Saturday, November 1, 2014
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.
Begonia sizemoreae in the garden (October 2010)
Begonia sizemoreae hybrids (B. grandis × B. sizemoreae)
Begonia sizemoreae is an extremely variable species, and there's some question as to whether more than one collection or clone is in cultivation. Perhaps some of this variation has emerged in seed-grown plants, uncovering hidden genetic heterozygosity. But there's another explanation: culture. This was brought home to me rather dramatically when I looked at photos of the same plant taken at different times during the year. Compare this photo from the summer:
Begonia sizemoreae (early July 2011)
with this photo of the same plant, taken in early December after a long period of cool temperatures:
Begonia sizemoreae (10 December 2011)
It's hard to believe this is the same plant. Not only is the color different, but the intensity and contrast of the pattern as well. I've discovered that many other begonias can vary quite a bit depending on cultural conditions, and in this case it's probably temperature-related.
Our first hard freeze came unusually late that year. Many begonias are fairly cold-tolerant and will look good right up until frost, but once it freezes, they're done in a dramatic way. Here's the plant the very next morning, after a hard freeze of 29 degrees (F); it collapsed in a pile of mush as soon as it thawed:
Begonia sizemoreae (11 December 2011, at 29 degrees F)
Even so, not all the leaves froze; I was impressed that the concrete steps and wall apparently radiated enough heat to keep some of the leaves from freezing. The plant actually survived this freeze with no damage to its rhizome, but shortly after this I gave up on the species to make room for some of the hardier ones that I'll be writing about in my next blog post!