Thursday, December 12, 2013
The begonia that broke my heart
Unnamed begonia hybrid, a heartbreaking beauty (June 2012)
I hope to (eventually) blog about some of my successes with begonia breeding, but for now I'm going to describe one of my failures. The plant in the above photo is one of my own hybrids, photographed in my garden in June 2012, from a cross I made in 2011. I call it a "beautiful failure" because it ultimately failed several critical tests, and as of 2013 I'm no longer growing it at all.
The seed parent of this hybrid was Begonia grandis. Begonia grandis is commonly known as the "hardy begonia"; its primary claim to fame is hardiness, but as begonias go, it's rather drab. I've been crossing this species with numerous other begonias in an attempt to get its hardiness into hybrids with more interesting foliage.
Begonia grandis 'Early Bird', an early-blooming selection of the species
The pollen parent was Begonia U489. This is a plant of somewhat mysterious origin, known only from cultivation. The "U" designation refers to a numbering system used for unidentified begonias by the American Begonia Society. U489 supposedly comes from Vietnam, but was probably purchased in a market. It is not any species that I can identify and seems to be a rex hybrid; its large, silvery sea-green leaves with a small deep green splotch in the center are very distinctive. Most promising for my purposes is that it is fairly hardy, and has survived two (mild) winters in my own garden with only a light mulch for protection.
I made the cross in summer 2011, sowing the seeds that fall and growing the seedlings under fluorescent lights over the winter. The first hint that I might have something interesting came when some of the seedlings began to show distinct silvery markings at a very early age. This also told me that I hadn't accidentally self-pollinated B. grandis. As they grew and more of the seedlings started to show interesting leaf patterns, I became more and more anxious to see the hybrids grow to maturity. Plant breeding is a rather odd hobby for somebody with as little patience as I have!
Seedling of B. grandis × U489 showing its first markings
Seedlings of B. grandis × U489
I ended up with a huge amount of variation from this cross, a strong indication that U489 is probably a hybrid rather than a species, which would produce a more uniform F1 generation. Out of several hundred tiny seedlings that I screened for interesting leaf markings, I eventually saved and grew on about two dozen of the best. The leaf patterns fell into two broad types: one group with a broad silvery margin and central green splotch, somewhat like U489, and the other group with silver speckles and splotches quite unlike U489. I planted the seedlings in my garden in early May, and as they grew they just kept getting better and better. By June I was convinced I had some real winners on my hands. One seedling in particular stood out for its large leaves and bold pattern.
B. grandis × U489 seedlings in the garden (May 2012)
B. grandis × U489 seedlings in the garden (May 2012)
B. grandis × U489 seedlings in the garden (June 2012)
And then came July. Washington, DC had a record-breaking heat wave in 2012 with an extended period in the high 90's and several days in the low 100's. This was simply too much for many of my begonias. The seedlings from this cross didn't melt outright as some of my other begonias did, but after the heat wave they looked terrible. I might have forgiven that, except that they didn't put out much new growth after that; the initial flush of gorgeous spring foliage seemed to be all they had in them. I've discovered this problem with several of my B. grandis hybrids: they put out beautiful foliage in the spring, but stop producing new growth by mid-summer. Without new foliage to replace it, the old foliage looks increasingly tired and tattered as summer wears on.
Even then, I might have forgiven this one delectable seedling its faults, but it still had one last test: winter. When fall and freezing temperatures came I left all the seedlings from this cross in the ground, mulched them, and crossed my fingers. This is the test all my begonias get, because I want to identify the hardiest plants to breed with, and don't want to produce beautiful delicacies that need to be coddled! I'd already had surprisingly good results from another cross so I thought my chances were pretty good with this one.
This spring I anxiously waited for my various begonias to emerge. Many of them did, including species and hybrids that I hadn't expected to survive, certainly helped by a warmer-than-average winter. Finally, I saw growth emerging from one of the B. grandis × U489 seedlings. Then another, and another. In total, about half of them had survived... but the best seedling, the one I started this blog post lamenting, wasn't among them. I waited all summer, hoping it would eventually re-emerge from some little bit of rhizome left alive underground, but it was gone. After insufficient heat tolerance, and failure to produce new growth after early summer, lack of hardiness was the third strike and it was out!
The next-best seedling from the same cross likewise didn't survive, but had had the same issues. I allowed the surviving siblings to grow again this year, but although they held up better through a more typical Washington, DC summer their foliage isn't nearly as nice as the ones I lost and none of them are as vigorous as I would like. These seedlings are now going into their second winter but I probably won't name or release any of them, unless one of them not only survives another winter but really impresses me next year.
B. grandis × U489, surviving seedlings in September 2013
Although my long-term goal is to breed hardy begonias, with many of my crosses I'm finding lack of heat tolerance and poor summer performance to be the bigger issue in the short term. Many gardeners are willing to grow a plant for a single season as long as it grows well and looks nice--this is the basis of our entire annual plant industry! But no matter how beautiful, if it collapses or looks tired in the summer, it's just not worth growing, even if it's likely to survive the winter.