Rhizomatous Begonia (Group)

Basic Information

Common Name: Rhizomatous Begonia (Group)

Scientific Name: Begonia Rhizomatous Group

Native Habitat: Primarily tropical and subtropical regions of the world, with centers of diversity in South America, Southeast Asia, and Africa.

History / Discovery / Cultivator

Rhizomatous begonias, as a group, boast a rich history intertwined with botanical exploration and horticultural innovation. The genus Begonia itself was named by Charles Plumier, a French botanist, in honor of Michel Bégon, a French official who organized an expedition to the West Indies in the late 17th century. While Plumier named the genus, the specific origins of rhizomatous begonias within that vast grouping are more complex. They weren’t a single discovery, but rather a slow accumulation of species brought back from various expeditions to tropical regions.

Rhizomatous begonias are characterized by their creeping, modified stems (rhizomes) that grow horizontally along or just beneath the soil surface. These rhizomes are not roots but stems adapted for vegetative propagation and nutrient storage. It’s from these rhizomes that new shoots and roots emerge, allowing the plant to spread. This unique morphology has fascinated botanists and plant enthusiasts for centuries.

The early 19th century saw increased interest in cultivating exotic plants, fueled by improved transportation and communication. Plant hunters were dispatched to remote corners of the globe, and many rhizomatous begonia species were among their discoveries. Names like Joseph Dalton Hooker, who explored parts of Asia, are associated with the introduction of various begonia species, although directly linking him to specific rhizomatous cultivars requires digging into his collecting notes.

Specific cultivars and hybrids have been developed and popularized by numerous horticulturists and nurseries over time. The development of named cultivars is ongoing, focusing on leaf patterns, textures, and flower colors. It’s often difficult to pinpoint a single “cultivator” for the entire group, as numerous breeders and nurseries have contributed to the vast array of rhizomatous begonias available today. Specific cultivars, like ‘Iron Cross’ or ‘Escargot,’ often have traceable origin stories linked to particular breeders or nurseries but the “Rhizomatous Group” represents an evolutionary and horticultural effort over centuries from plants found globally. The interest in these plants stems from their low maintenance nature, varied leaf texture, and overall striking appearance.

The geographic origins of rhizomatous begonias are as diverse as the plants themselves. They are found in the humid forests of South America (especially Brazil), the cloud forests of Central America, the tropical rainforests of Southeast Asia (including Indonesia, Malaysia, and the Philippines), and parts of Africa. This wide distribution reflects the adaptability of the rhizomatous growth habit, allowing them to thrive in a variety of shaded, moist environments.

Plant Care Summary

Botanical Insights

Adaptations

Rhizomatous begonias exhibit several key adaptations that contribute to their success. The rhizome itself is a crucial adaptation, allowing the plant to store water and nutrients, enabling it to survive periods of drought or nutrient scarcity. It also allows the plant to spread vegetatively, forming colonies in suitable habitats. Their often asymmetric leaves are another adaptation, maximizing light capture in shaded environments. Some rhizomatous begonias have specialized leaf structures, such as hairs or peltate leaves (where the petiole attaches to the leaf within the leaf margin), that help to shed water and prevent fungal diseases in humid conditions. Some species also produce bulbils, small plantlets that develop on the leaves, providing another means of propagation. The diversity in leaf textures and colors may also serve as a form of camouflage or mimicry, protecting the plant from herbivores.

Propagation Methods

Rhizomatous begonias are relatively easy to propagate, primarily through vegetative methods.

• Rhizome Cuttings: The most common method is to divide the rhizome into sections, ensuring that each section has at least one node (where a leaf emerges). These sections can then be planted in a well-draining potting mix.
• Leaf Cuttings: Some rhizomatous begonias can be propagated from leaf cuttings. A leaf is cut into sections, and the sections are placed on a moist substrate, such as perlite or vermiculite, and kept in a humid environment.
• Whole Leaf Propagation: Similar to leaf cuttings, the entire leaf, including the petiole, is placed on a rooting medium. This method often requires scoring the veins on the underside of the leaf to encourage root formation.

Toxicology

Rhizomatous begonias contain insoluble calcium oxalates throughout the plant, particularly in the stems and leaves. If ingested, these oxalates can cause oral irritation, excessive drooling, and difficulty swallowing. In humans, ingestion may lead to a burning sensation in the mouth and throat, as well as possible vomiting. For pets like cats and dogs, the symptoms are similar, potentially including pawing at the mouth and loss of appetite. While not usually fatal, ingestion can be quite uncomfortable. It is recommended to keep these plants out of reach of children and pets, and to wear gloves when handling them to avoid skin irritation. Contact with the sap can cause dermatitis in sensitive individuals.

Common Problems

Pests:

• Mealybugs
• Spider mites
• Aphids

Diseases:

• Powdery mildew
• Botrytis blight (gray mold)
• Root rot

Other:

• Leaf yellowing (Overwatering or nutrient deficiency)
• Browning leaf tips (Low humidity or dry air)
• Leggy growth (Insufficient light)

Rarity & Value

Rarity:

The rarity of a specific rhizomatous begonia cultivar can vary significantly. Some older, less popular varieties might be considered rare simply due to lack of availability. Newer cultivars with unique leaf patterns, colors, or textures, especially those developed by private breeders, may be rare due to limited propagation and high demand. Slow growth rates and difficulty in propagation can also contribute to rarity. Certain cultivars with unstable variegation, meaning the variegation pattern is not consistently passed down through propagation, are also considered rare.

Value:

Several factors influence the market value of rhizomatous begonias. Size and maturity play a role, with larger, more established plants generally commanding higher prices. The quality and stability of variegation, if present, is a major factor. Plants with vibrant, well-defined, and stable variegation are highly sought after. The overall health and appearance of the plant are also crucial; a plant free from pests and diseases with well-formed leaves will be more valuable. Current collector trends and the perceived desirability of a particular cultivar can also significantly impact its value. Provenance, meaning the documented history of the plant and its origins, can also add value, especially for rare or historically significant cultivars.