Hydrangeas are the beautiful backbone of summer flowering shrubs for many gardeners. However, hydrangeas do require a little bit of care and maintenance to reach their true potential. The most common forms of care and maintenance for hydrangeas include fertilization, pruning and overwintering protection.
Fertilizing and Flower Color
Most varieties of hydrangeas can produce a different color flower depending on the pH level of the soil in which they are planted. For varieties that do this, an acidic soil will cause the plant to flower a brilliant blue while an alkaline soil will produce magnificent pink flowers. Some varieties have been cultivated to be predisposed one way or the other, but for those varieties that have not, the gardener is in charge of this transformation. In order to get your desired flower color, you will need to fertilize the plant appropriately. Use a product like Miracid from Miracle-Gro or aluminum sulfate to fertilize for blue flowers. Granulated lime is the most popular option for gardeners who want to keep the flowers pink. Apart from applying fertilizer to control flower color, you should feed your hydrangeas sparingly. Too much nitrogen in the soil can have a detrimental effect on flower output. When fertilizing for general feeding purposes, use a balanced fertilizer like a 5-5-5 or a 10-10-10.
Incorrect pruning is one of the biggest reasons that hydrangeas fail to reach their potential. You should only prune the vine or big-leaf types of hydrangeas after flowering, if at all. If you have a paniculated variety (the flower forms a cone shape instead of a big ball), then you should aggressively prune them in the winter or very early in the spring. Otherwise, they will turn into uncontrollable monstrosities. However, there is one exception to this rule. In recent years, many nurseries have introduced new cultivars of hydrangea that bloom more than once in a season. If you own a variety that is a repeat bloomer (such as the Endless Summer Hydrangea from Monrovia), then you will want to prune the dead blossoms off over the course of the summer to encourage new blossoms. Prune the dead blossoms at the highest point possible to avoid pruning off the stem that contains the new blossoms.
For gardeners in colder climates, it is especially important to overwinter your hydrangeas properly. Late pruning, or too much pruning, can cause the hydrangea to flower poorly, or not flower at all, the next season. In addition, many horticulturists recommend that gardeners in colder climates insulate their hydrangeas to help them through the winter. You can accomplish this by taking leaves or mulch and mounding it around the plant in the fall. If you choose to insulate your hydrangeas this way, remember to remove the covering during the spring so that it does not have a negative impact on the hydrangea's development.