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Begonias: How to Start Off Corms and When to Plant

Published on March 5th 2021

by AlanGardenMaster. All rights reserved

A close up of a Begonia flower
It's important to start Begonia corms into growth early in the year, and in this story, I will tell you why and how to do it

Not all Begonia are the same

  • Although they may appear similar, some Begonia possess different rooting structures.
  • Some Begonia plants possess root storage organs, known as corms, sometimes referred to as tubers.
  • Fibrous rooted bedding begonias, indoor houseplant begonias and tropical Begonia tend not to produce a corm. Indeed, many of these do not even have a dormant phase.
Find Begonia houseplants on Candide.
  • In this article, I will be concentrating on the Begonia plants that produce corms.

Learn more about Begonia plants:


Begonia spp.


A close up of a Begonia plant
Many indoor Begonias, such as Iron Cross Begonia, have no corm

Begonias with Corms

  • Those begonias that produce the showiest and largest flowers tend to have corms.
A group of colorful Begonia flowers
Show Begonia are grown from corms
  • You can readily buy corms from garden retailers during late winter. Once bought, they should be stored in a frost-free place until planted.
A Begonia corm
A Begonia corm in autumn

Starting Off Begonia Corms

  • Corms are curious-looking storage organs, and it is hard to determine which side is the top and which is the bottom!
Begonia corms
Large Begonia corms
  • Look for an indented concave side. This is the top, and sometimes you can actually see shoots beginning to grow in this hollow.
  • The underside of a corm is rounded (convex), and that is where the new roots will grow from.
  • Because this type of Begonia is not frost hardy, you shouldn't plant it outside straight away. These need starting off with some protection.
  • Fill a seed tray with moistened peat-free potting compost. Place your corms so that the convex side is down. Slightly push the corm into the compost so that there is a good contact.
  • Place the tray on a warm windowsill, a conservatory or heated greenhouse.
  • Ensure that the soil remains moist at all times but also isn't too wet.
New shoots will grow from the corm's indented top and might need protection against slugs and snails.
Begonia Starshine Trailing in a hanging basket

When to Grow Begonia Corms Outside

  • When roots and shoots are well established, transfer corms into individual pots filled with potting compost. Grow these on in a frost-free and well-lit place.
  • You can safely plant Begonia plants outside in late May or June.
Begonia Glowing Embers
Begonia Golden Embers
  • In autumn, the top growth will gradually die back with the shoots' goodness starts migrating back into the corm.

Has this article left you feeling inspired? Look for Begonias and other ornamental plants on Candide.

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