Rieger begonias are herbaceous plants belonging to the order Cucurbitales, genus Begonia, and family Begoniaceae. Rieger begonias have fibrous root systems, robust plant shapes, and single, alternate, asymmetrical heart-shaped leaves.
The leaves are usually a lush green, occasionally with shades of reddish-brown. The flowers are diverse, often double-petaled, and come in a variety of colors such as red, orange, yellow, and white. The large, vibrant blooms, unique in their form, color, and fragrance, bloom for a long time, from December through to April of the following spring.
The blooming period peaks from April to June and from September to December. Rieger begonias prefer a warm, moist, semi-shaded environment and are found in tropical and subtropical regions.
They are ideal ornamental plants, given their long blooming period, rich colors, lush green foliage, and robust forms. They are excellent choices for indoor beautification in winter and are one of the main types of indoor flowering plants for all seasons.
Rieger begonias are perennial herbs. The plant typically grows to less than 40 cm high, with no evident tuberous parts underground, but rather a semi-tuberous, fibrous root system. The stems are green, with enlarged nodes, and the fleshy, juicy branches are brittle and tend to stand upright or slightly droop.
The single leaves are alternate, oval or asymmetrical heart-shaped, with sharp tips and a skewed base. The leaf edges are bluntly serrated or notched, with numerous palmate veins. The leaf length is approximately equal to its width, and the leaf diameter is around 10 cm.
The leaf surface is smooth and dark green, with a waxy texture. The flowers are large and vary in form, with colors of red, white, yellow, orange, and pink in single or double-petal varieties. The flowering period is from autumn to winter.
Leaves: Single, alternate, skewed base heart-shaped leaves, with bluntly serrated or notched edges, palmate veins, smooth and waxy surface, and dark green color.
Flowers: Short-day blooming plants, double-petaled, with colors of red, yellow, white, and orange. The flowering period is in winter.
Rieger begonias prefer a warm, moist, semi-shaded environment.
Rieger begonias are found in tropical and subtropical regions. Originating in Germany, they are cultivated in southern China. They prefer a warm, moist, well-ventilated environment.
The requirements for light, temperature, water, and fertilizers are relatively strict, and they do not tolerate stuffy heat and direct sunlight. The optimal growing temperature is between 15-22℃. In winter, the temperature should not drop below 5℃.
In the high temperatures and heavy rains of summer, they should be sheltered from outdoor rain and standing water to avoid stem rot and wilting. They thrive best in loose, fertile, well-drained, slightly acidic sandy loam.
Rieger begonia seeds are tiny, requiring a small-seed sowing method. The seeds are generally imported and come in two varieties: coated and uncoated.
Coated seeds can be sorted and sown in plug trays, while uncoated seeds are sown in seedling trays. The sowing substrate is a mixture of one part each of peat and vermiculite, which is crushed, sterilized, mixed, and moistened for use.
Peat repels water when dry, so it should not be used in a dry state. When sowing, the substrate is placed in the seedling tray and thoroughly watered with a spray bottle.
Coated seeds can be sorted with tweezers, one seed per hole, non-coated seeds can be mixed with a suitable amount of fine vermiculite powder and broadcast in the seedling tray. After sowing, there’s no need to cover with soil, just spray with a fine watering can, then wrap the seedling tray in transparent plastic film. In an environment around 20°C, seedlings will start to emerge after 12 days. When the seedlings grow true leaves, they can be ventilated appropriately to promote root growth. The seedlings grow slowly within the first three months. For seedlings sown in early summer, there’s no need to remove the plastic film throughout the summer, as the seedlings can tolerate high humidity and high temperatures. After the cool weather in late autumn, the plastic film can be gradually removed to harden the seedlings, and they can be potted by early winter. Use a smaller flower pot with multiple holes at the bottom, the culture soil can be a mixture of two parts peat soil and one part vermiculite (or one part plain sand). Control watering before potting to keep the culture soil in the seedling tray semi-dry to avoid root damage due to clumping when the seedlings are removed.
At the end of autumn and beginning of winter, when pruning and shaping the plant, the pruned new branches can be used for cuttings. Begonia can be propagated by stem or leaf cuttings. When preparing stem cuttings, the length of the branches should be appropriate, and the lower part of the branch should be cut into a horseshoe shape with a blade.
When preparing leaf cuttings, choose vigorously growing, semi-mature leaves, and cut the lower end of the leaf stalk at an angle with a blade. The cutting medium should be vermiculite or plain sand. After inserting the cuttings, water thoroughly, but do not allow water to accumulate on the leaf surface.
Cover with plastic film and place in a location with diffused light, ventilate appropriately, and avoid high temperatures. After about three weeks, the cuttings should root.
When new leaves begin to grow, this indicates rooting has occurred. Plants obtained through stem cutting do not have underground tubers.
After three weeks, the lower part of the leaf stalk can also grow adventitious roots, but it will take another month and a half for adventitious buds to grow from the lower part of the leaf stalk and gradually emerge from the soil.
The tissue culture method is a fast way to obtain a large number of seedlings. During the growing season, well-developed leaves are used as explants.
In a certain culture medium, a large number of virus-free seedlings can be obtained through the culture of non-toxic explants, subculture and rooting culture. This method requires a large investment and is only used in large-scale production.
Begonia likes well-drained substrate. Peat soil, vermiculite, perlite, carbonized tree bark, pine needles and other substrates can be selected. The principle of blending is that the ratio of organic to inorganic matter is 3:4, and the pH value is 5.2-6.5. For example, peat soil: vermiculite: perlite = 3:3:1, or high-fiber peat soil: perlite in a ratio of 3:2.
You can also choose to use the commercially available substrate specially designed for potted begonia. Before potting, the substrate should be sprayed and disinfected with 1000 times carbendazim solution. Use a standard round-edged plastic pot with multiple holes, 10-14 cm in size, with one plant per pot.
When transplanting, carefully remove the seedling from the hole tray, minimizing mechanical damage to the seedling’s roots and leaves. Gently place the seedling in the pot, add substrate around the seedling, and gently press it along the edge of the pot.
Do not press down on the base of the seedling to avoid breaking the roots. After potting, place in a greenhouse cultivation rack, water thoroughly once, pour roots with 1000 times carbendazim solution, and manage in shade.
In the hot summer, pay attention to spray cooling, which is conducive to the growth of new roots and leaves. At the same time, turn the pot every 15-20 days, and adjust the leaf layer every 5-7 days, so that the plant receives uniform light and avoids biased crowns.
The begonia ‘Elatior’, a short-day plant, thrives in scattered light and dislikes direct sunlight. The optimal light intensity for it ranges from 8000 to 25,000 lx.
During the seedling stage, light should be limited to below 10,000 lx. In the medium seedling growth stage, the light intensity can be around 18,000 lx. During the bud differentiation stage, intensity can be increased to 25,000 lx, promoting darker green leaves and brighter flowers.
During blooming, light should be reduced to below 25,000 lx to prolong shelf life. In summer, with outdoor light intensity as high as 60,000 to 80,000 lx and greenhouse temperatures above 25°C, shading of over 70% is necessary.
Once temperatures decrease in late October, light exposure can be increased. Mid-November onwards, when greenhouse temperatures are around 23°C, ample light should be provided to produce high-quality potted flowers.
The ideal growth temperature for the begonia ‘Elatior’ is 15-23°C. For newly potted seedlings, daytime temperatures should be maintained at 23°C and nighttime at 18°C.
A steady 20°C during the growth period is ideal for nutritional growth, while 18°C during blooming prolongs the lifespan of each flower. The begonia ‘Elatior’ is intolerant to both low and high temperatures.
Growth will stagnate and flowers will drop if temperatures drop below 12°C. Above 28°C, diseases are likely to occur, or leaves may lose their green color. Growth will halt over 32°C. In summer, when temperatures exceed 24°C, shading should be considered.
If temperatures rise over 24°C, excessive growth may occur, resulting in fewer buds and small flowers. Night temperatures in autumn and winter should be maintained at 18-20°C to ensure the quality of the potted flowers.
The begonia ‘Elatior’ prefers a moist environment but dislikes being waterlogged. The “see dry, see wet” principle should be followed when watering. Avoid wetting the leaves.
Professional cultivation usually involves tidal irrigation or drip irrigation. The begonia ‘Elatior’ requires high air humidity, ideally 80-85%. Relative humidity should be kept at 70-85% before and after the initial growth phase.
In the southern regions of China, water should be sprinkled on the ground at midday to increase air humidity. In the drier northern regions, it’s important to increase humidity in the greenhouse, ensuring leaves are dry by sunset. When the plant enters the reproductive growth phase, maintain humidity at 65-75%.
After buds appear, lower the relative humidity to 55-75% to prevent diseases, especially powdery mildew and grey mold. Ensure good air circulation to prevent dew condensation on leaves.
The begonia ‘Elatior’ has strict fertilization requirements. The EC value of the substrate should not exceed 1.5 ms/cm, or it may cause fertilizer damage. Fertilizer content and concentration should be adjusted according to growth stages.
For newly potted seedlings, the first fertilization should be a dilute liquid fertilizer, primarily nitrogen-based. As the plant grows, adjust the nitrogen, phosphorus, and potassium content of the fertilizer.
During the nutritional growth phase before bud differentiation, apply a 15-15-15 or 20-10-20 compound fertilizer, or use a special begonia ‘Elatior’ fertilizer, once a week at a concentration of 2500-3000 times dilution.
From bud differentiation to flowering, increase the use of phosphorus and potassium fertilizers at a concentration of 1500-2000 times dilution, once a week.
During the entire growth process, foliar fertilization should be carried out every 20 days, but try to avoid it after the buds appear to ensure the leaves stay green. Drip irrigation can be used, mixing in fertilizer with watering.
The Begonia Rex has a degree of branching. For those with poor plant shape, artificial pinching can promote the sprouting of side branches.
Generally, two weeks after potting the seedlings, when the 3rd to 4th leaf of the plant unfolds, the top bud is removed to encourage the base to sprout side branches, making the plant shape fuller.
As Begonia Rex will generate flower buds during the seedling stage, it is necessary to remove excess flower buds in time to reduce extra nutrient consumption, extend light time to promote nutritional growth, and make the plant shape more neat and beautiful.
During the entire growth process, leaves should be sorted out in time, flower buds thinned, and diseased and old leaves removed. The plant should also be rotated every 2-3 weeks to ensure even light exposure and a full and symmetrical shape.
Begonia Rex can be cultivated year-round. Depending on the season, climate, and light intensity, the growth cycle of Begonia Rex is generally 13-19 weeks.
In production, when the cultivation environment reaches 14 hours of daylight, nutritional growth can be maintained. When daylight is less than 10 hours, short-day treatment for more than 3 weeks can complete flower bud differentiation, and flowers can bloom around 6 weeks.
Therefore, the process from seedling cultivation, planting, nutritional growth, light adjustment to delay or advance flower bud differentiation can be formulated according to the target flowering period to achieve the purpose of artificial control.
Once the plant reaches the standard, short-day treatment generally starts 14 weeks before the target flowering period. Black plastic film or black shading net can be used to darken and promote flowering, with a dark period temperature of 18-21℃.
When the temperature is high, the dark treatment time can be adjusted to 18:00 to 9:00 the next day. During flowering promotion, generally first 2 weeks of light for 6-8 hours, then darkness for 15 hours, followed by 2 weeks of light for 8-10 hours, darkness for 14 hours.
Once flower bud differentiation appears in the plant, continue with 2 weeks of light for more than 10 hours, darkness for 13 hours. At this time, flower bud differentiation is completed, and after 6-8 weeks of cultivation, the plant can bloom and be marketed.
Aphids: Cause leaf deformation, with yellow spots on top.
Nematodes: Cause the leaf tip to have a slight red color, the veins in the middle of the leaf become smooth and gray.
Thrips: Cause flowers to fade and newly grown leaves to deform.
Bacterial disease: Rarely occurs if clean raw materials are used, but it is difficult to deal with once it happens. It is recommended to take preventive measures in advance.
Grey mold: Can be prevented by controlling climatic conditions.
Fusarium: Can be easily avoided by propagating healthy plants.
Powdery mildew: Use a sulfur fumigator to spray for 1 to 2 hours every night to prevent the disease. Be careful not to spray for too long as it can damage the flowers.
Physiological diseases: Red leaf disease: Often occurs when watering frequently under high temperatures or strong light. Increasing shade and watering can improve this condition.
Grey spot disease: Generally occurs on the edges of relatively lower growing leaves, or there are many small spots on the underside of the leaves. This is entirely due to a too low pH value or too high ammonium concentration. The concentration and formulation of the fertilizer should be changed.
Leaves with spots: Often occurs on the highest leaves of the plant, possibly due to a too high PH value. Use a mixture of 0.75 mg/kg ammonium sulfate and 0.5 mg/kg potassium sulfate with water and water 1 to 2 times a day. The problem can be effectively controlled after 1 to 2 weeks.
There are fewer pests and diseases when Begonia Rex is grown at home. Regularly spray fungicides to prevent bacterial soft rot and powdery mildew.
You can use agricultural streptomycin 200ug/g or thiodiazinone 1000 times liquid spray; to prevent pesticide pollution in the home, you can make some homemade natural pesticides, the prevention effect is good, there are the following two ways:
(1) Ginger juice with water, spray in a 1:25 ratio, can prevent soft rot and the germination of other pathogenic spores.
(2) 50 grams of dry chili peppers, add 50 times water, boil for half an hour, take the supernatant and spray on the leaf surface, can effectively prevent aphids, red spiders, and top mites, inhibit plant growth, and make new leaves hard or linear.
Ornamental Value: Begonia Rex has a long flowering period, rich flower colors, green branches and leaves, and a full plant shape. It is an excellent variety for beautifying the indoor environment in winter and one of the main types of indoor ornamental plants throughout the year.
Begonia Rex is a widely cultivated ornamental herb with many varieties and rich flower colors. It is mostly used for indoor potting. In southern China, it is also used for garden landscape design, hanging cultivation, or planting along garden paths and grass edges. It is also suitable for ornamental cultivation in flower beds and flower stands.
Peggie was once a high school mathematics teacher, but she set aside her chalkboard and textbooks to follow her lifelong passion for flowers. After years of dedication and learning, she not only established a thriving flower shop but also founded this blog, “Flowers Library”. If you have any questions or wish to learn more about flowers, feel free to contact Peggie.
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