Q: I planted 'Dragon Begonias' this year on the advice of a friend after complaining that NOTHING would flower in my shady yard. I bought a dozen plants mail order, put them in the ground in early spring and by Mother's day, all but one were thriving. My husband bought me another four plants at a local nursery and I planted them in the same area. It is now near the end of August and my begonias have thrived, providing me with a beautiful bounty of non-stop lovely red blooms that delight me every day. My question is: Can I somehow preserve them for replanting next year? I've been asking friends and I've gotten as many answers as I have friends. Some say, "no way; when they die, they're done". Some say to cut them way back at the end of the season and bring them indoors in pots. Some say to hang them bare root in my basement thru the winter. What do you say??"
- ----Rose in Riverton, New Jersey
A. Well, she certainly asked the right person! Or maybe somebody finally me asked the right question…or…
Anyway, I've been personally perennializing my begonias for many years and can say from experience that it is super easy. But before we get into the details, we should mention that there are two distinctly different types of begonias.
Actually, there are 1600. But that's species; we're talking about the two main types here. Her "Dragonwing" begonias—a popular line of hybrids with big leaves and very colorful flowers—are an example of the 'bedding plant' type, sold as seeds or small plants and meant to be displayed in shady gardens from Spring until Fall, when the first frost kills them—same as other ' annuals' like marigolds and impatiens.
The other type are Tuberous begonias. These fall into the category of ' summer blooming bulbs'. Like dahlias, tuberous begonias are sold as big bulbs or rhizomes (the 'tubers'), and are typically planted in containers, so that you can easily take the root out before the first hard frost and store it indoors for the winter.
Now yes, some of you can just plant it in the ground and mulch it heavily, but only those of you in very warm climates. Tuberous begonias and dahlias are very frost sensitive, and in most (as in 'almost all') parts of the country you must bring the 'roots' inside over winter.
One way to do this is to just bring the whole pot inside. If you can provide bright enough light (really bright light; more than you'll get from a so-called 'sunny windowsill'), they'll bloom indoors all winter. If you can't provide that light (either via artificial light or a solarium kind of set-up) put the pot in a cool dry place in the dark and let the bulb go dormant—although most experts would say it's better to remove the bare roots, pack them in slightly damp perlite and peat moss and store them in a cool dry area, safe from mice.
But we're not talking about tuberous begonias here! (At least we weren't planning to.) We're talking about the so-called 'annual' bedding plant begonias—which are actually perennial in frost-free climates. Which in 97.6 of the US means indoors. Pot them up and bring them inside before the nights start dropping into the 40s, and they'll bloom for you all winter long.
And here's the best part: Unlike their tuberous cousins, annual begonias don't require a lot of light. These are shade-loving plants outdoors; so any somewhat-sunny windowsill will keep them alive and flowering—just make sure it's well insulated so they don't get too cold at night.
The friend who recommended cutting them back before bringing them in? That's utter nonsense. I've never done it, and some of my 'annual' begonias are over a decade old. And hanging them upside down in a garage? Why do that when you can keep them alive, blooming and cheering you up all winter? ("Forget about the ice dams on the roof, honey—look at these begonias!")
Just assemble a bunch of containers with good drainage holes and fill them with a mixture of compost and good quality potting soil—that means a very lightweight bag of 'soil-free' mix with no added chemical plant food (natural, gentle foods like worm castings are fine), water holding crystals or other nonsense.
Do this NOW; don't wait. Then you can leave the planted containers outside in the shade, water them really well and bring them indoors a week or so later, when they'll be over any transplant shock and the nights won't have gotten too cool.
Let me emphasize one super-important point here: People should NOT use garden soil in any containers; potted plants want a combination of compost for nutrition and a nice light soil-free potting mix for good drainage. Of course, you can keep some of your garden soil around the roots when you transplant them—but that's it. If you fill the containers with outdoor dirt, you'll have sickly looking plants instead of beautiful indoor color.
I repeat: Buying soil-free mix is NOT an extravagance—in fact, it's one of the few things I personally buy for my own plants, and I buy fresh bags every season. I would never fill a container with anything but compost and a high-quality potting soil (aka soil-free mix, seed-starting mix, etc.). And I have excellent garden soil. Got it? Good!
OK—so you have your begonias properly contained. Then water them by sitting each container in a sink, bucket, wheelbarrow, trough or bathtub filled with a few inches of water for a half hour. When you lift the containers out to let them drain, note how heavy they feel. Don't water them again until they feel much lighter. And don't let water collect in the saucer underneath the pot. Those saucers are only there to protect surfaces under the plant. Water too often or let the plants sit in standing water and you'll get root rot and fungus gnats.
And don't rush the season when (you think) it's time to take them back outside for the summer! April is much too early, and our listener is lucky she didn't lose her baby begonias to frost—or make them sickly from exposure to frigid nights. As with tomatoes, these tropical plants do best when they don't go outside until nights are reliably in the 50s.