Although red roses and hydrangea are seemingly extremely different plants, they actually have quite a bit in common. Hydrangea and roses both can produce blooms from spring into the early fall months. These two plants are sometimes paired together in floral centerpieces and wedding bouquets. Both produce pink blooms because both plants contain a chemical pigment that produces red and pink hues. Both plants thrive in acidic soil.
While there are species of roses that grow across the world and in every climate, hydrangeas are a species that is native to Japan. There, both rose hips and the serrata species of hydrangea were blended into herbal tea. In the 1730s, the hydrangea was brought from Japan to England, where it and the rose both became emblematic of the formal English garden.
Both roses and hydrangeas derive their characteristic pink and red colors from a pigment known as anthocyanin. Anthocyanins are the substances that give berries their red, pink and blue colors and are present in red autumn leaves. In roses, anthocyanins are the reason that new growth at the tips of stems and the ends of canes appears red tinged. The concentration of anthocyanin is what determines the hue of the rose bloom. Certain varieties are characteristically prone to contain certain amounts of anthocyanin.
The color of anthocyanins is also dependent on the pH present in the plant. The pH rating determines whether the anthocyanin is pink or blue. This is in part why a hydrangea bloom may appear pink in highly acidic soil and blue or purple in alkaline soil. It is much easier to change a hydrangea from pink to blue than it is to change it from blue to pink. You can accomplish the former by adding aluminum to the soil, but the latter requires either taking aluminum out of the soil or raising the pH to the point that the hydrangea can't extract aluminum from the soil.
Roses and hydrangeas are cared for in a similar fashion. Both plants should have spent blossoms removed in order to promote new blooms. These old flower heads should be cut back to the first healthy bud. Old and dead rose and hydrangea canes should be removed, and the plants should be thinned to promote air circulation. All weak and spindly growth should also be removed so the plants put all of their energy into strong, healthy canes.
Rose and hydrangea blossoms can be dried and used together in arts and crafts. Rose blossoms can be dried by hanging them upside down in a dark location; this will help prevent fading and cause the rose to dry with a straight neck. Hydrangeas should be allowed to dry on the plant a little before air drying. Fresh hydrangeas will not dry well. If hydrangea stems are thin and weak, the plant should be hung upside down to dry with roses. Otherwise, hydrangeas can be dried upright.