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Winter Protection

For Your Roses

by Ryan Tilley

 

In the northern states, winter protection for roses is a really big deal. Items such as rose cones are used to keep out the cold. Roses, especially tree roses are dug slightly and laid on their side and buried with soil. Soil is piled up a foot high around the base of roses to protect the bud union. Roses are planted with the bud union 2 inches below the soil. It is a lot of work to keep roses alive until spring!

Here in the south, we have it easier. Temperatures usually stay in the 25 to 50 degree range during the winter with only a few nights where temperatures drop into the teens. (The north Georgia mountains are of course a bit colder). Back in the mid 80's there were a few years in a row where the temperatures dropped near zero or below. In fact, the temperature at my house in northern Atlanta hit a frigid minus 15 one morning!  But these extremes are the exception and do not need to planned for on a yearly basis.

So for most of us, the task of winter starts with mulch. Roses should be mulched after the soil has gotten cold. This means after several hard freezes have occurred. The goal of mulching is to keep the soil uniformly cold until late winter. If mulch is applied too early, it will take the soil longer to cool and the roses longer to enter semi-dormancy making them more susceptible to cold damage. November tends to be mild in Georgia and much of December passes with temperatures in the 50s and 60s. So in a normal year, mulch should be put down in late December and in some years even as late as early January (a few weeks earlier in the mountains). Having said this, I keep an eye on the weather forecasts throughout December, which is easy for me since I was meteorologist for over 20 years. If there is going to be a sudden plunge in temperature, say from the 60s into the teens or low 20s before the roses have gone dormant or semi-dormant, I will mulch the rows before the cold snap. Roses suffer the most damage when the sap is still flowing and a very hard freeze occurs. (It was 14 degrees at my house on Nov 22 this year.)

The mulch I prefer is pine bark mulch (not nuggets). It is easy to apply, looks good, and doesn't retain excess water. Other hardwood mulch like cypress, pine mini-nuggets, or eucalyptus also works well. I will mound 6-8 inches of mulch over the bud union and lower canes. For the rest of the bed, I like to put a 2-3 inch layer of aged horse manure on. The organic matter is good for the soil and provides good insulation. Be sure that if sawdust shavings the manure is in is fairly well rotted. If not, it may leach some nitrogen from the soil as it decomposes. This can be counteracted by adding extra nitrogen to the bed in late winter. If manure is not practical for you, just add a 2-3 inch layer of the same mulch you used on the roses. 

About the same time you apply the mulch, spraying an anti­transpirant like Wilt-Pruf or Vapor Guard is beneficial. This spray is used to help keep moisture in the canes during periods of cold, windy weather. As much damage is done to roses from drying out over the winter as is done from cold weather. This is also an excellent spray to use the day before a severe cold snap is forecasted to occur. Anti-transpirants, also have the advantage of helping to prevent blackspot spores from penetrating the leaves as well as leaving a very attractive shine on the bushes. I usually make two or three applications as each application will last about a month or so. 

You will want to leave the mulch on your roses until the main pruning time in late February or early March. But keep it close by in the rose bed because quite often there is a major March freeze where temperatures drop from near 80 into the teens or 20s. In fact, this when much of the severe damage to your roses may occur. At this time, an application of an anti-transpirant and re-mulching of the roses is necessary. Remove the mulch when the freezing temperatures have passed and pray that it won't happen again! 

Another beneficial thing to do to your roses, especially hybrid teas, is to reduce their size to about 4 feet. Winter winds blow hard against tall canes, rocking the bush and slowly loosening the roots allowing cold air to the area below the bud union. These winds may also break tall canes that have not fully hardened off yet, further exposing lower parts of the bush to cold damage.

As for roses on fortuniana rootstock, I take a slightly different approach. The misconception that these roses are not as hardy as roses on other rootstocks is not quite true, However, they are typically sold when they are quite young and by the time the first winter rolls around, the bud unions are not as fully developed as roses on other rootstocks that were sold as two year old plants. So the first winter only, I take an 18 inch high section of chicken wire and make a circle around each bush. I use the end of the wire to fasten it. Then I fill it will pine mini-nuggets to a height of 12­15 inches. I do this about the same time I mulch the other roses. I leave the mulch in place in the chicken wire until early March. Then I remove the mulch, but leave the wire in place in case the big March freeze comes. At that time, I will simply fill the wire cage again until the cold weather passes. This method is extremely effective and I have not lost one rose when it was treated this way. The following winter, I will treat these roses the same as I treat all of the other roses.

Some roses are notoriously winter tender and may need a little extra protection in the form of extra mulch or even piling soil over the lower 8 inches, especially in the colder northern mountain areas. A few roses that I have found to be more susceptible to winter damage are Dolly Parton, St. Patrick, Color Magic, Moonstone, White Success, Chrysler Imperial, and Jenta.

The final task you need to do protect your roses is to water them regularly during dry spells and especially the day before a big cold snap. When the soil is frozen, the roots can't supply water the plant. So watering the day before a big freeze will ensure that the canes have plenty of water to weather the storm.

So that about does it. Depending where you live, you may need to adjust the timetable a bit for mulching roses. And if we do get an unusually cold spell where the temperature drops near zero, you may need to mulch a little higher on the bush or actually use soil for the tender varieties.