There are over 70 species of hydrangea and over 600 named cultivars native to Asia and North America. Depending on species, they can flower from spring to autumn producing either corymbs or panicles on the terminal ends of the stem. The flowers produced are often small and non-showy in the center or interior and develop large showy sepals to the exterior of the flower.
There are many hydrangea - H. macrophylla (mophead or pom pom), lace caps (flat flower with a center of smaller flowers surrounded by much larger), paniculate (white panicle flowers in late summer) quercifolia (Oakleaf) and serrata (mountain types). All have multiple varieties offering size, color, and other variations.
Hydrangea macrophylla one of the most sought-after species develops large pom pom flowers or lace cap flowers in colors of blue, red, pink, light purple, and dark purple. The aluminum ions in the soil are tied up due to the pH of the soil. If the soil is acidic or a pH below 7 the plants will usually develop flowers in the blue to purple range and if above pH 7 or alkaline the flowers will be in the pink to red range. You can adjust this by applying the proper fertilizer but you must apply this prior to flower development. This deciduous variety prefers protection from the hot afternoon sun, and a moist organic loamy soil. They can scorch in the hot afternoon sun. They are also prone to develop leaf spot in high humidity so never water from the top only at the soil level. Prune immediately after flowering as they produce buds on old wood. Flowers are sterile and of no real use to pollinators.
Hydrangea paniculata has many varieties ranging from 3 ft x 3 ft to over 15 feet by the same. This deciduous plant has smaller leaves and can tolerate more sun. Blooms start to develop in mid - summer and are chartreuse to start turning white then developing a pink to maroon hue. They require a moist organic well-draining soil and offer a more even flower if placed in a full sun rotational location. Prune in early March as they bloom on new wood. Flowers offer little to pollinators.
Hydrangea quercifolia is native to our area. The leaves resemble an oak tree and this deciduous plant does best in dappled shade to part shade. The hot afternoon sun can cause scorch on the leaves. Flowers are panicle and creamy white. This plant offers pollen and nectar to pollinators but is only available from the smaller flowers located in the inner portion of the panicle. They develop a wonderful maroon color in the fall. Prune immediately after flowering as they produce on old wood.
Hydrangea petiolaris, or climbing hydrangea are wonderful deciduous part shade vines that can climb to 15 feet tall by 10 feet wide. They offer shiny ovate leaves, corymbs of creamy white flowers and stems that exfoliate to a dark cinnamon brown for winter interest. Moist organic soils keep this slow grower happy.
Hydrangea serrata or mountain hydrangea is a very hardy plant that offers bloom even after colder winters. These deciduous plants are smaller shrubs than many of the others with leaves that turn maroon in the fall. Flowers depending on variety can be pink to maroon or blue to purple. Plant in part shade to shade. Moist organic soils work best.
When planting a landscape keep hydrangeas in mind as they offer wonderful flowers, are reliable as foundation plants or specimens, and need minimal pruning if right the plant is in the right place.