Zone 4 is a climate zone covering the northernmost states of the US. This includes Wisconsin, Minnesota, North Dakota, and Montana. These states have short growing periods and particularly cold winters. As such, there are a limited number of shrub roses capable of growing in zone 4 and, even then, it may be necessary to bundle shrub rose blooms during cold snaps to keep them from freezing and crystallizing.
Blanc Double de Coubert Rose
The blanc double de Coubert rose bush was first developed in 1892 and is popular in the northern U.S., Great Britain, and northern parts of France. It grows 4-6 feet in height and has extremely thorny, grey branches. It blooms as early in the year as February and, like the name suggests, presents a double "bloom-in-bloom" of pure white. This is an extremely hearty breed which is resistant to common rose fungus and most insects, though it is allergic to commercial fungicides. In addition to high cold weather tolerance, this shrub rose can withstand salt air and sandy soil.
The hansa shrub rose is of a similar descent to the blanc double de Coubert, being an offshoot of the rugrosa. As a result, it shares all the same resistances as well as the weakness to fungicides. The flowers are blooms-in-bloom of a deep red running to violet at times, budding in clusters on short stems. Though the hansa blooms primarily in late March, it has a number of minor blooming periods throughout the year. The foliage is large, crinkly at the edges, and a deep green. Blooms have a strong aroma of old rose tinged with clove.
Morden sunrise is a full-sun species of shrub rose that thrives in zones 3-7. It only grows to 3 feet high, but spreads outward quickly. Cut the branches back every few months to thicken the light green foliage. Rose hips are very thick and grow on long stems with very few thorns. It's resistant to disease and infestation, but requires frequent high-acid fertilization for optimum growth. The hips are a creamy orange, though the blooms themselves, which come in April are more yellow, like the sky during sunrise. Wrap the blooms in winter, but even if they die off, the next year's crop will be just as large and colorful as the first.
Redleaf rose is a rose shrub native to southern Europe and can withstand extremes of heat and cold, making it suitable to zones 2-8. It is a thick-stemmed variety, growing as high as 6 feet at maturity and able to handle powerful winds. As the name suggests, the stems and leaves are all a red-green color. It flowers in late spring, producing a sugary pink bloom with a yellow stamen in the center. These flowers are edible, meaning they can be the source of attack from insects and local wildlife.