Begonia × ricinifolia ‘Immense’

A historic hybrid between two tropical American species

Begonia × ricinifolia is an artificial hybrid between B. Barkeri and B. Heracleifolia, first published in 1847. ‘Immense’ is an old, exceptionally large-leaved horticultural form of this hybrid.

Both parent species are native to tropical America. The hybrid arose in cultivation from those two tropical American parents, and ‘Immense’ was retained for its exceptional leaf size.

Indoor care for Begonia × ricinifolia ‘Immense’

Light

A practical home position for Begonia × ricinifolia ‘Immense’ is near a large east window or 1–2 m back from bright south or west glass with hot direct sun filtered. The light is too strong if it heats the leaves and large pale patches appear on the exposed side and cannot be repaired. A position several metres from a window is too dark when petioles become long and weak, the crown leans and new leaves fail to reach their normal breadth. Do not move it into harsher sun just to deepen the colour. Strong healthy leaves display the immense palmate leaf size and sturdy crown naturally. Low light weakens the new leaves, while hot sun scorches the surface.

Watering

Let the upper layer change first, then water Begonia × ricinifolia ‘Immense’ when the top 3–4 cm has dried and the broad pot feels lighter, while the lower root zone remains lightly moist. Water from several points across the surface, continue to runoff and discard the collected water. A deep saturated pot is hazardous because the broad shallow roots require air beneath the rhizome. The substantial rhizome holds reserve, yet a long dry spell sacrifices fine roots and causes the large leaves to collapse. Test several points in the broad pot holding ‘Immense’, because the centre can remain moist after the outer mix has dried. Recheck the lower mix after a move: brighter light speeds drying, while cooler air or a larger pot slows it.

Substrate and roots

Plan the potting mix around a thick surface rhizome with a wide, shallow network of feeder roots. Choose a structurally open blend of peat-free substrate or coir, medium bark and pumice or perlite. Fine heavy compost forms an airless core beneath the large rhizome, especially in an oversized pot. Choose a heavy, broad drainage container that supports the crown without adding unnecessary depth. Width and weight matter more than depth for ‘Immense’. The thick rhizome travels across the surface.

Temperature

Warm, even conditions suit Begonia × ricinifolia ‘Immense’: roughly 18–28 °C, staying above 15 °C. A cold sill can chill the shallow roots before the room thermometer shows a problem. Avoid local heat around one side of the pot, which makes moisture difficult to judge.

Humidity and airflow

Begonia × ricinifolia ‘Immense’ grows best when humidity stays steady. Average household humidity can be sufficient, while 50–70% helps very large leaves open with fewer dry margins. Give each expanding leaf on ‘Immense’ open space and keep it outside the direct stream of a heater. A quiet fan outside an enclosure or normal room circulation is enough. The leaves should not flutter constantly.

Fertilising

Match feeding to visible growth in Begonia × ricinifolia ‘Immense’: use a complete balanced fertiliser at one-third strength every three to five weeks. Continue lightly at any time of year if growth remains steady. Pause when cool conditions stop it. A low regular dose during growth is safer for salt-sensitive Begonia roots than an occasional concentrated application. Do not use extra fertiliser to force leaf size on ‘Immense’. Strong light and a healthy root system must support large growth.

Repotting

Give Begonia × ricinifolia ‘Immense’ fresh mix once the thick rhizome reaches the container edge, the crown becomes unstable, water channels through or the substrate has collapsed. The next pot should be roughly 3–5 cm wider and retain the same basic shape. Preserve the central rhizome and its anchoring roots. Divide only a vigorous outer section with roots and a growing point. Choose a period when roots and leaves are growing, and avoid severe root work in a cold, wet room. Recruit help for a large specimen so the heavy crown and brittle petioles remain supported while the root ball is moved.

Support, pruning, handling and leaf care

Stand Begonia × ricinifolia ‘Immense’ in a heavy broad pot and give every large leaf room to open. Do not bundle the petioles. Guide the thick surface rhizome and prune a damaged leaf cleanly at its base. If one side faces the window, rotate by small steps only after the newest leaf has hardened. Clean an immense mature blade in supported sections, using one hand beneath it and a soft damp cloth above. Never drag the plant by a petiole or allow a heavy wet leaf to fold under its own weight. Prune dead tissue back to a healthy base, taking care not to nick the next bud or leaf.

If Begonia × ricinifolia ‘Immense’ looks unwell

Massive palmate leaves droop or tear

Large mature blades can arch and split under their own weight or after contact. A dry, stable tear is mechanical damage. Stabilise the pot and give the large leaves enough clearance. If a whole leaf suddenly becomes limp, check the root ball. Remove a soft brown tear before decay spreads along the leaf.

Deep lobes brown at their many tips

The numerous points lose moisture before the broad crinkled centre after uneven watering, salt accumulation or a heater draught. Feel the mix and look for salt on the surface, then correct the watering or airflow problem. Keep the large rhizome evenly moist with good drainage. New growth will replace the dead tips.

Hairy stems carry white clusters

The cultivar’s red-brown hairs are evenly distributed along sturdy petioles. Mealybugs form separate cottony masses at joints; scale forms discrete removable bumps and may produce honeydew. Compare several petioles before treating. If cottony masses or removable bumps are present, isolate the plant and treat the pest throughout the large canopy.

A top-heavy, sprawling rhizome

Immense naturally spreads and can lever a shallow root ball out of the pot. Move a healthy plant to a wider, stable container and anchor the rhizome at the surface. Cut away any bend that is dark and soft.

Several giant leaves collapse from one point

Trace the fallen stalks back through the huge canopy. If they all meet at one soft section, cut that part away until the exposed interior is consistently firm and clean. Root the healthy end at the surface and take a leaf cutting immediately when the last healthy growing point is involved.

Handling Begonia × ricinifolia ‘Immense’ safely around pets

Begonia × ricinifolia ‘Immense’, including its broadly lobed palmate leaves, contains soluble calcium oxalates and is toxic to cats and dogs. A pet that chews the leaves or a stem may drool or vomit; exposed roots create the highest risk during repotting. Division can leave small rhizome and root fragments on the work surface. Count and discard every rhizome and root piece before pets return to the area. Keep pets outside the work area until the divided plant, used substrate and tools have been cleared. If drooling, vomiting or swallowing follows contact with the leaves or a stem, contact a veterinarian. Bag discarded roots, spent substrate and cuttings after repotting, then wash hands.

A huge castor-leaf begonia

The epithet ricinifolia means castor-oil-plant-leaved and refers to the broad, deeply lobed foliage. The multiplication sign shows that Begonia × ricinifolia is treated as a hybrid.

‘Immense’ is French as well as English and means enormous. It is an old horticultural name that emphasises the exceptional scale of this rhizomatous begonia’s leaves.