Planting depth for tuberous begonias

Hello all,

I grew up with begonias - but with begonias in Alaska, where you can pretty much grow them in full sun because even then it's always cool, by stateside standards. They were everywhere around the yard, and beloved for their constant color. Throughout my childhood one of the sure items on the daily summer Kids' Chore List was watering the (30-50) begonia pots. With a watering can.

I live on a lake in western Minnesota now - colder than Home, but the growing season is certainly longer, and at least in a normal year, it's warmer. (It's been a while since we had a normal year, unfortunately.) In remembrance of Mom and Home, last year I brought home a few Non-Stop begonias from the nursery where I work in the summer, and they were a daily pleasure in my part-shade area near the lake. I didn't let the pots freeze in the fall, but brought them into the garage, where I let them dry out and eventually sort of disappear. They're still in those pots. But danged if I can find the tubers!

Mom grew her fabulous begonias with the tubers set about 2/3 to 3/4 into the soil, the soil itself never being allowed to cover the bulb. These Non-Stops I brought home - well, if they're still there, they're underground, and they're *small*. I've been looking around for advice about growing tuberous begonias in "the States," as we used to call the Lower 48 when I was a kid. Many sites advise about 1/2" of light soil (which I take to mean the commonly recommended peat and/or perlite mix) covering the tuber. I think this is what the grower of my Non-Stops did.

Mom would never have allowed this! Moreover, she told us to make sure *never* to get water on the center of the tuber, when we were watering. But then, she was growing another kind of begonia - the enormous 4-6" flower kinds. So maybe it was different?

So, my question is, if you bury your tubers in that 1/2" of soil, exactly what kind of mix do you use, and what are your watering practices, and what kind of weather do your plants have to endure, that make your routine work? Considering Mom's practice - bagged potting soil (but real soil) with a fairly high proportion of peat and perlite, lots of light (long Alaskan summer days) but not a lot of heat - can you see where her planting method (very much on the soil surface) and watering instructions to us made sense?

I am reluctant to bury a bunch of fairly expensive tubers under even 1/2" of soil, when I've never seen success from that method. But then this year will be the first time I've ever started from bare tubers here in Minnesota. I *did* lose one tuber to rot on the plants I brought home last summer, and wonder if it wouldn't have been better off if it hadn't been buried. (I didn't choose the soil depth for that one - it was just the way the grower potted it, and I moved it into a bigger planter at an identical depth.)

So, dear begonia gardening friends, have at it: what successes and failures have you had with the big-flowered tuberous begonias, either upright or trailing, under what conditions? Add to my understanding and ability to interpret what I see when, this coming summer, I honor my mother's memory and cherish one of the delights of my childhood. Thanks in advance --

Joan

I would use just a light covering of vermiculite ,but leaving the top bare is okay too----as long as no water gets there. You might try sprouting them first by just pressing the tubers into a layer of moist vermiculite.

Is the purpose of covering the tuber with vermiculite the maintenance of humidity over the upper surface? That would make sense to me.

Then, when you transfer the sprouted tuber to its growing medium for the season, would you just shake that off and leave the tuber open to the air on top?

Yes, and yes.
Just barely cover and don't get water in the tops.

Sounds good, thanks!