I’m setting up a spot on our property here for field growing, I’m zone 5b. I’ve got a few landscape-size deshojo and shishigashira that I’m gonna put in. They’re on big ugly grafted rootstock–really only useful as parent plants for layers.
So, do any of y’all know how cold durable deshojo and shishigashira’s native roots are? I’d assume they’re fine to at least 28°f obvi…but that’s not gonna cut it for chilly 5b!
I’d love to take layers and pop those in the ground, but not if it’s gonna smoke em over the winter…the primary reason why I scooped up a few of these two varieties, is because they’re pretty hard to find around here and I’d love to start getting more of them out to the community.
Tangentially, what else do y’all think I should put in? Things I have that are destined for the field: a few kishu, dawn redwood, amur maple, larch, probably a thing or two I’m forgetting…
I don’t have any data, but you might try a polytunnel with or without a heat bed set to keep the roots warmer. Bonsai Heresy lists 15F (-10C) as the root kill temp for Acer palmatum (no cultivar listed). Even a polytunnel can make a big difference since it conserves some of the heat coming from the ground.
Nice, thanks @MartyWeiser!! I asked a whole bunch of horticulture pals with no solid answers (I have a pretty solid horticulture background too, but couldn’t find a good answer anywhere)…should’ve just started here first
5b minimum avg temp is as low as -15f soooo…more than likely too cold for ground growing ungrafted varieties. Maybe I’ll stick a couple of lower-value test plants in the ground and see what happens…gotta risk it for the biscuit! It’s gotten down to 0°F the last couple of winters, but even that is pretty solidly too cold.
If I’m not misremembering, things like fleece/row covers will increase the covered area’s temps by about one zone, which is still as low as -10°F!
I’d be interested in hearing y’all’s thoughts on this: planting layers in a big collander, Anderson flat or similar. Heeling those into the ground during the growing season. Pulling them in late summer/early fall and cutting escape roots, then putting them into the same winter protection that all the other trees get when the time comes.
My thought is that taking those escape roots off in early fall and leaving the sides of the container exposed to the air will give enough time for the cut sites to callous over enough to manage temperatures above that root kill temp.
Sometimes we gotta risk it if we wanna get that biscuit!
Glad to hear the additional information. A polytunnel will probably raise the temperature a fair bit more than the porous fleece/row covers. If it is an insulated polytunnel it will probably be even warmer.
My winter greenhouse is 12 x 21 x 7 ft. and the outer layer is 0.006 inch polyethylene film, bubble wrap (0.75 x 0.5 inch tall bubbles) with bubbles against poly and a 0.0012 inch film about 2 inches from the poly. I heat this with a 1500 watt heater to 34F at bench level. The surface ground temperature is 46F and I imagine the temperature couple of inches below the surface would be even warmer. (sorry about only imperial units - I too tired to add SI like I normally do).
I also use a couple of simple polytunnels for my lower value / more hardy trees. I plan to use my two low cost recording thermometers to record air and soil temps. I guess i need to pick up a third so I can do outside, inside, and air.
I have had a bloodgood in the ground in Northern Vermont where it has survived 2 weeks below -10 and that did not include the wind, I am on the edge of 5a to 5b with different sites listening different zones for my location. I believe bloodgood are supposed to be one of the tougher species. Roots in the ground are radically different than roots in a pot. That tree has been in the ground for 10-20 years, it always has winter die back on certain branches but overall the tree seems happy.
I guess the only way to know for sue is to plant it and see what 10 years brings. I have one of the purple lace leaf varieties as a pre bonsai in a 6” deep plastic pot and it has survived 2-3 winters in an unheated cold frame and it wasn’t supposed to. Obviously grafted trees have different roots so you never know what you’re going to end up with.
If possible in your design plant them behind a wind break, fence or other items to break up the wind so they are not getting hammered
Monrovia has a little information on it but you all sorta parsed it out….
A non-grafted Japanese maple (Acer palmatum) is generally cold tolerant down to USDA Zone 5, which means it can usually handle winter lows around -10°F to -20°F if well-established and properly sited. Some sources and gardeners report success even in colder climates (Zone 4), but survival is less reliable and winter protection—such as mulch and wind shielding—is recommended. For most non-grafted types, the upper parts of the tree can tolerate about 0°F, while roots are at risk if soil temperatures drop below about 14°F. Cold hardiness is also affected by site selection, drainage, wind exposure, and plant health.
