Begonias are a diverse group of plants, cherished for their vibrant flowers and striking foliage. They offer a wide range of choices, from bedding plants to houseplants, making them a versatile addition to many settings. Their beauty and variety contribute to their widespread popularity.
Types of Begonias
Begonias are broadly categorized into three primary groups based on their root systems and growth habits. While all begonias have fibrous roots, some also possess specialized storage structures like tubers or rhizomes.
Tuberous begonias are known for their large, showy flowers, typically growing from round, fleshy tubers. These varieties often produce blooms up to six inches across in a wide array of colors, including white, pink, red, yellow, and orange. They are commonly grown as annuals in cooler climates, as their tubers are frost-tender and often stored indoors over winter.
Fibrous-rooted begonias, also frequently called ‘wax’ begonias or Begonia semperflorens, are characterized by their continuous blooms and a compact, bushy growth habit. Their leaves are often glossy and rounded, appearing in shades of green, bronze, or reddish-brown. These begonias are a popular choice for bedding plants and containers due to their ease of care and ability to thrive in partial shade to full sun.
Rhizomatous begonias are primarily valued for their ornamental foliage, which exhibits an incredible diversity of shapes, patterns, and colors, including shades of green, red, purple, silver, and bronze. These plants grow from thick, creeping stems (rhizomes) that typically lie on or just below the soil surface. While they do produce flowers, the blooms are generally less prominent than their striking leaves, making them popular as houseplants.
Begonia Care Guide
Light Requirements
Begonias thrive in bright, indirect light. Filtered sunlight, such as near a north or east-facing window indoors, is ideal. Too much direct sunlight, especially intense afternoon sun, can scorch leaves, causing brown spots. Insufficient light can lead to leggy growth, sparse foliage, and reduced flowering. Some fibrous varieties, like wax begonias, can tolerate more direct sun in cooler climates.
Watering Practices
Proper watering is essential for begonia health; they prefer consistently moist soil but are susceptible to root rot if overwatered. Water when the top inch or two of soil feels dry. Ensure water drains freely from the pot to prevent waterlogging. Avoiding water on leaves helps prevent fungal diseases like powdery mildew, especially for Rex and Tuberous begonias. Adjust watering frequency based on environmental factors, requiring less during cooler, dormant periods.
Soil Preferences
Begonias flourish in a well-draining potting mix rich in organic matter. A slightly acidic soil pH (5.5-6.5) is preferred for optimal nutrient uptake. A suitable homemade mix can consist of equal parts peat moss, perlite, and vermiculite, with compost for added nutrients. Peat moss retains moisture and promotes aeration, while perlite and vermiculite improve drainage and prevent compaction. For container-grown begonias, a high-quality all-purpose potting mix or one designed for African violets is effective.
Temperature and Humidity
Begonias prefer moderate temperatures, ideally 65°F to 75°F (18°C to 24°C). They are sensitive to sudden temperature fluctuations and cold drafts, which can cause stress and leaf drop.
As tropical plants, begonias require moderate to high humidity, around 50-60%. Increase humidity by placing plants on pebble trays filled with water, ensuring the pot does not sit directly in the water. A room humidifier is also effective, especially during dry indoor winter months. Misting provides temporary humidity but requires care to avoid prolonged leaf wetness, which encourages fungal issues.
Fertilizing
Regular fertilization during the active growing season promotes healthy growth and abundant blooms. A balanced liquid fertilizer, such as a 20-20-20 N-P-K formulation, applied every two to four weeks, is recommended. For tuberous begonias, a fertilizer with a slightly higher nitrogen and potassium content (e.g., 20-10-20 ratio) supports lush foliage and vibrant flowers.
Dilute liquid fertilizers according to package instructions to prevent over-fertilizing, which can lead to leaf burn and reduced blooming. Always apply fertilizer to moist soil to prevent root damage. During the dormant season, fertilizing should be reduced or stopped.
Pruning
Pruning begonias maintains their shape, encourages bushier growth, and promotes continuous flowering. Removing spent flowers (deadheading) redirects the plant’s energy from seed production to new blooms. Leggy stems, stretched and sparse due to insufficient light, can be pinched back for more compact growth.
For young plants, pinching off new growth tips a few weeks after planting stimulates bushiness. Remove any yellowing, damaged, or diseased leaves to improve air circulation and overall plant health. Clean, sharp pruning shears or fingers can be used.
Propagating Begonias
Propagating begonias is a rewarding way to create new plants. Stem cuttings are a widely used method for most begonia types. To take a stem cutting, select a healthy, non-flowering stem 4 to 6 inches long and cut just below a node. Remove any leaves from the bottom portion that would be below the soil line. The cutting can then be placed directly into a well-draining potting mix or rooted in water before planting.
Leaf Cuttings
Leaf cuttings are particularly effective for rhizomatous begonias, including Rex begonias, which are known for their striking foliage. A healthy, mature leaf can be taken, and the main veins on the underside can be scored or cut. The leaf is then laid flat on a moist potting mix, ensuring good contact with the soil. Roots and new plantlets will eventually form along the cut veins.
Division
Division is another method, primarily used for tuberous or rhizomatous begonias. For tuberous types, dormant tubers can be divided in early spring, ensuring each section has at least one ‘eye’ or growth bud. Rhizomatous begonias can be divided by cutting sections of their fleshy rhizomes, each with a few leaves attached, and replanting them. Regardless of the method, maintaining high humidity and consistent moisture around the cuttings or divisions will help encourage successful rooting.
Common Begonia Problems and Pests
Begonias can encounter several issues, from environmental stressors to pest infestations. Yellowing leaves often indicate overwatering or underwatering, as both extremes disrupt water uptake. Brown leaf tips signal low humidity, while leggy growth points to insufficient light. A lack of blooms may stem from inadequate light, improper fertilization, or a need for deadheading.
Pests
Pests that commonly affect begonias include spider mites, mealybugs, and aphids. Spider mites are tiny pests that create fine webbing on leaves, leading to speckled or yellowed foliage, especially in hot, dry conditions. Mealybugs appear as white, cottony masses, often found in leaf axils or on stems, causing stunted growth. Aphids are small, pear-shaped insects that cluster on new growth and the undersides of leaves, secreting a sticky honeydew.
Treatment
Treating these pests often involves physical removal, such as wiping them off with a damp cloth, or using insecticidal soap or neem oil. Ensuring good air circulation and avoiding overwatering can help prevent fungal diseases like powdery mildew and botrytis, which manifest as white patches or gray mold on leaves and stems. Root rot, a serious issue, is typically caused by persistently wet soil and can be identified by mushy, blackened roots.
Begonia Toxicity
Begonias are toxic to pets, including dogs and cats, if ingested. The plant contains insoluble calcium oxalates, which can cause irritation when chewed or swallowed. Symptoms in pets may include oral irritation, excessive drooling, vomiting, and difficulty swallowing. The highest concentration of these toxic compounds is in the tubers and roots. While generally not listed as toxic to humans, ingestion can still cause mild irritation. Due to potential discomfort in pets, place begonia plants out of reach of curious animals and children. If ingestion is suspected, consult a veterinarian or poison control center.