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Last updated January 22, 2008

About Badgersett Hybrid Chestnuts

Chestnut Blight and Badgersett Hybrid Chestnuts

We do not have the chestnut blight here at Badgersett, so we cannot test our trees here. However, years ago, comprehensive samples of our materials were sent to both China and Auburn University, in Alabama- blight is a fact of life in both places. Dr. Huang Hong-Wen conducted extensive observations on our chestnuts in both locations (his results were published in Root & Branch #4). Basically, he found about 80% of our seedlings to be functionally resistant to the blight, with about 20% succumbing to the disease. That is actually better than we had hoped for hybrids of this sort. While it cannot be a guarantee of resistance, it is an excellent indication.

Where will they grow?

You get into heated arguments on this one. There isn't a definite answer except that quite a lot of what people know is not true. A basic consideration in answering this question is what species you are dealing with. The different species are in fact just that: different. The fact that they can be crossed genetically does not mean they are similar in their environmental requirements.

Cold hardiness: Virtually all of the Chinese chestnut in this country is of sub-tropical or warm, wet, oceanic temperate origin, and will suffer from periodic cold damage anywhere north of Zone 5. If you can't grow peaches, don't try Chinese chestnut. Japanese is typically hardy to zone 6, European to zone 5. American chestnut is more confusing, and it does depend on the origin of the seed. Some Americans grow well into zone 4, even edging into 3, but not all. I've grown some pure American chestnut from northeastern Ohio, near Lake Erie, that was less cold hardy than common Chinese. The hybrids we sell are guaranteed to be the most cold hardy chestnuts on the market anywhere. They are absolutely cold hardy in Zone 5 and warmer, and suitable for trial in Zone 4.

We do have subtropical genes in our mix of genetics, but since we have pushed towards cold adaptation it is likely that these plants will have a higher failure rate starting in zones 8-9 and above. We have had successful plantings in Auburn, AL and Wuhan, China, but we do not have good data on whether the initial seedling failure rate was higher there than in climates closer to our own.

Soils: I've seen mature pure American chestnuts growing quite happily in pure sand, nearly pure clay, on mountain tops in granite gravel, and in black muck in a swamp 5 inches from skunk cabbage, with buttresses. In China, I've seen chestnuts grow well in wet tropical laterites, besides the more normal soils. Traditionally, people believe sandy soils are better, but I'm not sure this is anything more than looking at where wild trees are most often found, which doesn't mean much in cultured situations. At Badgersett, we have a deep loess soil (silt loam); pH about 6.5 usually, drifting down to 5.5. Wild chestnut forests are not found on limestone derived soils, but chestnuts will grow in limestone areas if provided with extra nitrogen in the fertilizer.

Rainfall: Historically, chestnut forests around the world are seldom found where rainfall is less than 40" per year, but irrigation can certainly serve in lieu of rain. At Badgersett, our average annual rainfall is about 28". We do not irrigate, but we have a deep soil with good subsurface moisture retention. In extreme drought years, we've had a few trees die, but only a few.

Problems with Hybrid Chestnuts

Unlike the hazel hybrids, which have basically "restabilized" genetically after the cross between species, hybrid chestnuts have not yet restabilized. Seedlings can be quite variable; the best are excellent, but some of them will be weak.

One particular problem in northern areas is a trunk infection from fungi not normally a problem to chestnuts. Apparently, the south side of the trunk can be injured in winter when the sun shines on the trunk on a cold day. The surface of the trunk warms up considerably, and then the sun goes behind a cloud. The warm trunk quickly freezes, and injury results. Some of these hybrids appear to get infected this way, leaving the trunk weak. The problem decreases the farther south they are planted, and we are working to increase the number of trees that do not have the problem. Right now, though, in our area and north of here the problem is real.

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