Tree roses must be protected in winter in zones 6 and north
Giving advice on protecting rose standards is difficult at best. Every rose variety has a little different degree of tolerance, and winter conditions in any given zone or region is highly unpredictable. Especially with rose standards it is always best to over protect, especially in the first couple of years until the plant is well established and begins to adapt to its’ conditions.
There are some basic guidelines and lots of ideas, as you experiment with your own standards you may come up with some good ideas of your own. (And we would love to hear about them!) Let’s start with the easiest for warmer climates.
All zones:
First, prepare the tree for “cold storage”. If freezing weather has not already caused all foliage to drop, snip off any remaining leaves. Pruning lightly to reduce crown size if you like. Spray entire tree thoroughly with dormant oil, including the surrounding soil. Dormant oil will protect your standard from insects that may try to spend the winter with inside the winter wrapping. Be careful of overspray near the house, dormant oil can sometimes stain siding. Inspect the trunk and graft unions for holes or cracks, fill them with grafters wax to further protect from insects.
Zone 8:
Frost will not hurt your tree rose, but more severe cold will damage the grafts. Certain varieties of roses are not at all cold tolerant, so even the grafted rose crown could be damaged. In zone 8 your standard may be just fine left planted outside without protection. If your particular region freezes on occasion, some protection is a must. Do not apply protection until the weather is cold enough to render your standard dormant. To protect the root graft, mound mulch up 6-12” at the base. Use burlap bags to cover the crown and top graft. Do not use plastic sheeting, it does not breath and conducts cold well. You could also use the white fabric row covers, but I would avoid dark materials such as landscape fabrics. The dark color will attract and trap heat, which can cause your rose to try and grow.
Zone 7:
In zone 7 it is unlikely that your standard will survive without protection. Freezing weather is always likely. Do not apply protection until the weather is cold enough consistantly to render your standard dormant and the soil is cold. First apply dormant oil spray as mentioned above. To protect the root graft, mound soil up 6-12” at the base and cover with mulch. Heavy mulch piled high may be enough in certain regions, especially zone 7b. Use burlap bags to cover the crown and top graft. Do not use plastic sheeting, it does not breath and conducts cold well. You could also use the white fabric row covers, but I would avoid dark materials such as landscape fabrics. The dark color will attract and trap heat, which can cause your rose to try and grow. Fill the bag or other fabric covering with shredded leaves or straw. Do not use hay, it is full of weed seeds, however salt marsh hay is recommended by some gardeners. Just don’t buy a bale of “Halloween” hay, that is strictly for decorative purposes. And if you want to use other mulching material, buy it in bags so there are no insects in it. It is also a good idea to spray hay or leaves with dormant oil if you suspect the possible presence of insects. To install the covering, open up the burlap bag at both ends, secure one end around the trunk below the graft and fill the bag from the top. Then secure the top of the bag with clips or clothespins. If using rolls or sheeting materials, create a cone shape wrapping with it opened up wide at the top and secure around the trunk below the graft. You may need some help with this to make it easier to manage.
Zone 5, 6 and 7:
Before moving on to the most extreme protection method, “caging” your standard has become a common way to protect standards in zone 5, 6 and 7. It would be a good idea to check with other gardeners, local nurseries or your local university extension service to find out if this method is effective in your region. It may, in part, depend on the hardiness of the rose that is grafted to your standard.
First apply dormant oil spray as mentioned above.
Wrap every possible inch of the trunk and grafts with insulated pipe wrap. It is available in hardware stores in a polyethelene tube that is slit to slip around a pipe, or as a foam “tape” wrap. (It is also available in a fiberglass wrap - don’t use that one.)
Next, protect the roots and lower graft by mounding soil a foot high at the base of your tree rose, extending the mound well over the root area. Then mulch it heavily.
Then you need to protect the rest of the tree. Form a cylinder around the tree with tall chicken wire fixed around tall stakes. Or fix it securely to the ground with stakes - or the long “staples” made for securing mulching fabric work well. Use the stakes or staples every several inches around the cage so the wind does not catch the cage and pull it out of the ground.
Fill the cylinder with shredded oak leaves, straw or other mulching material, completely covering the tree. Do not use hay, it is full of weed seeds, however salt marsh hay is recommended by some gardeners. Just don’t buy a bale of “Halloween” hay, that is strictly for decorative purposes
Finally, double wrap the “cage” in burlap or row cover fabric. Secure it with twine tied around at several points up the length of the cage, or with clips. Do not use black landscaping fabric as it attracts heat and may encourage your rose to grow.
Some gardeners swear by a wrapping of bubble wrap, covered by burlap to avoid the problems of conductive plastic. The bubble wrap can be used INSTEAD of the cage, but it is more difficult to work with. Generally the bubble wrap is applied in an inverted cone shape secured below the top graft. Bubble wrap should NOT be closed tightly at the top so that air circulation is not completely inhibited, and heat from sunny days gets trapped.
If you have a variety that in shrub form is hardy in zone 5 or 6, this method should protect the tree form adequately in zone 4. But, be sure and ask the “locals” for advice.
Zone 5 and 6:
The Minnesota Tip is the best method of protecting rose standards from extreme cold. This method is usually used for hybrid tea roses grown in zones 5 and north, as well as more tender grandifloras. Dig a trench beginning at the base of the bush, and extending out from the base slightly further than the height of the plant. (The trench should surround the root ball, but not expose the roots.) Gently pulling the crown branches in toward the center, tie the bush up beginning at the base, winding twine around the rose crown to hold the branches together. You may first prune back lightly to reduce the size of the crown first. This may help you bury it more easily. For a tree rose, you should push a sharp spade in sharply, slightly at an angle under the roots. This will nearly “dig out” the root ball so that the trunk does not snap when you tip it into the trench. Now tip the tree gently into the trench, leaving the roots in place as much as possilbe. Cover the entire bush with the soil you removed, then cover deeply with leaves, mulch, or bags of leaves over the entire area.
If the area around the standard does not allow space to tip and bury the tree, it will have to be dug out completely to move elsewhere. This is not ideal, as it will somewhat retard its growth next spring, but is better than losing the tree to winter. Bury the tree in your now empty vegetable garden if you have one. This is a perfect, available, easy to dig in spot to store your rose standard. Also a great spot to bury a potted rose standard, pot and all! By the time the soil is ready to till for planting, your rose will also be ready to come out for the season. If you do not have a vegetable garden, pot up the tree and store it in the garage, as detailed next.
Winter Protecting Potted Standards:
If your rose tree is in a container, you can bring it into the garage after the leaves have fallen if your winters don’t get too cold. This should be adequate in zone 6 and 7, and perhaps zone 5. A cold corner of an unfinished, preferably unheated basement works well in colder zones north of zone 6. If it is even minimally heated the tree may not go dormant, in which case lack of sunlight and water may kill it as it tries to continue growth. Temperature should be between 32 and 45 degrees, and you will want to give it MINIMAL water to keep the soil from going completely dry, and NO fertilizer. Or leave it in the garage and wrap the entire container including the bottom with a heavy blanket. Then wrap the entire tree with burlap or other fabric. Up here in zone 4, my garage is not heated and temperatures drop to 30 below zero or more, probably colder when the door is open a while. I would create a cylinder of a heavy kraft paper or chicken wire and fill it with mulch or oak leaves, entirely covering the tree, as well as wrapping the “cage” in burlap. The container itself should be raised up off the concrete floor and wrapped in a blanket. This can also be done with the container outside in zone 6 or maybe even zone 5.. In the garage it is out of sight with a tad more protection. If it absolutely must be left outside in zone 4 or 5, push the whole protected container up against the foundation of the house to benefit from the heat of the house. Or place it up against a patio door - we lose a lot of heat through glass and your standard will make good use of it.