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Sequoiadendron ‘Hazel Smith’ and USDA Zones (11 Replies)

Posted May 22, 2018 at 1:58 pm

Group,
I was wondering if anyone might be able to clue me in concerning the logic of “hardiness zones”. Most giant sequoias (Sequoiadendron giganteum) are listed as hardy to USDA Zone 6. However, the description for Sequoiadendron ‘Hazel Smith’ provided on our website states that it is known for its cold hardiness. And yet our website STILL lists this cultivar as hardy to only zone 6. How is that?

What puzzles me still further is the fact that the USDA lists my area (near Elkhart, Indiana) as borderline between zones 5 and 6 giving us the lowest temperatures of around -10°F. I find that also highly puzzling since I have seen it get much, much colder than that here.

Looking through numerous websites on “Hazel Smith”, some state it’s hardy to zone 6 and some to zone 5. So, which is it? One well-known nursery in California states that regular, Plain-Jane Sequoias grow in “all zones” which I have discovered is just plain not true.

Can anyone on our list shed any light on hardiness zones?

Regards,
Fred M. Cain,
Topeka, IN

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Posted May 22, 2018 at 5:36 pm

Hi Fred … Cold hardiness is by no means an exact science. So many factors are involved, i.e.

♦ absolute cold temperatures reached
♦ how cold for how long
♦ when in the season it gets really cold (this part’s really important)

People who are well versed in “zone pushing” or “zonal denial” know precisely where in their landscape the cold- and warm-pockets are and plant accordingly. You appear to be in a “cold pocket.” Given the recent spate of polar vortices settling over the U.S. midwest over the past few seasons, everything that may have historically been true may no longer be necessarily so. By my observation, the Pacific NW well into Alaska is getting warmer, while the midwest and northeast are cooling down.

When growing plants, I’ve always found it helpful to know their native climates. In the case of Sequoiadendron giganteum, it’s native to the high Sierra Mountains of California, meaning very cold and snowy in winter; and bone-dry & hot in summer. Plants are adapted to receiving little to no water in summer (excepting an occasional thunderstorm), with relative humidity of well under 50%. I say this only because climates other than which they’ve adapted will result in reduced vigor, making the plant more at risk for being taken out during an exceptional winter.

In Sequoia National Park in California, the average daytime/nighttime winter temperatures are very consistently between 35 to 15ºF (1.5 to -10ºC), making USDA Zone 8 the “sweet spot” for this species. Clearly it’s hardier; there are places within its native range that are much colder.

Even in my USDA Zone 8a in Washington state, I can tell that my Sequoiadendrons aren’t particularly happy with our long wet springs. They tend to look a little “off” until the rainy season is past. Happily, by mid-summer they get over themselves and look amazing.

Your remark about California at the end of your note made me chuckle. 95% of California is between USDA Zones 8 and 10 with only the very highest mountains in Zones 6 and 7 (looks like Mt. Whitney may very well be Zone 5, but that’s well above the tree zone). So when a California nursery is saying all zones, they’re actually saying USDA Zones 8 to 10.

One final fly in the ointment is that the USDA developed this whole conundrum of climate zones for the agricultural industry — food crops not ornamental gardening. In order to get an idea of what will grow in your particular part of the country, looking around is necessary. If you don’t see it growing in your surroundings, it probably won’t work for any number of reasons. In my own experience, I have issues with Abies veitchii; it’s plenty hardy; it just doesn’t like my modified Mediterranean climate: too dry in summer. That makes sense, because this species is native to the mountains of Japan — very humid with lots of summer rain.

sorry for my rambling response, I hope it brings light to a oft-times frustrating process.

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Posted May 22, 2018 at 6:10 pm

Is there going to be a quiz?

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Posted May 23, 2018 at 7:10 am

Dear “Conifer Editor”,

Thanks so much for your response and information. What you are saying seems to make sense. I especially liked the part of your response where you said that “the USDA developed this whole conundrum of climate zones for the agricultural industry — food crops not ornamental gardening.” Yes, that makes sense.

Now I can offer you a bit of info that helped me with my Sequoias: You mentioned that yours get sick-looking during the long rainy season. If you get a few days in there where the rain lets up a bit, try spraying them with a systemic fungicide. That really helped me a lot. You see, apart from the hard winters in Indiana we also tend to have very warm, damp summers. “Juniper rust” is only a minor blemish on most junipers but I learned the hard way that it is often fatal to a Sequoia. As you mentioned in your post, the growing season in the Sierra tends to be dry with low humidity. Don’t know if you have a similar problem or not but you might try it.

Regards,
Fred M. Cain

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Posted May 23, 2018 at 1:18 pm

Hi Fred … I’m strongly against applying synthetic chemicals of any form to my landscape. The animals that transit the property and micro-flora/fauna in the soil are far too important to me. Plus my largest Sequoiadendron is about 50 feet tall. It would require a fortune’s worth of systemic fungicide to inoculate that.

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Posted May 23, 2018 at 1:25 pm

Dear “Conifer Editor”,

Wow ! 50 feet tall? I’d say that if fungus or Mother Nature has let that get that big by now then you probably have little to worry about. I don’t have any objection to using chemicals, myself, if they work. But your admonishment has now made me think that I should probably read the label again and see what the active ingredient is then do some research on it.

Regards,
Fred M. Cain

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Posted May 23, 2018 at 4:25 pm

It’s always good to learn, Fred. Might I recommend starting your research with the article at this link describing the wonders of mycorrhizal fungi. A systemic fungicide doesn’t know a good fungus from the bad. It kills everything.

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Posted May 24, 2018 at 7:31 am

Dear “Conifer Editor”,

I have wondered before about mycorrhizal. I should probably get some of that since I know that it promotes strong root development.
However, the fungus that I have an issue with is above ground in the needles. What I encounter are tiny little brown specks that appear on the needles during mid to late growing season. In a year’s time the speckles appear to expand into a canker that eventually girdles the branchlets. I actually lost a couple of vigorous Sequoia saplings before I found out what was wrong.

I found out from a guy in Alabama who was trying to grow Sequoias down there. He told me that this particular fungus is destroyed by ultra violet (UV) radiation in sunlight and that if you lie above around 2,500 – 3,000 feet above sea level, the UV levels are high enough to kill the fungus. But at lower elevations the UV radiation might not be strong enough to do its job. I am around 500 feet here.
This same guy from Alabama told me to try a systemic fungicide. I did and had great success so I kept using it (until two brutal winters killed my trees anyways).

I believe what I’m using is “Propiconazole”. I “Googled” for it and all I could find is that it’s dangerous for aquatic life. There are no streams or ditches near our property and I only spray in dry weather so I oughta be O.K. there. And yet, still, if I could find a “greener” or organic method to keep this fungus under control – that’d be GREAT !

Regards,
Fred M. Cain,
Topeka, Indiana

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Posted June 1, 2018 at 8:07 pm

I tried to grow ‘Hazel Smith’ for years, in Zone 5, northwestern Pennsylvania, probably very similar to Elkhart. About every third year it would get severe winter burn, would survive, but I had to prune off lower branches. It never looked nice. Finally after about 9 years, it died completely. Every 5 to 10 years, the arctic express will take it down to -17 or so, and unfortunately I don’t think any Sequoiadendron can take it. Incidentally, ‘Hazel Smith’ was developed at Watnong nursery in Connecticut, which is Zone 6, also much more humid summers than the West. The original tree is still growing there, though it is now a city park rather than a nursery. Dawes arboretum, near Columbus, Ohio, borderline between 5 and 6 depending on which map you look at, has a nice specimen.

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Posted June 4, 2018 at 7:34 am

Wdunagin,
Uh-oh. Your report doesn’t sound too encouraging, I’m afraid. You stated that your Hazel Smiths froze out at about -17°F? What the heck? That is just about the same temps that my plain-Jane Sequoias froze out at that were not billed as cold hardy! It seemed to me they could go down to -10°F O.K. but below that they were toast. That is about the same temperature range that peach blossoms freeze out at.

Now I’ve started four Hazel Smiths so you’ve got me to wondering if they might not make it after all. I have read that the highest grove of Sequoias in the Sierra Nevada mountains is thriving at an elevation of nearly 9,000 feet. That’s pretty high. At that high elevation, winter temperatures could easily reach -20 to -25­°F. But the thing is that the -25° in the Sierras is not the same as a -25° reading east of the Mississippi. The difference is in the wind. A reading that cold in California would occur on a very cold, dry night with no wind. A reading of even a -10F in Indiana or N.W. PA might be packing a 35MPH wind accompanying the so-called “arctic express” that you mentioned. We’ll see.

They have recently upgraded the hardiness zones in our area due to “global warming” and “climate change”. Guess what? The testimony from the Sequoias tends to suggest that that’s not happening. Maybe scientists should take a clue. Has the climate in the U.S. REALLY changed in the last 50 years? Maybe so but I’m not seeing that.

The Idaho Endurance strain was reported to survive several nights of -40F° in the 1960s. However, once again, that’s not the same -40° as it would be if it occurred in Indiana or PA. Another puzzlement is that in spite of those bitter cold temps in the ’60s, the USDA rates the University of Idaho as lying in between zones 6 and 7! So, that seems kinda strange to me.

In any event, I think I may have found a source for Idaho Endurance so I might try that next.
Regards,
Fred M. Cain,
Topeka, IN

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