Rhizomatous begonias are the largest group in cultivation. There are well over 700 known species and hundreds of cultivars both named and un-named. As the name suggests, these begonias have a rhizome that is essentially a thickened stem.
The leaves of rhizomes are very diverse in both size and shape and mostly come from Mexico, Central and South America and more recently, Asia. These plants bloom once a year, usually in late winter or early spring, producing a gorgeous flower cluster of very graceful habit. Whether in flower or not they have a spectacular display of foliage.
Light: Most rhizomatous begonias will flourish outdoors in our warm climate provided we locate them in filtered sunlight. Often large trees, especially deciduous ones, offer the right amount of light as do properly constructed shade houses.
Potting and Potting Mediums: In their natural habitat they grow in shallow leaf litter and therefore these shallow-rooted plants require shallow containers. They should never be ‘over-potted’ – into pots with too much soil that will therefore hold too much water. Rhizomes prefer a porous, well-drained medium.
Temperature: With few exceptions, rhizomatous begonias enjoy temperatures in the range that humans find comfortable (20º C – 25º C).
Humidity: Rhizomatous begonias are not particularly demanding and will tolerate lower humidity than a lot of other begonias. A good rule of thumb is the more exotic or distinctive the foliage the more humidity is required.
Watering: As with other begonias – do not over water. The rhizome itself acts as a water storage basin for the plant.
Fertilising: Only fertilise when the plant is growing, usually in the Spring and early Summer. A regular dose of low strength liquid fertilizer is preferred.
Propagation: Rhizomatous begonias can be propagated by three methods: stem cuttings, leaf cuttings and seed.
- Stem cuttings: Use sectional pieces or ends of rhizomes. Plants will develop in a shorter period of time using this method.
- Leaf cuttings: This is the most popular means of propagating and can be done using a whole leaf or leaf wedges.
- Seed: Only use the seed of species to get true to type plants.
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