About the iron cross begonia
The iron cross begonia (Begonia masoniana) is grown mainly for its leaves rather than its flowers. The leaves are puckered, covered in fine reddish-brown hairs, and marked with a dark pattern in the center that is said to resemble an iron cross. It is a rhizomatous begonia, meaning it grows from a creeping stem at or just below the soil surface. It is often grouped with rex begonias, though it is classed separately. Care is similar to other rhizomatous begonias, with a few details that matter.
Light
Give it bright, indirect light. An east window, or a spot set back from a south or west window, works for many homes. Direct midday sun can scorch the leaves and fade the pattern, while low light leads to leggy growth and dulls the leaf markings. Early morning or late-day sun is gentler than midday sun.
Watering and signs of overwatering
Water when the top of the mix feels dry to the touch, then water thoroughly and let the pot drain. Use a pot with drainage holes and do not leave it standing in water. Because the plant has a rhizome and thick, hairy leaves, it is more prone to rot than to drought.
Signs of overwatering include:
- Yellowing leaves, particularly lower ones
- Soft, mushy or blackened stems or rhizomes
- Leaves that wilt even though the mix is wet
- Fungal spots or a grey, fuzzy mold on leaves (a sign of botrytis) or white powdery growth (mildew)
- A sour smell from the pot
Try to water the soil rather than the foliage. Wet hairy leaves can stay damp and develop spots. Water more lightly in winter, when the plant grows more slowly and may go partly dormant.
Humidity, temperature and airflow
Begonias like moderate to high humidity but dislike sitting in stagnant, wet air. A humidifier or grouping plants helps without wetting the leaves, and some air circulation helps prevent mildew. Normal room temperatures suit it. A general guideline is to avoid exposing it to temperatures below roughly 50 F (10 C), and to keep it away from cold drafts, heaters and air conditioning.
Soil, pots and feeding
Use a light, airy, well-draining mix, such as potting mix with added perlite or bark. Rhizomatous begonias have shallow roots, so a relatively small, shallow pot is usually better than a deep one. Overpotting keeps soil wet too long. Repot when the rhizome has outgrown the container, typically in spring.
Feed lightly during the active growing period with a diluted balanced fertilizer. Do not feed dry soil, and do not push a dormant plant. Weak and regular is safer than strong and occasional.
Flowers
Iron cross begonia does flower, usually with small pinkish or whitish blooms on upright stalks in spring, but the flowers are modest compared with the foliage. Some growers remove the stalks so the plant puts its energy into leaves, though that is optional.
Propagation: water or soil?
Begonia propagation works well from leaf cuttings and rhizome division, and the safest medium is usually a light, moist mix rather than water. Leaves and thick stems are prone to rot in water, so soil or a perlite-and-peat style mix kept in a humid environment tends to be more reliable, although stem cuttings can sometimes root in water.
- Leaf cuttings: A whole leaf with a short stalk can be laid or planted in a light mix, or a leaf can be cut into wedges that each include a main vein. Keep it warm, humid and bright but not in direct sun. A clear lid or bag helps. New plantlets can take weeks to months.
- Rhizome division: In spring, cut the rhizome into sections, each with a growing point and some roots, and pot them separately.
- Hygiene: Use clean tools, and remove any cutting that turns mushy.
Why begonias can be hard to grow
Many begonias fail for the same few reasons: soil kept too wet, humidity combined with poor airflow, and light that is too low or too harsh. If the plant gets too cold it may suddenly collapse. Once you find the right balance of bright light, careful watering and gentle airflow, the iron cross begonia is generally manageable for an attentive grower, though not a forgiving plant for beginners.
Toxicity
Begonias are generally considered toxic to cats, dogs and people if eaten, because they contain insoluble oxalates, and the underground parts are usually described as the most concentrated. Chewing can cause mouth irritation, drooling and vomiting. Keep the plant out of reach of pets and young children, and contact a veterinarian, doctor or poison control service if any is eaten. If you want a plant generally listed as non-toxic, see the goldfish plant care guide.