Tuberous begonias live up to their name. From the thick rhizomes, leaves sprout in the spring, forming a dense bush.
The flowering period for tuberous begonias begins quite early. In a suitable location and with the right care, these perennial bloomers will delight you until autumn.
The genus Begonia within the Begoniaceae family includes about 1,400 species worldwide, native to tropical and subtropical regions of Africa, Asia, and South and Central America.
Tuberous begonias (Begonia x tuberhybrida) are cultivated forms of various species of this genus, originating from the Andes of Ecuador, Peru, and Bolivia.
The cultivars designated as Begonia x tuberhybrida are offered as hanging begonias (Begonia pendula) or scented begonias (Begonia odorata).
Tuberous begonias grow perennially. They are herbaceous plants that develop an underground rhizome as a survival organ.
Their growth height ranges from 8 to 16 inches (20 to 40 cm). There are species whose shoots grow in a flat creeping, hanging, or emergent manner.
The foliage of tuberous begonias is asymmetrically shaped. The leaf blade is heart-shaped at the base and is extended to the tip. It has a coarsely serrated or toothed leaf margin and a raised midrib from which numerous lateral veins branch off.
The laterally departing veins branch into smaller leaf veins, each of which ends in a tooth of the leaf margin. The leaves are dark green in color, coarse leathery, and fleshy thickened. But there are also varieties with reddish-colored foliage.
Tuberous begonias are monofloral. Both male and female flowers reside on one plant.
Newer cultivars bear densely double male flowers. These are not reproductive, unlike the semi-double female flowers, which have stigmas visible in the center.
The ratio of male to female flowers varies throughout the year depending on the weather. As a result, there are times when plants bear different numbers of double and semi-double flowers.
The flowers of wild species show these petal properties:
- Identically shaped petals
- Male flowers with two to four petals
- Female flowers with two to five petals
When is Flowering Time for Tuberous Begonias?
These herbaceous ornamentals prove to be perennial bloomers, with blooms beginning in May and lasting through October.
Some varieties even bloom until the first frosts. Tuberous begonias shine in white, yellow, orange, pink, or red.
Tuberous begonias often grow as annuals. They decorate window boxes on balconies with a northern exposure.
Pre-grown plants start flowering early, so they are perfect for starting the season on the balcony. Varieties with hanging shoots are a perfect choice for planting hanging baskets. They can decorate interiors, terraces, or house entrances.
Their rhizomes allow perennial cultivation, though. This makes the plants attractive for the design of flower beds.
Due to their site requirements, tuberous begonias are suitable for underplanting shrubs and trees. With their flowering splendor, they decorate pot arrangements on roof terraces very well. You can even use them for indoor greenery or cultivate them in the winter garden.
Which Location is Suitable for Tuberous Begonias?
Begonia hybrids thrive in partial shade and shady locations. Sunlight hours in the morning or evening do not bother the plants, though.
They do not tolerate the blazing midday sun, as the leaves quickly dry out in the heat of the sun. You should also protect the growing site from wind and rain, as shoots and flowers will quickly break off or damage.
What Soil Do Tuberous Begonias Need?
The soil should be rich in nutrients and ensure a loose structure so that water can drain easily.
To improve permeability, you can mix some sand into the substrate. Normal potting soil is suitable as a planting substrate.
Propagating Tuberous Begonias
The easiest method of propagation is by division, which is possible in spring shortly after fresh sprouting.
Dig up the begonia and divide the tuber into about eight divisions. Make sure that each tuber piece has an eye so that it can sprout.
You can clean the rhizome with a soft brush to make the eyes more visible. If the root has not developed sprouting eyes, you should store it in a warm place.
As soon as it begins to bud, you can cut the sections accordingly. Then, place the parts individually in pots with permeable substrate and water them.
You should pay attention to the following points:
- Thoroughly clean the knife before cutting.
- Allow tuber pieces to dry out after cutting.
- Dust the cuts with charcoal.
- Pour away excess water from the saucer.
You can prepare tuberous begonias indoors starting in February so that they start the flowering season early.
The rhizomes will germinate when temperatures no longer drop below 50 °F (10 °C). Store them in lukewarm water for 24 hours before planting so that they swell slightly.
Cover the bottom of a planter with shards of clay, pebbles, or expanded clay to prevent water from accumulating. Fill the pot three-quarters with the substrate.
Place the rhizome on top of the soil so that the root side is facing up with the depression clearly visible. The tubers should only be halfway inside the substrate. Moisten the substrate slightly.
Place the pot in a place with temperatures between 50 and 59 °F (10 and 15 °C). Ideally suited is a location in an unheated winter garden or basement.
The thermometer should not rise higher than this, as the fresh shoots will develop soft and unstable in locations that are too warm.
As soon as the plant has grown about 1-2 inches (2-4 cm) high and forms the first leaves, you can move the planter to a brighter and warmer place.
Care and Further Culture
Do not leave the tuber in the wet substrate. Spray the substrate with water twice a week, making sure that the rhizome does not catch any water drops.
A transparent cover will prevent it from drying out. You should remove this daily to prevent mold growth, though.
During rooting, the tuber hardly needs water. The need increases as soon as the first leaves are visible.
At the end of April, the acclimation period begins. Place the planter outside in a shady spot for several hours each day. Temperatures should be at least 59 °F (15 °C).
In this way, the tuberous begonia can gradually harden off and adapt to natural weather conditions. In the evening, bring the plant inside as a precaution, so that late frosts can cause no damage to it.
Propagation by seeds requires patience and tact. Scatter seeds on a growing medium between December and January and moisten them lightly. For the seeds to germinate, they require temperatures between 73 and 79 °F (23 and 26 °C) and high humidity.
Tuberous begonias are light germinators. Therefore, seed propagation works best under growing lamps. Put glass covers over the planters, so that the heat does not dry out the substrate.
Under optimal conditions, the seeds germinate after two to three weeks. The success rate is not particularly high, though.
As soon as the first shoots are visible, reduce the temperature to about 59 °F (20 °C) and also reduce humidity.
Strong sunlight will damage the tender shoots and leaves of the young plants.
Up to seven weeks pass before the plants can be pricked out. Only then is cultivation possible at about 59 °F (15 °C).
Cut a few leaves from a vigorous plant and put them in a filled planter. A mixture of potting soil and sand is suitable as a substrate.
Keep the substrate moist until roots have formed. You can then plant the cuttings singly or in small groups.
What is the Best Time for Planting Tuberous Begonias?
The best time to plant tuberous begonias is in May when the danger of late frosts has passed. If you want to be on the safe side, wait until mid-May. After this date, you can leave potted plants on the balcony and terrace.
The Right Planting Distance for Tuberous Begonias
When planting in groups, pay attention to the growth width of the respective varieties. Some tuberous begonias grow spreading.
They require a minimum distance of 16 inches (40 cm) from the nearest neighbor.
Tuberous Begonias in a Pot
Tuberous begonias are ideal for planting in balcony boxes, flower pots, and hanging baskets.
If you place several tuberous begonias in a wide balcony box, make sure there is a distance of 8 inches (20 cm) between the plants. This way, they won’t be too crowded and will be able to develop healthily.
Watering Tuberous Begonias
Tuberous begonias do not like waterlogging, as it quickly leads to root rot. Collected water in the saucer should therefore be poured off directly.
Water the plants sparingly. Short dry spells do not cause them any problems. When watering, make sure that the leaves and flowers do not catch any water. Water the plants directly at the tuber.
Pruning Tuberous Begonias Properly
Pruning measures are reduced to a minimum for tuberous begonias. More important than pruning is the regular cleaning out of withered flowers and leaves.
This measure supports vitality and stimulates new flower formation. Dead plant parts rot quickly among the densely growing plants, making them more susceptible to disease.
When you take the tubers out of the ground for overwintering, cut the withered plant parts down to a few inches.
Fertilizing Tuberous Begonias
In order for the flowers to shine in all their glory, you can regularly administer fertilizer to the plants.
Liquid fertilizer for balcony plants is ideal. Add the fertilizer to the watering water every 14 days. After the flowering period, reduce the amount of fertilizer slowly.
Overwintering Tuberous Begonias
The ornamental plants are not hardy and die already at frosty temperatures just below 32 °F (0 °C). From the end of September, completely stop watering and fertilizing, allowing the soil to dry. Get the tubers out of the substrate and clean them with a fine brush.
Place the rhizomes in a box filled with sand and put them in a dry and frost-free place with temperatures between 41 and 45 °F (5 and 7 °C). The tubers should be stored in the dark so that they are not stimulated to germinate in the winter.
Fungal Attacks in Tuberous Begonias
Under unfavorable conditions, tuberous begonias can be attacked by fungi.
When planting, make sure that the tubers are not too close together. Poorly ventilated plant groups increase the risk of fungal attack. A location that is too warm can also cause spores to spread.
Under excessively wet conditions, there is a risk that fine roots and rhizomes of tuberous begonias will rot.
Fungal spores settle in these places, often surviving in the substrate. They penetrate the plant organism with their mycelium and further weaken the plant.
As a result, the plant can no longer supply itself with sufficient water and nutrients, so the leaves wither. Remove infested plants as soon as possible so that the spores do not spread to other plants.
This fungus is common in gardens and multiplies under dry and warm conditions. It causes a mealy coating on the tops of leaves that is easily wiped off by hand.
If the fungus spreads its root system further, leaves turn brown from the edge to the center.
A good first countermeasure is to thin out infested plants. But if the fungus has already spread extensively, you should remove the entire plant.
Weakened plants are preferentially attacked by pests. You should not overfertilize the plants and provide them with optimal site conditions so that they can develop vigorously and healthily. Plant extracts can support vitality.
These pests, which are only a few millimeters in size, overwinter on plants in the egg stage and hatch in the spring. The first generation forms immaturely so that the plant is occupied by numerous animals within a short time.
They suck the plant sap from the veins and leave sticky secretions on the leaves. Spray the plants with a mixture of water and dishwashing liquid and wipe off the pests with a cloth.
These pests leave lesions on the leaves through which air enters the tissue cells. Silvery to white shimmering spots develop in these areas. A heavy infestation of pests leads to growth disturbances.
You can recognize an infestation by brown fecal pellets that accumulate on the leaves. Crippled shoots may also be a sign.
Spray the leaves with lime-free rainwater and make sure the air is not too dry. Neem oil has been shown to be preventative.
This beetle lays its eggs on the substrate. When the larvae hatch, they burrow into the substrate and feed on the roots.
Adult insects eat typical patterns in the leaves. They are crepuscular and nocturnal and drop from the plant when threatened.
Nematodes can kill the larvae in the soil, while you can use special traps to catch the beetles themselves.
- Crispa marginata: This variety blooms from June to November and flowers in bright yellow and pure white with red edges.
- Marmorata: This is a large-flowered variety that flowers red and white marbled. The height of growth is between 6 and 12 inches (15 and 30 cm).
- Cascade: Continuous bloomer with drooping shoots. Flowers white. Grows 6 to 12 inches (15 to 30 cm) high.