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Hemlocks and HWA (9 Replies)

Posted August 1, 2013 at 10:31 am

I’m Z5a in the northeast with a lot of shade so Tsuga canadensis is a favorite almost by default but the specter of Hemlock Woolly Adegid hovers over every collecting impulse I have. Nurseries here in Maine and neighboring NH aren’t allowed to bring in any cultivars that aren’t home grown and inspected by the state. Thus, we don’t have much variety available. Anybody have any suggestions as to how I can feed my craving without ending up in the slammer? I’m dying for a shot at Tsuga canadensis ‘Albo-spica.’

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Posted August 27, 2013 at 8:38 pm

Sean,
Have you ever visited Carol’s Collectibles near Belfast? (http://www.carolscollectibles.com). She doesn’t have the plant you are lusting after, but does have some nice hemlocks that she has grown for a number of years. I bought a Jeddeloh there a few years ago and am very happy with it.

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Posted August 27, 2013 at 9:34 pm

Hi Wynne. Yes, I know Carol from when he was in CT and a rhody maven. She was also close to Sid Waxman and had a lot of scion wood from him that she was propagating. (I’m also a collector of Waxmans.) And I got some Tsuga from her back then.

I’ve been meaning to get over to her place since she relocated but haven’t found the time. Thanks for reminding me. I do go to Belfast regularly since that’s home for Pica Design (going tomorrow AM, in fact) but this past year, building the new site has left little time for planting so I’m reluctant to have pots lying around that I can’t find a good home for. As you know, wintering over is a challenge in these here parts. Maybe next spring I’ll make the reacquaintance with Carol.

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Posted February 7, 2014 at 1:12 pm

I noticed Sean referred to a albospicata. How does that differ from the gentche white hemlock? They look very similar. I too collect a few tsuga but the deer don’t want me to have them for very long.

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Posted February 7, 2014 at 2:06 pm

Although there are many references stating that both cultivars are upright, rounded dwarf pyramids that attain approximate equal size at maturity, that’s not been my observation from the specimens I’ve seen.

My 10-foot ‘Gentsch’ more typically conforms to that description whereas the ‘Albo-spica’ I’ve seen elsewhere are wider, more open and of intermediate classification. (See the photos in the link to that conifer record that I posted above.) ‘Albo-spicata’ has longer, more concentrated new shoots of white in the spring whereas ‘Gentsch’ sports creamy white that is mainly at the very tips and shows best in the fall. ‘Albo-spicata’ also seems to grow faster than ‘Gentsch.’

Otto Gentsch, a West Merrick, Long Island, nurseryman introduced it to the trade in the 1960s but ‘Albo-spicata’s first published mention goes back to 1866.

I had a deer problem with tsuga cultivars in my NH garden, located at a summer home, where the plantings are on their own for 6-8 months of the year. Some years after establishing the collection I began to have serious deer predation during difficult winters. I was flummoxed by the fact that deer would walk through miles of native hemlock to turn my tidy collection of rare cultivars into their salad bar.

Finally, at an ACS regional meeting I met a forester who listened sympathetically to my tale of woe and asked if I fertilized. “Yes,” I said knowingly, “in early spring to push new growth and then again in August to give them a booster shot to last them to dormancy.” “That’s your problem,” he said. “Amino acids. Your hemlock has more of it and they can smell it. They know it has more nutrients.”

So I’ve stopped with the booster shot. My hemlocks grow slower but the collection no longer looks like a war zone.

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Posted February 8, 2014 at 4:15 pm

The ‘Albos’ I’ve seen are as you’ve seen them, Sean. Stouter and longer white tips. The forester was spot on about ferts as well. More nitrogen means more sugars and a tastier plant for both animals and insects. This is true of most all plants.

As for HWA, I read in a Northern Wisconsin newspaper that HWAs pretty much die off with temps of -5F. They did not list their source, but if true, this past winter should do a number on them throughout their northern range.

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Posted February 9, 2014 at 2:49 pm

My gentsch and others were heavily damaged by deer and cold last winter but have bounced back this year (so far) Good news about the low temp effects on HWA should it get this far. I ran into a pest called” Pale winged grey ” in Nova Scotia a few years ago . It can completely destroy old growth hemlock stands in 1 to 2 years and it starts with the regen and works its way up the tree. Last I heard the population had collapsed. Any experience with that in the US Northeast? I haven’t heard of it in NB yet?

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Posted February 9, 2014 at 9:11 pm

If the winter is severe, starving deer will eat anything. My experience has been that even the thorniest of hollies won’t deter them.

As you probably know, the Pale-winged Gray moth (Iridopsis ephyraria) is native to the Canadian maritimes (but ranges as far west as Alberta.) The Kejimkujik National Park in NS has been hard hit.
We have seen some evidence of it in the Kennebec valley north of me but it’s not on Maine’s Dept. of Forestry’s watch list. The Pale Gray’s egg laying habits affect deciduous trees as well but the hemlock appears to be most severely affected. There is no known control for it or why it seems to be blooming now after being part of the ecosystem for generations.

In our parts, for conifer lovers, HWA is our big concern. We’re seeing it gradually spread up the Maine coast, probably via migratory shore birds. The good news is that it is not spreading too far inland where it starts to turn to Zone 4 and 3. Tom is reporting similar results in northern Wisconsin. Our cold winters may be slowing it down but that’s little consolation to other NER Tsuga aficionados, especially in the lower Appalachians. What adelgid has done to the Blue Ridge landscape is tragic.

Conifer collectors in much of the eastern US have given up on T. canadensis. Many states prohibit nurseries from importing it — it entered the US in Richmond, Virginia, about 1950 on nursery stock from Japan — so finding interesting cultivars is extremely difficult.

If it shows up in your neighborhood, state or local authorities may start clearing and they will look at your collection skeptically. If it shows up in your garden and you spot it quick enough, HWA can be treated with horticultural oils or synthetic sprays but if it’s in a surrounding woodlot be prepared to fight a never-ending battle.

There has been some success in treating it with a predator ladybug beetle that Dr. Mark McClure discovered in Japan. McClure, when heading up the CT Agricultural Experimental Station in the 1990s, lead much of the research on finding a biological control for HWA. Since his retirement others are carrying on this important work and have found other predators. But it’s ridiculously expensive to breed these insects for release, funding has shrunk and the best we can hope for is to moderate the spread of HWA. Unfortunately it will always be with us.
Tsuga canadensis photographed in Dave Olszyk's Glacier's End Arboretum in Lacy, WA, during an ACS garden tour.Of course there are Western and Asian Tsuga species that are more resistant to HWA but, to my mind, there aren’t yet that many interesting cultivars that can match the graceful sweep of T. canadensis and ‘Albo-spicata’ in particular. (Photographed in Dave Olszyk’s Glacier’s End Arboretum in Lacy, WA, during an ACS garden tour.)

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Posted February 10, 2014 at 5:47 am

That’s very interesting and encouraging. last I heard the PWG in Kedji Park NS population and others in that area had declined? Maybe I’m too cold here in NB (5a) . As to the Albo spicata do they require full shade or part shade and high fertility for their best show?

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Posted February 10, 2014 at 7:27 am

The PWG moth may be in decline in Nova Scotia; the study I read was a few years old. Albo-spicata hemlock, like other white foliage plants, can’t take too much sun because of its limited chlorophyl in all those white shoots. It is subject to burning so PM shade is recommended. Dave’s gorgeous specimen (above) is in such an ideal spot, not the least because he’s in the cloudy and moist Pacific Northwest. As mentioned here, goosing them with fertilizer, particularly later in the season, has its downside if your garden is prone to deer predation.

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