Begonia grandis Seeds | Hardy Begonia
LATIN NAME: Begonia grandis
COMMON NAME: Hardy Begonia
Plant Profile
Most begonias survive a hard winter only in a greenhouse, but this one has a second way of travelling that has nothing to do with seed. In late summer Begonia grandis makes small pink-scaled bulbils in the axils where the leaf stalks join the stem. They ripen as the stem collapses, drop around the parent and lie through the cold months before sending up a leaf of their own, so an old colony walks slowly outward and downslope.
The leaf is the signature of the family: broad, olive-green above and often flushed red beneath, with the base drawn out on one side so the blade is visibly lopsided about its midrib. That asymmetry is not a defect but a begonia rule, produced by uneven growth of the two halves of the leaf primordium. The flower spray is unequal in the same way, with broad outer tepals and narrow inner ones.
The plants are monoecious, and the two flower forms are easy to separate once you look underneath. A male flower has four tepals and a cluster of yellow stamens. A female flower sits above a three-winged ovary, one wing usually longer than the other two, and the wings persist on the dry capsule. That unevenly developed ovary is diagnostic of the genus.
In the ornamental garden the hardy begonia belongs in cool shade with humus-rich soil that never dries out completely, and it is most effective planted in quantity beneath shrubs, where the red leaf undersides catch a low sun. Under a tree it spreads by its own bulbils into gaps between roots where digging is awkward, and seedlings appear in damp corners. In containers it works well with ferns. In a cold garden the top growth goes down at the first hard frost, so mark the spot with a label or a low stone, since nothing shows above ground through the winter.
Science & Biotechnology
Begonias are exceptionally easy to multiply in vitro and correspondingly common in tissue-culture laboratories. Leaf-disc culture is the standard method: small squares of leaf are placed on a cytokinin-rich medium, shoots regenerate directly from the cut surface, and the shoots are rooted on a low-auxin medium and hardened off under mist. The genus runs on a base chromosome number of thirteen, and structural rearrangement rather than number separates many species.
Uses & Benefits
A begonia stem tastes sharp because the plant accumulates soluble oxalate in the cell vacuoles. In parts of East Asia the young stems and leaves of this species are eaten cooked rather than raw, the cooking water being discarded. The same chemistry is why the sap irritates some skins, and it is worth washing hands after dividing clumps or pricking out.
Growing from Seed
The species comes from shaded woodland ground in central and southern China and in Japan, growing in leaf litter over rock and in the shelter of taller perennials. It is one of the hardiest begonias in cultivation and succeeds in the open where the fibrous and cane begonias would not last a winter. It behaves as a herbaceous perennial, building foliage through summer and flowering into autumn.
What survives the winter is a swollen fleshy base at or just below soil level, with buds that push a new stem when the ground warms. The stem itself is thick and watery and collapses completely rather than dying down gradually, which is normal and not a sign of trouble. Gardeners who cut the stems early lose the bulbils before they have ripened and shed.
Begonia seed is dust-fine, no larger than a speck of sand, and it must never be buried. Fill a pan with finely sieved compost, firm it and water from below with a fine spray. Tap the seed thinly over the surface from a folded paper, cover the pan with glass or a clear lid, and keep it shaded with even moisture. The first result is a green film of tiny leaves.
Handle the seedlings with a small forked stick once the first true leaves have opened, lifting a clump with its root ball intact into a tray of similar mix at a spacing of a couple of centimetres. Keep the trays shaded and humid and water from below. Move the young plants into individual pots when the leaves overlap, then plant out once the stems have thickened.
Our Take
Start this one from bulbils if you can get them, because the young plants are quicker to size and much easier to handle than the seed; if seed it must be, sow it on the surface and be patient with the pricking out. Our guides to begonia seed, to the Jack-in-the-pulpit arisaema and to Solomon’s seal cover companions for the same damp shade.
Related Reading
Gardeners who grow Hardy Begonia often pair it with these related subjects: