Hardy begonias: the next generation

In a previous post (Beyond Begonia grandis: new hardy begonias), I discussed several begonia species and hybrids that have been around for a few years and were already known (or purported) to be fairly hardy.  In this post, I'll discuss a new generation of begonias I've discovered to be hardy in my zone 7a/b garden in just the last few years, even though some of them have been around much longer than that!

The mystery maidenhair fern

Adiantum sp., still green after 20° F

Winter has come a bit early this year, with a low temperature of 20° F (-6.6° C) a few nights ago, and several more nights in the low 20's.  It's very unusual to have temperatures this cold before mid-December.  Yet among all the brown and crispy frozen foliage, one bit of bright green still stands out: a maidenhair fern (Adiantum sp.).

Garden bloggers bloom day: November 2014

Despite a few evening clouds, it was cold and clear last night in Washington, DC and we finally got our first good freeze of the season.  I've had a couple of very light frosts already, when overnight lows were in the 30's, but without any damage to my plants.  Last night was the first time it went down to the freezing point, 32 degrees F (0 C), or perhaps slightly lower.  When I went out this morning to survey the damage the first thing I noticed was the sickly sweet smell of frostbitten vegetation.  That's the part I always forget.

Beyond Begonia grandis: new hardy begonias

Begonia grandis, white-flowered form

Many gardeners are familiar with Begonia grandis (a.k.a. B. discolor, B. evansiana, B. sinensis), a tuberous species from China commonly known as the "hardy begonia".  The name is well-earned: this truly is the hardiest species in a huge but mostly tropical and subtropical genus, going dormant in the winter and able to survive freezing temperatures into zone 6.  But for a very long time, the most exciting news about hardy begonias was that they came in white as well as pink.  In a genus with so many flashy plants, neither the foliage nor the flowers of B. grandis are terribly exciting.  The leaves are handsome enough, and the pink or white flowers are nice coming so late in the season... and darn it, it's a hardy begonia.  But hardiness is mostly what it has going for it, and is offset by the thing being downright weedy.  It produces little aerial bulbils that act like seeds, dropping all over to produce a steadily-growing colony that will eventually crowd out smaller and slower-growing plants.

Hooray for the urban heat island

Begonias, in for the evening

Last night, I piled some of my begonias into a plant tray and brought them indoors for safekeeping.  There was a forecast of near-freezing temperatures and near-certainty of frost, but this time of year I always gamble a bit, bringing in just my most tender or irreplaceable plants, and leaving the rest to their fates.  We may be well into November but I'm not quite ready yet for the annual routine of lugging potted plants in, and putting sheets over the plants I can't bring in, every time a frost is predicted.  It's just too damn much work (have I mentioned before how lazy I am?).

Begonias and temperature

Begonia sizemoreae (female flowers)

With temperatures dropping and the growing season coming to an end, I was going through some old photos for a blog post I'm putting together and came across some photos of a plant I no longer grow, Begonia sizemoreae.  This recently described species from northern Vietnam is closely related to B. rex (and according to some botanists the two belong to the same species).  I picked up this plant on a whim at a local begonia society show and grew it for a few years; while it didn't turn out to be the least bit hardy, it did give me some interesting hybrids that survived a couple of warm winters in the ground and encouraged me to attempt more crosses.