Winterizing Trees

by Mary Jasch

Winterizing tender trees and shrubs may seem daunting, but the process and result are artistic, functional and life-saving aspects of tending a garden. Myron Porto, horticulturist with Shanti Bithi Nursery in Stamford, Connecticut, describes the methods they use at a private garden in Mount Kisco, New York. Judy and Michael Steinhardt own the property and open it to the public twice a year on Garden Conservancy Open Days.

Shanti Bithi staff wrap tender trees and shrubs that are marginally hardy for this Zone 6/Zone 5 property and also those planted within the last two years. Some broad-leafed evergreens are wrapped to protect leaves from wind damage and keep them looking good till spring.

Boxwood
In a garden area called “The Ruins,” stone walls and fireplaces are all that remain of the former home of American novelist/journalist Theodore Dreiser. The garden is now a playground for the Steinhardts’ grandchildren and other young visitors. Gorgeous plantings reminiscent of young junipers in an old field and a large circle composed of six triangular pie-wedge shaped flower beds dotted with dwarf Kingsville boxwood (Buxus microphylla ‘Kingsville’) at each point, create a romantic air.

To protect the 18 boxwood, hardy to Zone 6, Porto and staff sprayed them with Wilt-Pruf Anti Transpirant in early December while temperatures were in the 50s. That produced a good coating that dried in time before the weather turned cold. They added 6-8 inches of leaf mulch around each root zone, placing it close to the trunks.

“We have so many leaves on the property and we grind them up,” Porto says. “The idea is to keep things looking very natural around here, to try to get it to blend with the environment. There’s a lot here, but we don’t want it to look like it doesn’t belong.”

Next, they made a tee pee by pounding 1”x1” sticks in the ground and double wrapping them with burlap to keep the wind off. In high winds, burlap keeps the plants slightly warmer, too.

Nearby, a 10-foot tall boxwood by a stone tower is wrapped in an open manner because a teepee would have to be too wide in order to be tall enough to enclose the plant. Instead, a plywood “hat” is placed above the wrapped plant to keep snow from accumulating inside because boxwoods have a tendency to split open.

The fastigiatas (B. sempervirens ‘Fastigiata') are only Wilt-Prufed. “They should be fine. When it snows we just come and knock the snow off them.”

Rhododendron
Near the lodge, past a wildflower meadow and hillside of Christmas fern, hardy rhododendrons are loosely wrapped in burlap to block the cold, dry winter wind. A few delicate plants get closed at the top. But first they all receive the treatment: Wilt-Pruf and crushed leaves.

The pathway through the lodge’s garden beds is covered in Eastern white pine needles collected from a local golf course. Needles cover walkways through the property including the maple and woodland gardens. “Again, it’s very natural, very organic and it’s nice to walk on. It’s nice and soft.”

Needles and chopped leaves are perfect for the property’s natural areas and plantings. Shanti Bithi plants only acid-loving plants here, on this naturally acidic soil.

Newly Planted Trees
Leaf mulch is tucked around new plants to protect them through one or two winters so the root zone doesn’t freeze solid or deep. The wrappings of newly transplanted balled and burlapped tree are left intact for protection against high winds. Large trees have a tendency to move in wind until they’re rooted. Nursery staff uses natural, untreated burlap that will decompose. The above-ground wrappings around the trunk will be removed in spring.

Maples
In the fall, staff cleans up leaves from all plantings and naturally growing trees and shrubs. They grind them up to break down better, then top dress the Steinhardt Maple collection of over 400 cultivars. The smaller, more delicate Japanese maples, larger marginally hardy varieties, and those planted within the last two years are wrapped for winter. Their trunks and main branches are wrapped with 4-inch wide burlap bandage that comes on a roll.

Larger maples and those that have lived on the Steinhardt property for at least two years are generally hardy and sturdy enough to survive winter without help.

A small grove of red snakebark maple, Acer conspicuum ‘Phoenix’, lights up winter with bright salmon-colored bark. Not yet established and a little tender, the trees are wrapped from their lower branches downward. “When they establish themselves they should be okay. We really don’t want to wrap them because the feature in the wintertime is the salmon bark and if we wrap them you can’t see it,” Porto says.

A loose burlap rectangle is erected around Zone 7 Nandina to protect it from wind. Across from it, creeping phlox, Phlox stolonifera, looks pretty in green at the base of paperbark maple Cinnamon Flake.

“A garden takes on a whole different personality in winter and I love it,” Porto says excitedly. “You see things in winter that you don’t see during the regular part of the year and there are features that most people, I think, don’t really think about. Like the bark on trees, the branching patterns on trees, the way the light hits things in wintertime. You look at the light now. It’s very soft, long shadows. It creates a whole different feel for the garden. I love the garden during the wintertime. Also when it snows, and plants are layered with snow. It’s beautiful like the conifer garden in wintertime is gorgeous. Everything looks like they’re frosted.”

Camellias
On the way to the camellia collection, chopped leaves cover the planted and wild ground. Pine needles on walkways contrast nicely. The leaves will add nutrients and organic matter to the soil and prevent washout on the stream bank, and plants will grow right through them come spring.

Camellias get special treatment on the Steinhardt property. The 100-plus collection comprises the fall-flowering Camellia japonica and its crosses with the fragrant, spring-blooming tea oil camellia C. oleifera, both hardy to around 0 degrees. “If you can get them to come through several winters they’ll be ok,” Porto explains. There’s no need to worry about japonica buds surviving winter, since they just finished blooming, but oleifera buds are touchy, so when Porto sprayed them with Wilt-Pruf, he hit the buds heavy. Staff tied the plants close, tucked them in with leaf mulch, then wrapped them in two layers of thermal blanket row cover fabric. It will keep the plants a few degrees warmer than ambient temperature on this protected slope in bright light.

On the woodsy banks along the “Duck Preserve,” large shrubs and trees are wrapped like ghosts, such as cherry laurels so they don’t burn back. But some special trees are not. Take Stewartia with its beautiful bark, left undone to add to winter’s beauty and stand up and be noticed.

“In my opinion you can look at a garden year-round. There’s always something to look at. You may not notice the bark during the summertime when it has flowers on it but during the winter it really stands out. Your garden goes year-round. You have to appreciate it for what it is year-round,” remarks Porto.

And there are surprises. “Guess which tree is the real living tree?” asks Porto.

“Real tree?” wonders the visitor, looking at tall conifers with bright green needles. Creative thinking is the name of this game as Porto reaches through thick branches and touches the trunk of a Chinese fir, Cunninghammia lanceolata. The marginally hardy China fir is too tall to wrap, so staff cut and “planted” spruce trees around them to minimize wind.

“It’s a natural protection. We came up with this idea of setting these around it and into the tree like the cunninghammia is growing within the spruce. By mid to late March all of this comes off.”

Other wrapped, young trees and shrubs include a podocarpus look-alike, Cephalotaxus fortunei, a.k.a. plum yew, hardy to Zone 7, and a tall, marginally hardy Florida Torreya, Torreya taxifolia. Both get sprayed with Wilt-Pruf and tucked in with leaves. So does an evergreen magnolia with 10-inch leaves. “The buds probably would be ok. I’m more concerned about the foliage. I don’t want it falling off and looking ratty.”

Flower Gardens
Douglas fir boughs cover the daylily garden, alpine garden and flower beds to help maintain a consistent soil temperature. Other beds, like a slope planted in ferns and toad lily are covered in chopped leaves.

A grove of Crepe myrtles (Zone 7) makes an artistic statement on a hillside. First, a wire cage is fashioned around each trunk and filled with leaf mulch. Then branches and trunk are padded with hay (it holds up better than straw) and wrapped with burlap. Porto says they are now pretty well established and in the future may not be wrapped.

“We try to make everything look good in the wintertime. I like it when Mr. Steinhardt goes out in his garden in the wintertime and just doesn’t say ‘Ok, it ended in late November and I’ll come back again in March.’ No, you can you look throughout the year.

“Mr. Steinhardt likes to challenge. If we say we can’t grow it here, he’ll say ‘Let’s try it. Let’s see if we can do it.’ For him that’s always a real thrill because we’ve done something that maybe we shouldn’t be able to do.

“Winter has a certain beauty to it. I really appreciate all of this stuff. For me I can look at it and say I find beauty in this too. It doesn’t need to have leaves or flowers on it. You really see the structure of a garden then.”

Visit the Steinhardt garden in spring and summer on a Garden Conservancy Open Day. Check here for the schedule: www.gardenconservancy.org

Shanti Bithi Nursery: www.shantibithi.com

**All photos by Mary Jasch

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