Rugosa Hybrids

My rugosas are in full bloom right now. I have a hundred foot long bed of them. What a sight and what a scent. Rosa rugosa is a species rose from Japan, Korea, north east China and the Russian Pacific Coast. It ranges in height from three to eight feet tall. The flowers are single and reddish purple or white. R. rugosa was introduced to Europe in the early 1800s. There was no hybridizing done with it until the end of the 19^th century. Most of that early work was done in France. They range in height from about two feet to eight feet tall. The blossoms may be single, semi-double, double or very double. Colors are reddish purple, pink, white or yellow. Rugosa hybrids are among the hardiest repeat blooming roses. They can be used in a mixed border or as specimens. The lower growing varieties can be bedded out. They are especially useful along roads where salt tolerance is a requirement. Although they suffer in alkaline soils, they can handle poor soils. These roses do not get any foliar diseases. Japanese beetles do love them. Do not spray them though, as their rough foliage is sensitive and will burn if sprayed even with a foliar feed.

There are usually only a few varieties offered in most nurseries. I have over 30 different rugosa hybrids growing here. The biggest of them all and one of my favorite roses is Sarah Van Fleet. It was hybridized by Dr. Walter Van Fleet in 1926. This rose grows to over eight feet tall and six feet wide in my garden. It starts blooming in early June. This year it started blooming Memorial Day weekend. It will continue to bloom until a hard frost. Sarah Van Fleet has a fragrance more like an old rose. The blooms are semi-double and medium pink in color. They fade some as they age. It does not set hips. This rose is extremely thorny. Wear a canvas jacket and gloves with gauntlets when you prune it. There will be some dieback (no more than 10%) after a very cold winter. This rose could be the focal point of a mixed border. It is in my border. Sarah Van Fleet would make an impenetrable hedge. The shortest rugosa hybrid and another of my favorites is White Roadrunner. This rose was developed in Germany by Kordes in 2001. It doesn’t grow more than two feet tall and has semi-double white flowers. The yellow stamens look great against the white petals. It is self cleaning, i.e., the petals fall off on its own. It does set a heavy crop of large, bright red rose hips. This rose also looks lovely in a mixed border. You might choose to line a path or driveway with it, as the white blossoms aid visibility at night.

Snow Pavement, AKA Schneekoppe was hybridized by Baum in Germany in 1984. Suzanne Verrier, in her great book, Rosa Rugosa, says the flowers are the color of “a drizzle of blackberry syrup in heavy cream.” It is heavily scented with a mix of rose and clove. This rose gets to be about four feet tall and as wide. Plant it near the edge of a border so you can stick your nose in a blossom as you walk by.

Rugosa hybrids are low maintenance roses. Give them a bucket of compost once a year as a top dressing and mulch them heavily to keep the soil moist and weeds down. Once established, prune about a third of the old canes to the ground every spring to encourage new growth. Own root plants will sucker and spread. They can be divided and replanted in the spring as soon as the ground can be worked. They do look lovely in thickets and drifts. For a list of the ones I grow see the Roses We Grow Page (click on the green icon to download an Excel spreadsheet) on our website, http://www.derrosenmeister.com/ For in-depth information on this wonderful group of plants, check out Suzanne Verrier’s book, Rosa Rugosa.

Cold Hardiness- What does that really mean?

A winter like the one we just had puts roses through their paces. As I was pruning this spring, I found it fascinating to look at the range of winter damage in the cold hardy roses I grow. Some had no dieback at all. At the other end of the spectrum are the few that die back to within inches of the ground. Why is that, when these roses are listed hardy to zone 5?

Cold hardiness is the lowest temperature a rose can live through without injury. Varying amounts of dieback could the result of growing conditions the summer or fall before, as well as what the spring is like. Roses are better able to withstand a cold winter after a good growing season. It allows them to develop good rooting and branching systems and store food for the coming year. Roses that produce lots of new growth late in the growing season are more prone to damage. New wood does not have time to harden off. Roses need a gradual cooling in the fall to acclimate to the cold. See saw temperatures interfere with this process. A gradual warming in the spring is just as important to minimize damage. Early warming triggers some roses to bud out earlier and those buds can be damaged by the colder temperatures that soon follow. So the answer to the question is- some varieties are programmed genetically to adjust their physiology to cold weather better than others.

Some cultivars have no dieback at all. Roses that lose no more than ten per cent of their growth are called tip hardy. Once-blooming roses need to be tip hardy. They bloom on old wood (last year’s growth). If too much of that wood is destroyed, they will not flower. Roses that repeat bloom flower on both old and new growth. They can withstand more dieback and still flower well. Vigorous repeat blooming roses can die back to the ground (crown hardy) and still flower on the new wood produced that year. One needs to ask/know not only whether a rose is hardy in a certain zone, but whether it is tip hardy or crown hardy in that zone and whether it is a once bloomer or repeat bloomer.

I find that using crown hardy roses for groundcovers makes spring cleanup much easier. I cut off the damaged canes within inches of the ground, do whatever weeding needs to be done and reapply a heavy layer of mulch. The weeding and mulching would be painful operations if those same plants were tip hardy, as I'd have to be working under and around them. By June the ground between the roses will be covered with canes and flowers. I like the rest of my roses (shrubs, climbers and ramblers) to be at least tip hardy, as I like substantial plants. There are always exceptions, of course. Antike 89 by Kordes is the one climbing rose I grow that loses many/most of its canes each winter. It has very double, bi-colored blooms and shiny, dark green foliage that stays clean all season. This year, it died to the ground. By June, it will be at least 6 feet tall and covered with blossoms. By September, it will be 8-10’ tall. The new growth is extremely vertical, so it works well as a pillar. The canes are too stiff to fan out on a trellis or wind around a chain for a catenary.

It’s all about knowing the right rose for the situation you have. If you have any questions about what is the right rose for you, please ask.