When to Prune Roses in North Dakota

Prune hybrid teas, floribundas, grandifloras and repeat-blooming shrub roses in spring, from late April to mid-May, once the buds swell and the winter cover comes off. Prune ramblers and once-blooming old garden roses in summer, right after the flowers fade. Those dates fit the Fargo area. Gardens farther out often run a week or two behind. For the broader picture of getting roses through a northern winter, see growing roses in North Dakota.

When to prune roses in North Dakota

The calendar here is set by frost, and frost arrives late. At Fargo, the reference city for these dates, the last spring frost falls between May 4 and May 15 and the first fall frost between September 25 and October 5. Those ranges come from the 32°F freeze probabilities (the 30 to 70 percent band) in the NOAA NCEI U.S. Climate Normals, measured at an airport weather station. Gardens in the country and the suburbs usually freeze later in spring and earlier in fall, often by one to two weeks.

The USDA Plant Hardiness Zone Map, which sorts the country by the average annual extreme minimum temperature, puts the state mostly in zones 3 and 4, with most of it in 4a. A rose in a zone 3 garden near the Canadian line lives a different winter from one in the southeast corner. So the dates below are a starting point for the Fargo area, and your own yard may sit a week or two off.

What are roses doing in late April?

Rose canes look dead for most of the winter, but the buds along them are only dormant. As the soil thaws and the days lengthen, those buds swell and turn from brown to red or green. Sap starts rising before any leaf shows. If you cut while the plant is still fully asleep, you are guessing which canes lived. If you wait until the buds have swollen, the living canes announce themselves.

For hybrid teas, floribundas and other roses that bloom on new wood, the working window at Fargo runs from the last week of April to mid-May. That lands the pruning shortly before or inside the last-frost range, which sounds risky but is easier on the plant than cutting weeks earlier (more on that below). Where the last frost comes later, the window slides later with it.

How do you know it is time to prune?

Watch the plant, not the date. Roses protected for winter with mounded soil or leaves should be uncovered gradually over a week or so, preferably on cloudy days, once the ground has thawed and hard overnight freezes have eased. Pruning comes after the cover is off. Look for buds that have swollen and started to show color on the lower canes.

Then test a few canes. Scrape the bark lightly with a thumbnail: green underneath means alive, brown or tan means dead. Cut a cane and look at the center. White pith is healthy and brown pith is not. Keep cutting down the cane until the center is white, and you have found where to make the cut.

The date is not the same for every type of rose

Roses flower on one of two kinds of wood, and the right pruning date follows from that. Wood that grew last season is old wood. Wood that grows this spring and summer is new wood. A rose that blooms on old wood has already set its flower buds by the time winter starts. Cut those canes in April and you cut off this year’s flowers.

Which roses bloom on old wood?

Ramblers and once-blooming old garden roses (the kind that put on one big show in June or early July and then rest) carry their buds on last year’s canes. Spring is the wrong time for the main pruning. In April, take out only what winter killed, which you can identify with the scrape test. Then wait. After the flush finishes, prune them right after they finish blooming, taking out the oldest canes and shortening what has grown too long. That gives the plant the rest of summer to grow the wood that will flower next year.

Finish this work before the end of the growing season. Cuts made later trigger tender growth that has no time to harden before the first fall frost, which can arrive at the end of September at Fargo and sooner in the country.

Which roses bloom on new wood?

Hybrid teas, floribundas, grandifloras and repeat-blooming shrub roses flower on growth they make this season. Spring pruning does not cost them flowers. It shapes the plant and sets the height from which the new canes will rise. Repeat-blooming climbers sit in the middle. Their main canes are a permanent frame, and the flowers come on side shoots, called laterals, that grow from that frame each year. In spring, remove dead wood, leave the main canes tied in place, and cut the laterals back.

If you are unsure which group a rose belongs to, check the tag or note when it flowers. A rose that blooms once and quits is an old-wood rose. One that keeps blooming until frost is a new-wood rose.

How far back to cut here

The target height in a cold garden is set by what survived. In milder climates, textbook advice for hybrid teas and floribundas is to leave canes shorter than many gardeners expect. In North Dakota the first job is to remove dieback, and the cut is made below it. Winter often kills canes from the tip downward, sometimes by a few inches and sometimes to the soil line. You cut each cane back to the point where the pith turns white, then a little further to an outward-facing bud.

That can leave a hybrid tea with canes quite short, and some years fewer. This is normal. A rose with short canes in May will often catch up by July, because the growth that follows a hard prune is vigorous. A rose with long stubs of dead wood left on will not. Dead canes also hold disease over the summer.

How far back do you cut Knock Out roses?

Knock Out roses and similar repeat-blooming shrub roses are the easy case. Cut them back in spring, shorter than many gardeners expect. In a cold year the dieback may take them lower than that, and the white-pith rule still applies. Cutting them back hard also opens the center of the shrub, which helps air move through the foliage once summer humidity builds.

For every cut, use sharp bypass pruners and make the cut just above an outward-facing bud. Pointing the bud outward sends the new cane away from the middle of the plant. Also remove any cane thinner than a pencil, anything rubbing another cane, and any cane that looks gray or brown and crumbly.

If a grafted rose dies to the ground and shoots come up from below the graft, those shoots are the rootstock, not the variety you bought. Roses growing on their own roots come back true to type even after a total dieback.

What pruning too early costs in North Dakota

A pruning cut tells the buds near it to grow. If the weather is warm enough, they start within days. Spring in the northern Plains swings hard, and a stretch of warm afternoons in early April can be followed by a freeze in the weeks after. New shoots are soft and full of water, so a hard freeze kills them outright. Pruning in March, or in early April when the mounds are still frozen, invites exactly this.

The damage is easy to recognize. The new red or green shoots go limp overnight, then turn dark brown or black and shrivel. Young leaf tips look scorched. The cane below the damage may still be perfectly healthy, which is why gardeners panic and cut too much.

Wait a few days for the damage to finish showing. Then cut the blackened shoots back to healthy green wood, just above the next live bud, and leave everything else alone. Do not fertilize to push regrowth, because that only produces more soft shoots for the next cold night. The plant has stored energy in its canes and roots and will usually leaf out again, though bloom may come later than usual.

If a freeze is forecast after buds have started growing, cover the plants overnight with burlap, frost cloth or an upside-down bucket, and take the covers off in the morning. The opposite mistake is hard pruning in fall. It wakes buds that have no time to harden before the first frost, so save the big cuts for spring.

Checking this against your own county

The dates above are worked from Fargo, and the state is large. Elevation, low spots where cold air settles, and open country versus town all move the date within it, so two yards in the same county can differ. Rural yards usually trail the airport by one to two weeks.

The simplest local check is to call or visit your county office of NDSU Extension. The staff know the frost patterns in your area and can tell you how far your yard is likely to run from the Fargo figures. In the meantime, use the plant as your guide: swollen buds and a clear scrape test mean it is time.

Common questions

Can I prune roses in March?

No. Mounds and cover are usually still frozen in March and the canes are fully dormant, so you cannot tell live wood from dead. Cuts made then can also wake buds that a later freeze will kill. Wait for swollen buds, which in most northern gardens means late April.

Can I do any pruning in fall?

Only light work. Cut off long canes that would whip in the wind or break under snow, and remove obviously diseased or dead wood. Leave the real shaping for spring, since hard fall cuts trigger growth that frost will kill.

How do I tell whether my rose blooms on old wood or new wood?

Watch how it flowers. A rose that blooms in one big flush in June or early July is an old-wood rose, so prune after the flowers fade. A rose that flowers repeatedly through summer, and keeps going until frost, blooms on new wood and gets its pruning in spring. If you cannot tell, wait until after the first flush before cutting anything but dead wood.

What if every cane died over winter?

Wait until late May, then cut to the lowest living wood. A rose growing on its own roots will send up new canes true to the variety. A grafted rose may send up rootstock shoots instead, which usually have different leaves, thorns and flowers than the plant you bought. If those appear, the original variety is gone and the plant will need to be replaced.