Hydrangea
For beautiful and continuous blooms in Summer and Fall, nothing beats Hydrangeas. The long-blooming flower clusters of Hydrangea shrubs come in a variety of interesting shapes , sizes and flower color. While many are perfect for that shady area of your garden, there are also hydrangeas that perform well in the sun. If I could only have one variety of flowering shrub in my yard it would definitely be Hydrangeas.
Bigleaf, Mountain, Oakleaf, and Climbing hydrangeas flower on old wood (growth created in the previous season). Flower buds on these hydrangeas begin to form in late summer and must remain undisturbed all through the fall, winter, spring, in order to flower the following summer.
As a result, these plants will not flower if:
- They are pruned. Pruning at any time will remove potential flower buds.
- They are browsed by deer, which will eat the flower buds.
- They are damaged by weather. Winter weather isn’t actually the problem; rather, it is in spring, when several days of warm temperatures are followed by a sudden freeze, that flower buds are most likely to be damaged.
Reblooming Hydrangeas, also known as remontant hydrangeas, are types of big leaf and mountain hydrangeas that have the unique ability to flower on both old and new wood. Even if the buds are damaged in winter weather, the plant can still flower on wood it produces that season.
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Color
All hydrangeas undergo some color change as their flowers age, but only big-leaf and mountain hydrangeas can change their color in a predictable, controllable way. It is not the pH of the soil that is responsible for this change – it is actually the presence of aluminum in the soil that does it.
- Certain varieties of bigleaf hydrangeas cannot experience color change – generally speaking, the more intense the color, the less likely it can change (Cityline® Paris hydrangea is a good example). Similarly, white varieties of big-leaf hydrangea will not change color.
- It is easier to change a hydrangea from pink to blue than from blue to pink, but both endeavors involve making chemical application in specific amounts at specific times. A soil test is necessary to determine the best course of action. If you decide to try to change the flower color, shop for products carefully and read all directions.
- Pennies or nails in the soil will not change the flower color!
Pruning
- Avoid pruning reblooming hydrangeas and those that flower on old wood, altogether. Instead, site these hydrangeas appropriately so they do not need to be pruned, and choose varieties that do not get too big
for their space. - New-wood flowering hydrangeas can be pruned each early spring, just as the new growth begins to emerge.
Remove up to one-third of the height each year if desired to encourage vigorous new growth and strong stems to support the flowers. - Hydrangeas do not strictly require regular pruning. They will grow and flower well with nothing more than removal of spent flowers and any dead wood each early spring.
Fertilizing:
Hydrangeas do especially well when fertilizers are effectively used in spring or early summer. We recommend using a granular, slow-release fertilizer with a high percentage of phosphorus (the middle number in the NPK ratio). Phosphorus is the element that encourages bloom production. Follow the package instructions when applying fertilizer and be sure not to use too much. Over-fertilizing can cause hydrangeas to grow big green leaves, but stunt bloom production.