Begonias can be propagated with tubers or cuttings, or they can even be grown straight from corms. Corms are essentially the same as tubers, but are closer to bulbs in that they’re distributed in the same way—partially dried, often in sacks or lots, and are ready to plant.
There are important things to remember when you’re planting corms, and one is to keep the concave side up and make sure no water sits in the divet. Another is to keep the corms heated when you plant them. These two things are what will decide what you should have when you plant your begonia corms.
Step 1 – Ready Tray
The first thing you should do is get your tray ready. Fill up your holes in the tray with your peat moss or compost and make sure you mist it with a little bit of water from a spray bottle. Make sure you use warm water, to start the soil off right with a temperature that will be more conducive to corm growth.
Step 2 – Plant Corms
Your tray is now ready for corm growth. Plant begonia corms concave side up, slightly above or level with the planting soil in which you’re placing them. After you adjust the corms, gently press down the soil and water them promptly. Don’t drench them though, and make sure you don’t get any water into the depressions in the corms. Getting water in the corms can cause them to rot and consequently not to sprout at all.
Step 3 – Place Planting Tray
Now that you have your corms planted, put the planting tray either on a heated propagator for keeping the corms heated, or put the entire tray in a sunny spot for the same purpose. If you don’t have the time to constantly check the soil for moisture levels, you can put a lid on the tray as long as it’s ventilated.
Step 4 – Transplant Begonias
After a few weeks, your begonias will sprout roots and little shoots. It’s time to transplant them into larger pots for more advanced care. Tenderly lift the infant plants out of the tray and transplant them, peat moss and all, into a pot filled with fine potting soil and drainage additives such as sand. Or, you can plant them into a flower bed with well-drained organic soil. In a flower bed, space them about 10 to 18 inches apart to avoid any tangling of roots. Also, you want to give the plants enough ventilation and air circulation to prevent any mildew or rot from harming them and killing them. The flower bed shouldn’t have full sunlight either, so make sure there’s partial shade for your flowers before you even put them there.
That’s it. Come fall, just reduce your watering to get the plants ready for dormancy or for overwintering indoors. Enjoy your begonias and enjoy the ease of growing them from corms.