color range is amazing and many will bloom non-stop all season long.  

Planting

Tubers are available, either through mail order, on-line sources, local nurseries or retail outlets. You want to start the tubers about 8 weeks before the average last spring frost date.

Use a pot with drainage holes; be sure you have a good quality potting soil to give the plants a good start. When planting the tubers, place the indented side upward; the rounded side is the bottom. Cover the tubers with 1/2 to 1 inch of potting soil and water well. Tubers will rot easily, so keep the soil moist but not wet.  

Temperature, Light
and Fertilizer

Place containers in a warm location, around 70 degrees. You will have more success by placing the pots on a heating mat, especially if your home is on the cool side. Heating mats are inexpensive and easy to find; normally used to keep seed trays warm. Once the tubers start sprouting, move the plants to a sunny window or place them under fluorescent lights. Fertilize with a diluted liquid fertilizer once every two weeks.

You can bring your pots outdoors or transplant them into the ground once all danger of frost has past. However, before you bring them outside, they have to be “hardened off”.

This process takes about 7 to 10 days and involves getting them used to the transition from indoors to outdoors. Start by placing the plants in a shady, protected location for a few hours each day before permanently exposing the plants to their permanent outdoor location.

Outdoors, these plants perform best in well-drained soil in a location with morning sun and afternoon shade. The plants can be a challenge to grow if placed in full sun. If you transplant into the ground, be sure to plant them at the same depth they were in the container.

Keep them evenly moist throughout the growing season and deadhead spent flowers. Be on the lookout for slugs and snails and use appropriate slug baits to keep them away. In the fall, you can move potted plants back indoors for winter or dig up the tubers and store them for next year.

The colors available along with different bloom forms and sizes make this plant a superstar for the part-shade or shade garden. Many varieties can be quite expensive to buy as plants.

Start looking at the many catalog and on-line sources and save money by starting your own.

You will not be disappointed! Visit Cornell’s gardening website at gardening.cornell.edu. Once on the site, click on “Garden Guidance, Lawns & Landscapes” to see various annual and perennial flower fact sheets including one on tuberous begonias.