Flower forms range from single to semi-double and double. Single flowers are typically comprised of four or five petals with a semi-double flower ranging from six to 14 petals. Double flowers have 15 or more petals that can go up into the hundreds. According to the University of Minnesota Extension, “Flower form is a function of petal count and petal length.”
Grape-leaf anemone (Anemone tomentosa "Robustissima") is a late summer-blooming perennial flower that produces masses of single, pale pink to violet blooms. The five-lobed flowers have a slight cup shape and a ring of yellow stamens that contrast with the petals. They grow in upright clumps and have a moderate growth rate. Grape-leaf anemone grows 1 to 3 feet tall and wide and makes an ideal cottage garden plant to grow along a flowerbed or border. Grape-leaf anemone grows best in full sun to part shade and well-drained, fertile soil that is moist. They are suitable in USDA zones 4 to 7.
Japanese rose (Rosa "Blanc Double de Coubert") is a shrub that produces a fragrant, white, semi-double flower that attracts butterflies and birds to the garden and is often followed by orange hips. It grows 6 to 10 feet tall and wide and has a moderate growth rate and clumping habit. The wrinkled leaves and thorny branches on Japanese rose are characteristic of this variety of rose. Japanese roses grow best in full sun to part shade and well-drained, nutrient-rich soils. They are suitable in USDA zones 3 to 9.
Hellebore (Helleborus odorus "Double Queen") is a winter-blooming, evergreen, perennial flower with double blooms. They grow up to 3 feet tall and wide and have a moderate growth rate. Hardy, hellebore "Double Queen" is tolerant of frost and blooms among below-freezing temperatures. As an evergreen, the bright green, leatherlike foliage on hellebore retains its color year-round to provide a burst of warmth to the garden. The blooms on hellebore "Double Queen" are pale to deep pink and white with a contrasting yellow center. They grow best in full to part shade and well-drained, nutrient-rich soils that are neutral to alkaline. To promote new growth on a hellebore, cut back the stems once the plant has bloomed. Hellebore "Double Queen" grows best in USDA zones 4 to 9.