Selecting And Caring For Hydrangea Trees
Technically there are no such things as hydrangea trees, though you may see certain varieties advertised as such. There are five species of hydrangea cultivated in the United States, with only one of the species capable of taking on the shape of a reasonably large tree. One other species will climb to significant heights, given proper support. The five varieties are the Smooth hydrangea, which includes the cultivar "Annabelle", a very popular variety found in many gardens. Another species, also very popular, is the Bigleaf hydrangea, sometimes called the French hydrangea The Oakleaf hydrangea, native to the southern United States is yet another species, whose blossoms often last into the winter months.
Almost A Tree - The fourth type, though not a tree, is the Climbing hydrangea. This hydrangea is a true vining plant, which will grow up to 60 feet high, but requires very sturdy support to allow this to happen. Because of its sticky tendrils, it's not a good idea to grow this hydrangea up against a house or any other structure whose surface you don't want to deface. A dead snag would provide the ideal support for this hydrangea, and the net result would be a climber having a definite tree-like appearance.
The Pee Gee - This brings us to the fifth species, the Panicle hydrangea (H. paniculata). This hydrangea is more popularly known as the Pee Gee hydrangea, and is the tallest of the free standing species, attaining a height of 20 feet. If left alone, the Panicle hydrangea will take on the form of a large shrub, but tolerates pruning very well, and can be pruned to a tree-like shape. Thus in the Panicle, or Pee Gee, we have the species that provides us with hydrangea trees. The Pee Gee is also the most cold hardy of the 5 species and does well in USDA zones 4 to 7 (some claim its range to be zones 3 to 8). The name Pee Gee originally applied only to the cultivar "Grandiflora", but over time has been used for other of the Panicle cultivars. Panicle, or paniculata, comes from the shape of the leaves, which are somewhat cone shaped (panicle shaped), whereas the leaves of most hydrangea species are more ball shaped. “Limelight" may well be the most popular cultivar of the Panicle hydrangeas, as it does well in all parts of the United States, with the exception of the extreme southern region, and is a favorite in southern Canada as well.
The Pee Gee's flowers bloom on the current year's growth, so late summer or fall pruning is best, and can be done without danger of adversely affecting the following year's bloom. Care is much the same as with the other hydrangea species, one exception being that hydrangea trees prefer more direct sun, whereas many hydrangeas do well in partial shade, though not in deep shade. Hydrangeas often do poorly if planted too near a tree, which one would not want to do in the case of hydrangea trees in any event. The one exception to this might be the climbing hydrangea
Planting Hydrangea Trees - Hydrangeas should be planted in a well drained soil which is not too heavy. The degree of acidity in the soil may affect the color of the blooms, with blue blooms produced by an acid soil, and pinkish blooms produced when the soil is alkaline. Lime can be added to the soil to ensure the blooms will be on the pink side, or apply a dressing of aluminum sulfate if blue blossoms are your goal. Many times hydrangeas are purchased in a pot, ready for transplanting. A good idea is to purchase a plant that is in bloom so you'll know what color to expect. There are so many cultivars on the market that it's easy to get them, and the resulting colors, mixed up.
Fall is the best time to plant, as if the hydrangea is becoming dormant it only requires a single watering until new growth begins to appear. If transplanted in the summer months though, regular watering will be needed. Most hydrangea varieties are fertilized twice during the summer months, and never after blooming has ceased. Hydrangea trees may need a greater amount of fertilizer given their size, but most plants do fine when a little compost or manure is mixed in with the soil. Chemical fertilizers are not an absolute requirement.