An article by: John J. Marshall
For bold, eye-popping hues in container gardens and color beds, go with tuberous begonias. Tuberous begonias are perennials that grow from swollen stems. Roots emerge from the bottom; shoots and leaves appear along the top and sides. Their parentage can be traced to species found in South America and hybridized during the late 19th century.
Their botanical name is Begonia x tuberhybrida. The genus is named for Michel Begon (1638-1710), naturalist and governor of New France (French Canada). Tuberhybrida means “hybrid tuber.” No surprise there, eh?
Tuberous begonias produce beautiful, succulent foliage, typical of the genus. Impressive flowers appear from mid-summer until cold weather stops them. Colors are available throughout the color spectrum. Common flower forms include double or camellia-types, fimbriata or carnation-types, and pendulous. Their appearance is very lush. Plant height is around 12″. They lend themselves to all kinds of uses from container gardening in small spaces to mass plantings in flower beds. They’re wonderful for hanging baskets, especially the pendulous forms.
Tuberous begonias can be grown almost anywhere in the United States, but they are reliably hardy only in USDA climate zones 10 and 11. Some gardeners lift and store over winter in cooler zones, but they are rather inexpensive so are often treated as annuals.
Begonias prefer partial to full shade. Rich soil, moist but well-drained, is best with mildly acidic pH ranging from 6.1 to 7.5. The best way to determine if the pH is within range and contains the proper nutrients is to have the soil tested. Your local Cooperative Agricultural Extension Service can help you. You can collect the soil sample yourself. For a nominal fee, they will send your soil sample to a laboratory for analysis. Be sure to call the Extension office for instructions.
If you use potting soil, choose the finest grade available. Cheap soil will give poor results. The best potting soils will be light-weight, peat-based with added materials to enhance plant growth. Select containers that will allow you to include companion plants, if desired. Larger containers will require less frequent watering. The addition of water retentive gel can be beneficial.
Cultivate the soil, if necessary, and remove weeds. If you use synthetic fertilizer, allow at least a week before planting so it can be incorporated into the soil by rain or irrigation and not burn the tubers. Time-release fertilizers for annual plants are excellent.
Plant your begonias in spring after the danger of frost has passed. Planting holes or trenchs should be about 3″ deep. Space the rhizomes about 8 to 12 inches apart. Lay them flat in the bottom of the hole or trench. Don’t worry about which side is up. Cover with about two inches of soil. Water deeply. If some of the soil washes away, add more.
During summer, you may fertilize occasionally. Irrigate if rainfall is inadequate. Keep soil moist, but not soggy.
When I plant color, I tend to go “hog-wild.” No dabs here and there for me. I like lots of it. I think you will, too. Try a box of tuberous begonias in your garden. You’ll be surprised how many ways you can use them.