Vivid blooms, dramatic foliage – begonias are your solution for summer flare. Tuberous begonias can be found in colors from deep scarlet to pure white, and picotee types offer contrasting colors such as bright yellow with orange edges, or white with pink tinge. They are great performers in containers, borders or planted in a raised bed blooming June to October.
If you want all the benefits of this edgy bloomer, you must plant tubers now! Sold as tubers in spring, begonias must be planted now as they can take up to 3 months from planting to full bloom. Start indoors at least a month before expected last frost date (May 10th for our Willamette Valley region). Set tubers 1 inch apart, hollow side up, in shallow pots filled with moistened potting soil. Cover each tuber with about an inch of potting soil, watering thoroughly at planting to stimulate growth, and maintain moist soil conditions as to never let the soil dry out completely.
Once sprouted, 1 to 2 inches tall, re-pot tubers into 6 inch tall pots or where you’ll want to enjoy them for the blooming season ahead. Cover the tubers with 2 inches of soil, and no more. After danger of frost, move containers to a partly shaded outdoor location where they’ll receive either early-morning or late-afternoon sun.
If planting in beds, set begonias 8 to 12 inches apart. Fertilize regularly for consistent blooms all summer long. Avoid getting the foliage of the begonia wet as too wet of conditions can lead to powdery mildew. Deadhead plants regularly to reduce disease pressure.
Tuberous begonias are only hardy to zones 9 and 10. Before frost comes in the fall, you can remove tubers from containers and set them in an airy and shady place indoors to dry. After tops have dried, remove them and store tubers in dry peat moss in a cool, dark place such as your garage, where temperatures will stay between 35 and 45 degrees. In late spring, begin the cycle again!