How to Winterize Roses: 10 to 12 Inches of Soil Over the Canes

Hybrid tea, floribunda and grandiflora roses do not handle a cold northern winter well on their own. Shrub roses can ride it out, but these three types need a little help before the ground freezes.

To guard them, extension horticulturists in Iowa, North Dakota, Missouri and New Hampshire recommend a mound of soil about 10 to 12 inches high over the base of the canes, built after the plants have gone dormant, and Nebraska’s version runs only a little lower. In Iowa, the work starts in mid-November.

Which Roses Need the Extra Work

Not every rose bush needs a winter blanket. Aaron Steil of Iowa State University Extension and Outreach writes that hybrid tea, grandiflora and floribunda roses, along with some polyantha, miniature and climbing roses, are not reliably winter hardy. Shrub, old garden and species roses are generally hardy and need little or no extra work.

David Trinklein, a horticulturist with University of Missouri Extension, draws the same line, saying old garden and shrub roses such as ‘Knock Out’ tolerate cold well. Sarah Browning of Nebraska Extension adds the Buck rose series to the list of hardy shrub roses that usually skip protection.

Esther McGinnis, a horticulturist with NDSU Extension, explains why the popular types struggle: most hybrid tea, floribunda and grandiflora roses were bred for warmer climates, so they generally need protection to get through a northern winter.

Waiting for Hard Freezes Before Covering

Timing matters as much as the mound itself. Browning writes that extra mulch applied too early prevents the soil around the roots from cooling down as it should, and she waits until after 2 to 3 hard freezes and until all the leaves have fallen.

The University of New Hampshire Extension says to hold off until hard frosts have killed the remaining leaves and the plants have had several nights in the mid-teens. Trinklein’s rule in Missouri is to wait for several hard or killing frosts but finish before the soil freezes, which there usually means early December. Mulching too early, he says, keeps stems warm and moist and can lead to stem cankers.

In Iowa, Steil starts in mid-November by clearing fallen leaves and debris from around each plant, which also removes diseased material that can cause problems next season. McGinnis stresses the same cleanup, since dead leaves left at the base can harbor disease spores.

Building the 10- to 12-Inch Mound

The mound is simple: Steil covers the bottom 10 to 12 inches of the canes with soil, then piles 1 to 2 feet of loosely packed straw or leaves over it. A little soil on top, or a ring of wire fencing, keeps the material from blowing away.

New Hampshire uses the same 10 to 12 inches around hybrid teas and floribundas. Trinklein builds a mound about 10 to 12 inches high and 18 inches wide at the base, covering the graft union, and warns against digging that soil from between closely spaced plants. Bark, wood chips or aged sawdust also work, and he adds more if the mound settles. McGinnis uses a well-drained material such as compost, piled 10 to 12 inches deep over the base of the rose, then adds about another foot of leaves or straw once the compost has frozen, held in place with a chicken-wire cage.

Browning’s Nebraska version is a bit lower, about 8 to 10 inches, and she favors coarse materials such as wood shavings, chopped corn cobs, dry leaves and grass clippings, with a light layer of topsoil on top. Finer materials like manure hold too much moisture, she says.

Pruning before mounding is light. Browning prunes out only broken, damaged or diseased canes. Trinklein cuts tall canes of 4 to 5 feet back by about two-thirds and removes weak, thin canes low on the plant. Other cold-weather chores are collected in the site’s list of outdoor garden jobs to finish before snow arrives.

Climbers and Rose Cones

Climbing roses need their own approach. Browning calls protection for climbers imperative, since most bloom on the previous year’s growth, and says the canes can be laid in a trench and covered with 3 to 4 inches of soil. New Hampshire’s method secures the canes to their support after the first hard frost, prunes off the long ends, and mounds 10 to 12 inches of soil around the base. In sheltered spots, New Hampshire says burlap or evergreen boughs around climbers can be enough.

Styrofoam rose cones have fallen out of favor. McGinnis says a cone traps moisture that can lead to rotting and can heat up on sunny winter days, pulling the plant out of dormancy. Steil also advises against them, because large roses are hard to fit without fall pruning, and the temperature swings inside a sun-warmed cone can cause more winter damage. Browning allows cones only with 6 to 8 inches of soil mounded first, small slits for ventilation, and a heavy weight on top, since the cone alone won’t provide adequate protection.

Watering Through Winter and Uncovering in Spring

Dormant roses still need water. Browning keeps watering until the ground freezes, soaking plants to a depth of 8 to 12 inches every 2 to 3 weeks, and says roses need water during dry winter months when the soil is not frozen.

The cover comes off once the ground thaws. Steil says that is typically between mid-March and early April in Iowa. The site’s list of fall garden dos and don’ts covers the rest of the yard before winter arrives.

For the next few weeks, the job is the same across the cold-winter states: 10 to 12 inches of soil over the canes, built after the first hard freezes, is what carries a hybrid tea, grandiflora or floribunda through to spring.

This article was produced with AI assistance and edited for accuracy against the sources linked above.

Image: HomeinSalem – CC BY-SA 3.0/Wikimedia Commons