November 2003
Plant of the Month
Rugosa Rose
(Rosa rugosa)
shrub
zone: 3
by Nancy Rose

 Without a doubt, roses are some of the most popular flowers in the world. Roses, especially hybrid teas, are often relegated to separate gardens; however, there is growing interest in using roses more extensively in the landscape. Various shrub roses are gaining popularity for use in shrub beds, borders, and mixed perennial plantings. Rugosa rose and its hybrids have a number of qualities that make them well suited for use in the landscape. They have ample cold hardiness, good resistance to disease, and tolerate salt. Rugosa roses re-bloom throughout the season, providing a long period of flowering interest. Other ornamental highlights include its glossy green foliage and large, colorful hips. Rugosa rose is native to Korea, Japan and northern China. This rose has been carried to gardens around the world and has naturalized in some areas, such as the northeastern United States. In its native habitat, Rugosa rose grows primarily in sandy seashore area. Rugosa rose’s tolerance of salt is critical in that environment, since it is subjected to salty sea spray. Rosa Rugosa is one of the hardiest of roses, rated cold hardy to USDA zone 2 (average winter minimum temperature of –45° to –50° F). Unfortunately, not all of the hybrid Rugosa cultivars have retained this extreme level of hardiness. In testing at the Minnesota Landscape Arboretum, hybrid Rugosa cultivars showed mid-winter hardiness levels ranging from below –40° to –20° F. This still puts most of the hybrids in an acceptable range for most of the upper Midwest, though there may be some can dieback. The height of the species and hybrids ranges from 3 to 6 feet, with an equal or greater width. Rugosa roses have a distinctly dense, twiggy growth habit, with many bristly canes. The overall outline of the plant is irregularly rounded. One outstanding ornamental feature of Rugosa rose is its glossy dark green foliage. The pinnately compound leaves have 5 to 9 individual leaflets. Deeply impressed veins on the leaves create a distinctly rugosa (wrinkled) appearance, hence the species name Rugosa. The foliage of Rugosa rose often develops an attractive yellow to gold fall color. The dry foliage also tends to persist on the plant throughout he winter, adding a little textural interest to the winter landscape. The flowers of Rugosa rose and its hybrid range from single to semi-double to fully double, and in color from white to pink, red, magenta and pale yellow. The flowers are 2 to 3 inches in diameter and are borne singly or in limited clusters. The bright yellow stamens in the center of the flower provide a striking contrast. Many of the rugosas are deliciously fragrant, a trait well worth selecting for. As with many roses, Rugosa rose puts on its heaviest show of blooms in June. It then has periods of re-bloom through the rest of the summer and early fall. Some of the Rugosa hybrids have limited re-bloom, which makes them less valuable for landscaping use. Large showy red-orange hips follow the flowers, though not all of the hybrids have good hip production. Rugosa rose is known in some places as “tomato rose” or “beach tomato” for these large edible fruits. The fruits can be used to make jam. Roses are notorious for the susceptibility to various disease and insect problems. While Rugosa roses are not immune to these problems, they have far fewer troubles than many garden roses. In particular, Rugosa roses are blessed with good resistance to two of the worst foliar diseases of roses, blackspot, and powdery mildew. Disease resistance amongst Rugosa hybrids ranges from excellent to mediocre. Rust can be an occasional problem. Several insects can plague Rugosa roses, the two most serious being rose stem borers and a small wasp that causes mossy rose gall. The best control method for both of these insect pests is to carefully prune out damaged canes and galls each fall. Infected prunings should be disposed of rather than composted. Aphids, mites, and various leaf -chewing insects can be temporary pests but usually are not severe problems. Rugosa roses grow well in a range of soil types. They will tolerate fairly dry, sandy soils, but their best growth occurs when growing in moist, well-drained soil amended with organic matter. A sunny site with good air circulation is ideal. Rugosa roses can be planted individually in mixed rose plantings and in perennial gardens, but they are showiest when planted in large masses. Just remember to leave enough space to get in to do pruning. There are many hybrid Rugosa rose cultivars available. One of the very best cultivars is ‘Frau Dagmar Hastrup’, with fragrant, light pink flowers and excellent red hips. Good white flowered cultivars include ‘Albo-plena’ and ‘Blanc Double de Coubert’. Check out the Rugosa roses at various local rose gardens to see which are your favorites. By Nancy Rose, Minnesota Landscape Arboretum
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