In past years our ground is frozen to a depth of 3-4 inches by the middle of December making it possible for us to start the process of mulching roses and strawberries to give them a blanket of protection against the winter cold and spring frosts.
As of Tuesday when I was writing today's column, the ground on the north side of my home was only frozen to a depth of an inch. And that was in the shade where the winter sun doesn't reach.
Since it so close to the holidays and most of us are out shopping and still putting up decorations we might as well wait until after the first of the year to start this process. Waiting until after Christmas also gives us another use for the Christmas tree; using the boughs to hold down the mulch we apply over our strawberries.
Varieties of hybrid tea and other roses grafted to a different root system are especially sensitive to winter injury. Roses killed down to the graft union will usually come back from buds off the roots resulting in a totally different variety of rose. Some years only part of the tea rose is killed resulting in only part of the bush producing flowers of the variety you paid good money for. The dead portion of the bush may be replaced with suckers from the roots that produce blooms of a different size, shape and color.
Root suckers are easy to spot as these shoots will have different shaped and sizes of leaves and be much more vigorous than the stems of the hybrid tea. Replacing dead tea rose and those that are being overgrown with root suckers is often necessary when they aren't mulched for the winter.
Some rose companies provide hybrid tea roses on their own roots. Even if they die down to the ground during the winter they will usually come back from below-ground buds resulting in the same variety of rose. This certainly eliminates the need to mulch your roses. Forgetting about hybrid tea roses and planting shrub roses and others growing on their own roots is another option to avoid winter damage. You can also consider hybrid teas as annuals and just replant them every spring, but that can be expensive.
To avoid the dieback of grafted hybrid tea roses, the plants should be mulched as soon as the ground is frozen to a depth of 3-4 inches. The purpose of the mulch is to keep the ground cold and protect the stems and graft from the drying effects of the winter sun and wind. Some people mound their roses with soil, others use leaves or straw. The 12-inch pile of mulch placed over the bush can be kept from blowing away with boughs cut from your Christmas tree. If you don't have a Christmas tree maybe your neighbor might donate their tree to the cause.
Your strawberry patch will also benefit from a layer of winter mulch. The freezing and thawing of the soil is hard on these plants breaking roots every time the soil moves when temperatures fluctuate. Broken roots create ideal avenues for soil-borne plant diseases to attack the roots and crown of the plants. Such damage may not be noticed until the plants start to fruit and collapse and die.
The mulch on your roses can be left on until about a week or two prior to the last killing spring frost. The plant will have already started to develop shoots under the mulch prior to that date so remove it with care to avoid breaking any of these new stems.
The mulch on a strawberry patch can be left on until new leaves start to develop and then moved to the side so it is available to quickly cover the plants when a hard freeze is expected. Strawberry plants that set flower buds in the fall need a little extra protection in the spring to ensure you don't lose that first or only crop of berries. Mulch provides that protection.
Dr. Curtis E. Swift is a retired horticulture agent with the CSU Extension. Reach him at Curtis.Swift@alumni.colostate.edu or check out his blog at http://SwiftsGardeningBlog.blogspot.com. He owns Swift Horticultural Consulting and High Altitude Lavender.