Begonia grandis is a favorite of people who want vibrant color in their gardens but have shady yards where full sun perennials and annuals won’t bloom. Not to be confused with the popular houseplant, rex begonia, these low-maintenance herbaceous flowers will thrive in shade or partial shade, providing charming pink and white small blooms from mid-summer through the first frost in fall.
I. Appearance and Characteristics
Begonia grandis, the hardy begonia, is a species of flowering plant in the family Begoniaceae. This herbaceous perennial has alternate, simple leaves on arching stems. The flowers are pink or white, borne in dichotomously branching cymes from late summer through fall in USDA U.S. Hardiness Zone 7. As the common name “hardy begonia” implies, it is winter hardy in some temperate regions.
It can overwinter well in hardiness zone 9a in southwestern Japan as tuberous roots or bulbils (bulbils are formed in axils). Above-ground parts of this plant eventually die as temperature lowers. However, it is generally regarded as hardy to zones 6–7.
The varietIes Begonia grandis subsp. evansiana and Begonia grandis subsp. evansiana var. alba have gained the Royal Horticultural Society’s Award of Garden Merit.
II. How to Grow and Care
Sunlight
Begonia grandis is a perennial flower that blooms best in partial shade or shade. They should never be planted in direct sunlight, though they can tolerate dappled, indirect light, particularly in the morning or late afternoon.
Temperature and Humidity
Begonia grandis begins blooming in the middle of summer and continues through the first frost, but it doesn’t immediately die off as the temperatures drop. It is hardy down to Zone 6 and tolerates summer heat up to Zone 9. Despite its tropical look, it is not a hot water-loving tropical plant.
Once temperatures hit much below freezing, the foliage will begin to die back until the next winter.
Watering
Hardy begonia prefers humid environments, so it should be watered regularly to keep the culture media moist. In high temperatures, if not watered sufficiently, the stems of the plant are liable to fall and the leaves are apt to wither. For outdoor or pot planting, as long as it is in the plant’s growth season, water the plant when the soil feels dry to the touch, water the soil until it is totally wet, and then drain excess water. Note that the watering amount should not be too much, as water accumulated in the pot can cause root rot.
The varieties of begonias with ornamental leaves are in vigorous growth in summer. Besides regular watering, it needs to be sprayed several times a day to keep the relative humidity at 56%-60%. In winter, hardy begonia grows slowly, and the amount of watering can be reduced accordingly. It can be watered once every 3-4 weeks until it grows again in spring.
Soil
Hardy begonia grows well in a well-drained mixture of sandy soil, clay and loam, with a suitable pH range of 5.5-6.2. However, hardy begonia will grow better in soilless environments than in conventional soil. Planters can buy ready-made soilless culture media, or mix 2/3 peat moss or peat with 1/3 other soilless culture media such as vermiculite, bark and perlite to provide a slightly acidic and well-drained media for the plant.
Fertilizing
To increase nutrition, hardy begonia prefers properly diluted fertilizers or fertilizers mixed with a little compost and peat moss. After flowering, it is necessary to start applying fertilizer regularly, but not too frequently. Adding liquid fertilizer about once a month is the recommended frequency, and you can choose to buy different kinds of fertilizer according to the needs. Hardy begonia is sensitive to excessive fertilizer, and high concentrations of fertilizer can damage the leaves. Fertilizer should not be applied frequently in late fall and winter because it does not grow steadily during this period, even in dormancy.
Planting Instructions
Sowing is recommended to be done after frost in winter because hardy begonia grows best in warm environments and a gradually warming climate allows it to thrive. Hardy begonia seeds are small, and need to be evenly mixed with fine clean sand and sprinkled on the media when sowing. During its growing process, patient waiting is needed, and exposure to direct light should be avoided. Usually, it will sprout when midsummer comes.
Pruning
When the flowers begin to turn brown and die after blooming, withered flowers and leaves should be pruned right away to promote new growth. Removal of withered flowers and leaves will prevent them from falling into dense bushes and rotting later, thus causing disease. At the end of the flowering season, it is necessary to remove the branches and buds with poor growth such as yellowing, dryness and thinness. After flowering, tuberous begonias will store all the nutrients in the bulb for the next growing season. plants can be pruned in cool and mild fall. When pruning, it’s better to remove the apical buds in the long lateral branches and remove the first one or two healthy shoots to promote more branches.
Propagation
Hardy begonia is usually propagated by cutting. Stem cutting can be carried out at room temperature all year round, but it has the best effect in late spring and early summer, with fast rooting speed and high survival rate. The tops of plump stems are often used as scions. It is better not to use flower buds as scions.
Leaf cuttings work best in spring and fall. It can also be carried out at room temperature or in winter, but rooting speed is relatively slow. The cuttings should be fully developed mature leaves. Leaves that are too tender or aging heal and root slowly and the probability of forming mature seedlings is low.
Cuttings should be placed in well-drained containers, and a mixture of vermiculite, peat and perlite can be used as the culture media. Keep it in a bright and warm place, away from direct sunlight and ensure that the soil contains a small amount of water to keep it moist.
Pests and Diseases
Common Pests and Plant Diseases
Begonia grandis is generally a low maintenance, easy to care for plant, but there are a few pests and diseases to watch out for. They can be a target for bugs like mites, mealybugs, thrips, whiteflies, and nematodes. They can suffer from root rot if conditions are too moist or powdery mildew.
Common Problems
There are cases where your begonia grandis may not flower as expected. In those situations, it’s most likely because the soil either isn’t rich enough or there is too much shade. Too much water can cause the leaves to turn yellow.
Overwintering
During cold winters, potted hardy begonia should be transferred indoors or in greenhouses for maintenance. For open-field plants, appropriate warming measures should be provided, such as covering with 5 cm of peat moss, tree leaves, sawdust or straw, or covering plants with fabrics or cardboard boxes. Do not let coverings oppress plants.
Mulching
During cold winters, potted hardy begonia should be transferred indoors or in greenhouses for maintenance. For open-field plants, appropriate warming measures should be provided, such as covering with 5 cm of peat moss, tree leaves, sawdust or straw, or covering plants with fabrics or cardboard boxes. Do not let coverings oppress plants.
III. Uses and Benefits
Hardy begonia is a hardy deciduous perennial commonly found in shade gardens. It is prized for its lush red-veined foliage and pretty summer-time blooms. Its clump-forming habit makes it suitable for mass planting and borders. Hardy begonia is a great choice for cottage and pollinator gardens. Suggested companion plants include hakone grass or plantain lily for color contrast.
IV. Harvesting and Storage
Hardy begonia doesn’t have long straight stems, so it is not usually used as cut flowers. According to personal preference, the top flowers can be collected for flower specimen pressing or other purposes. They can be collected at will as long as it is growing season, but don’t take away too many stems and leaves.