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Garden Guide: The Endless Summer Hydrangea

The botanical name of the species to which the Endless Summer hydrangea belongs is Hydrangea macrophylla. This particular species is characterized by plants having larger than normal leaves for a hydrangea and blossoms that, for a number of varieties, are referred to as snowballs or mopheads. Its blossoms are unusually large, often attaining a size of 8 to 10 inches. The blossoms make excellent cut flowers and can be used in dried flower arrangements as well. A typical bush of this cultivar will grow to a height of approximately 5 feet and a width of 4 feet. It can be grown as a container plant.

One of Several Species and Many Varieties

There are over 20 different species of hydrangeas and over 500 different varieties of H. macrophylla in existence as well, including Endless Summer hydrangeas, of which several varieties exist and are on the market. Only two or three of the 20 or so species of hydrangeas are grown in the United States, one reason being that the large-leaved H. macrophylla species is by far the most popular species with gardeners. H. macrophylla hydrangeas are hardy to USDA Zone 6, with some sources claiming that the variety can be grown in Zone 4 as well. In any event, this plant appears to do best when grown in more temperate to cooler climates. The species is native to Japan.

What Is with the Name?

The name Endless Summer becomes obvious when you have a flowering plant in your garden that seems to bloom faithfully every summer no matter what, a characteristic that hydrangeas are not generally known for. This is of course the case with other shrubs and trees found in the average garden as well: plants that do not always bloom uniformly from year to year but often experience great blooming years as well as poor ones. Not only does this variety faithfully produce blooms every year, but also the blossoms that form usually last all summer and into the fall. When you have a plant that produces flowering buds in both the fall and the following spring, as is the case with this hydrangea cultivar, that is something that is bound to happen.

The vast majority of hydrangea species and varieties set their flower buds during the fall season, anytime between late August and mid-October. Endless Summer varieties are different in that they can set bloom buds in the spring as well as in the fall. This helps to ensure that if the buds that are set in the fall are pruned off or suffer damage due to the winter weather, a plant will still offer a healthy set of blooms the next summer. Looking from another perspective, the difference between this variety and others is that it is able to set buds on both new growth wood (spring) and old growth wood (fall), whereas other species and varieties only set buds on old growth wood.

Endless Summer is not the only variety with this particular characteristic. Other popular varieties are David Ramsey, Penny Mac, Decatur Blue, and Oak Hill. All of these varieties produce a profusion of pink or blue mophead blossoms year after year. Another name for the reblooming characteristic is remontant. As is the case with other types of hydrangeas, the color of the blossom is heavily influenced by the pH of the loam the hydrangea has been planted in.

Planting This Variety

As is the case with most hydrangeas, this variety of hydrangeas should be planted in a sunny location, although it will do best if planted in an area where it can get some afternoon shade. Planting these hydrangeas on the north side of your house might be a good idea since they are more likely to be shaded from the hot afternoon sun. Planting on the east side of the house might be an alternative. These hydrangeas can also be located on the edge of a woodland setting where they will get some shade from tall trees. While these varieties of hydrangea will grow in deep shade, they are not apt to produce much in the way of flowers.

Well-drained soil is a must. The best results will be obtained if the earth is kept somewhat moist. When preparing the soil, it is recommended that compost be added to the top foot or so of the earth in the immediate area. The more compost, the better; 50 pounds of compost mixed in with soil covering a 10-square-foot area is not too much. Organic compost not only provides nutrients but also helps to keep the ground moist around the roots of the plants during summer dry spells. Insofar as treating the soil in such a way that it will give you the color you are looking for in the blossoms, it’s best to wait until your hydrangea has become well established, which can take up to two months, before attempting to make the earth more acid (for blue flowers) or more alkaline (for pink flowers).

Choosing Your Color Preference

While the pH of the soil plays a determining factor as far as bloom color is concerned, the presence or absence of aluminum in the soil can play an even greater role. What the pH largely accomplishes is to determine how efficiently aluminum present can be absorbed by the roots. Mixing sulfur with the surrounding soil – again after the hydrangea has become established – is another way to obtain blue blossoms, while doing the same with dolomite lime will cause the blossoms to be pink. These color changes do not happen overnight, and in fact, the change may not become noticeable until a year or so has passed. Drenching the soil with a solution of aluminum sulfate or dolomite lime can sometimes hasten the desired result.

One of the most significant advantages of growing hydrangea varieties is that the plants can be pruned back severely in frigid climates to avoid winter damage to the branches or the foliage. When this is practiced with most varieties of hydrangeas, the inevitable result will be a healthy plant every summer, but one that is rich in foliage but has few – if any – blossoms because the buds have been pruned off. Damage is most likely to occur in climates that feature sudden cold snaps during the spring – not so with this cultivar, although an unusually late cold snap in the spring could cause bud damage.

Pruning Anytime of the Year – Almost

Most species and varieties of hydrangeas are pruned following the summer blooming period. This allows the old flowering heads to be removed before new buds would be developed. Pruning can be done in the winter to remove interior branches and better control the shape of all plants as long as care is taken not to remove too many of the buds that form in the fall. The same pruning practice can apply to Endless Summer, except that this is a variety that can be pruned at almost any time of the year, although pruning during the spring is not recommended. As noted previously, it can be pruned back to the ground in the late fall and will still bloom the following summer.

If you do not need to prune your plants back to the ground every year or choose not to do so, it is still a good idea to prune up to a third of the older stems back to the ground on occasion. This would only need to be done after a flowering plant has become at least 5 years old or older. This is not a requirement, but doing so would tend to revitalize the plants.

If you remove the blooms as they start to fade (deadheading), you can prune the stems back further. If you wait too long, new buds will start to form closer to the spent blooms and you will then need to prune much closer to the spent blooms. This is not so important with the Endless Summer variety and is only important if you feel the need to retain a number of the buds that form during the late summer and in the fall.

Insects and Diseases

Hydrangeas in general are relatively pest-free plants. Pests that do tend to make themselves present, such as mites and aphids, are generally easy to control. Aphids are most often apt to infest relatively young plants and are seldom a problem once a flowering plant has become established. If aphids should appear, they can easily be washed off. Mites can sometimes be a problem and can be more difficult to control. The best way to deal with mites is to take preventive measures, which primarily involve making certain the plants are being supplied with sufficient moisture during hot spells.

Powdery mildew is a disease most likely to affect the Endless Summer variety and is the most common disease affecting other members of the H. macrophylla species. Powdery mildew rarely does much damage but it can of course make your hydrangeas unattractive until it has run its course. Leaf spots caused by fungi are another disease that does minimal damage to the plant but can cause it to become less attractive.

Another condition that can affect your plant is iron chlorosis. This is a condition that occurs in high-pH soils where iron tends to be less available. Iron chlorosis can cause newer leaves to take on a yellowish hue. This condition can be corrected by adding a chelated iron product to the loam, a practice that may need to periodically be repeated. Iron chlorosis is less likely to become a problem if aluminum sulfate has previously been added to the soil. If yellowing should occur on the older leaves, the reason is generally that of a nitrogen deficiency.


This kind of hydrangea does not set seeds as it is a hybrid and the flowers are sterile. In cases where a certain plant does set seeds, plants that sprout from seed will not come true. They can however be propagated using several different methods. Propagation can be accomplished using either herbaceous or woody stem cuttings. Softwood cuttings can also be used, as can hardwood or semi-hardwood cuttings.