Hardy trees put away for winter

This weekend I finally got my fully hardy trees tucked in for winter. I had hoped to have this done three weeks ago, but such is life.

There's room for a few more, actually.

The shelter I use was thrown up a couple of years ago when we first moved to this house. It's been working OK, but next winter it will be time to replace it. Supports are concrete blocks; the "roof" is a 4'x8' sheet of wooden lattice, wired to a frame of 2X4's. The ground is covered with a flexible perforated vinyl (rescued from the trash at my former employer.)


Species that I overwinter here include:

Under the covering. Cans of mothballs discourage critters.

• ponderosa pine (Pinus ponderosa,)
• Austrian pine (Pinus nigra,)
• yew (Taxus x media,)
• Amur maple (Acer ginnala,)
• Japanese maple (Acer palmatum,)
• two North American spruces (Picea glauca densata and Picea mariana,)
• shimpaku juniper (Juniperus chinensis var. 'Shimpaku')
• and Canadian hemlock (Tsuga canadensis.)

 Once the trees are under the shelter, I cover the whole thing with a "spun-bonded" fabric from DuPont; they sell it for a row cover. It transmits probably 50% of light and reflects the rest, lets water thru slowly, and is advertised to provide "7° F of frost protection." (I'm not entirely sure what that last means; I'd like to think it means the temperature under the fabric stays 7° F warmer than the air outside, but I'm not sure.) My supply of this fabric is getting low; I had to do some piecing to get everything covered. Next year I'll have to look for a supplier, or find a substitute. I'm not sure DuPont even makes this fabric any more.

All tucked in.

The fabric is stapled to the lattice and frame. Stones around the perimeter hold the skirts of the cover down; the pieces of lumber on top are simply for weight, in case of unusual wind. This spot doesn't get much wind, tho: the house and an extension thereof shelter it on two sides; there's the fence on another side, and an old shed (out of sight to the left) on the fourth. Last February we had one nite of true blizzard conditions (as defined by the US Weather Service,) and I don't think winds in the back yard got much above 15 mph!

Two trees, a Colorado spruce (Picea pungens) and a "northern white cedar" (Thuja occidentalis,) are too tall to fit under "the rack;" they overwinter in a sheltered nook nearby, along with some children's play equipment and my ladder. This weekend I plan to go to a friend's property and collect a couple of bushels of fallen pine needles, with which to mulch them.

Both trees are still in development.

I live in the US Dept. of Agriculture's climate zone 5a; this means that in a "typical" winter, we should be ready for at least one nite when the temperature gets down to between -15° and -20° F (-26° to -29° C.) For my non-bonsai friends, a shelter like mine is not meant to keep the trees from freezing: rather, it's meant to reduce destructive freeze-and-thaw cycles as much as possible. Ideally, the trees (rootballs included) freeze once and stay frozen until spring.

I've got some plans for a more permanent structure, for next winter. Stay tuned!