Potting Up Begonia Tubers

Last year for the first time, I tried growing tuberous Begonias, after seeing my blogging buddy Peter The Outlaw Gardener's success with them. I tried a handful, some of which grew well, and some of which rotted (boo). But I had enough success with them, and loved the blowsy, old-fashioned flowers so much, that I bought more recently and potted them up in the greenhouse to sprout and grow on until they are big enough and it's warm enough to put them outside (which could be a while).

I knew it was time to look for them at Watson's Nursery in Puyallup when I noticed that last year's tubers, which had been overwintering in my dark garage, had begun to sprout.

See those little white nubbins? They should be green, and they'll probably turn green now that I've watered them and moved them out to the heated greenhouse. They produce little chlorophyll when they sprout without enough sunlight.

Last year's tubers -- I hope all of them will sprout again

Here's what I bought at Watson's.

6 of these

2 of these

2 of these

And 6 of these

Then, of course, I saw more for sale at the local hardware store.

I potted them up in Miracle-Gro potting soil, which I mix with a big helping of Perlite for drainage (the Miracle-Gro has no Perlite in it). I normally prefer a different brand -- SunGro Horticulture's Black Gold -- but the last two bags of that brand that I bought at Fred Meyer were infested with fungus gnats.

I also wet the soil first, rather than after, using water that I have soaked a Bacillus thuringiensis (Bt) doughnut in (to take care of the fungus gnat problem that I now have). I've found that using water that has Bt in it helps. (I bottom-water all my seedlings with Bt-infused water too.)

Here are the directions that are on the package of Begonia tubers that I bought at the hardware store. I usually fill the pots loosely with moistened soil, then push the tuber down into it, and cover the tuber with a thin layer of more soil.

The directions (beside the big number 2) describe a "knobby side" and a "round side."

Here's what the round side looks like -- I think of it as covered in old roots

Here's the knobby side -- it's where the stalks and leaves of the new plant will arise (the white flakes are wood shavings)

Empty pot about the size of a black plastic nursery gallon, which will hold one of the Begonia tubers

Two filled pots, one tuber in each pot -- actually crocks from the thrift store, so they lack drainage -- which means I'll have to be careful about watering next summer. But they like water, and I hate watering, so things should balance out

The rest have been potted up into four-inch plastic nursery pots, to await sprouting.

Unfortunately, there's no room for the Begonias on the shelves with heated mats, because they are full to bursting with seedlings. That's another post.