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Hydrangeas
Hydrangeas have been a garden favorite in Arkansas for many years. They produce large showy pink or blue flowers are gracing many landscapes. Not all hydrangeas are the same. Flower color varies by species, with some white, pink or blue, some even green. Some will tolerate more sun than others, and pruning needs vary by species. With increasing popularity, and new varieties emerging every season, there should be a hydrangea for almost every landscape. Choosing the right hydrangea for your yard can be a daunting task. There are 23 species of hydrangeas, but five that are commonly available and commonly grown. The most common hydrangea grown in our gardens is Hydrangea macrophylla—the big leaf hydrangea. This hydrangea is the one that produces the large pink or blue flowers (depending on pH of the soil) in either mophead form or lacecap form. Acidic soils produce blue flowers, while alkaline soils produce pink. Aluminum sulfate fertilizer will keep them blue, while lime will make them pink. In the neutral zone we have purple blooms. Another common hydrangea for woodland gardens is the Oakleaf hydrangea, Hydrangea quercifolia. This plant has large oak-shaped leaves and panicles of white flowers in early summer, which fade to dusty rose and then tan. In addition to spectacular flowers, the leaves turn brilliant shades of red in the fall landscape. The old-fashioned ‘Annabelle’ hydrangea is one of the smooth hydrangeas, Hydrangea arborescens. Most smooth hydrangeas have white flowers that bloom on the new growth and ‘Annabelle’ blooms are fairly large and showy. A new introduction ‘Invincibelle Spirit’ produces large pink flowers. Support for the stems is sometimes needed to hold the large flower heads. Another old fashioned white bloomer is the panicle or PeeGee hydrangea, Hydrangea paniculata. These plants can grow quite large and are often tree-formed. Like the smooth hydrangea, they bloom on the new growth. ‘Pink Diamond’ will take full sun and the ‘Limelight’ form has greenish white blossoms. Of the hydrangeas, panicle forms will take the most sunlight. And last, but not least is the climbing hydrangea—a totally different form of plant. Hydrangea anomala is a vine that can grow in deep shade and still bloom. While it can be slow to get established and start blooming, once it does, the lovely white flowers are quite showy. All members of the hydrangea family like a rich soil with plenty of moisture. Except for the climbing hydrangea, they need some sunlight in order to set flowers. Full morning sun or filtered sun with protection from the hot afternoon sun is best for most; however, the H. paniculata ‘Pink Diamond’ can grow in full sun. Direct afternoon sun on the big leaf hydrangea will give you a wilted plant every afternoon regardless of how much water they have. Hydrangeas are not drought tolerant plants, needing ample moisture to thrive. Fertilize with a slow release fertilizer in early spring after all frost has ended. A light application following the first flush of flowers can also be used. The season of pruning is not the same for all hydrangeas. Some plants bloom on the new growth—Hydrangea paniculata and H. arborescens, so can be pruned before growth begins in early spring or as they are going dormant in the fall. I prefer to prune before new growth so there is at least some structure in the winter garden. Hydrangea macrophylla and H. quercifolia bloom on the old growth, so should be pruned immediately after flowering if needed. Hydrangea macrophylla typically blooms in early summer. It sets its flower buds for the next season on the old wood, after it blooms, in late summer to early fall as the days get shorter and temperatures cool off. The ideal time to prune—if needed, is immediately as the flowers begin to fade. Try to have all pruning done by August. The later they are pruned the smaller your flowers will be the next season. Often the earlier you get it done after bloom, the quicker the recovery and the more blooms next season. There are a few varieties of H. macrophylla that are remontant – which means they are capable of having more than one bloom cycle. Two of the varieties getting a lot of press now are ‘Endless Summer’ and ‘Blushing Bride.’ These H. macrophylla will bloom throughout the summer, and will bloom on new growth even if the old growth is winter damaged. For remontant types, deadhead the spent flowers throughout the growing season, just like you would your perennial flowers. This will encourage them to set more flowers. They actually bloom on both the old and the new wood. Try to plant your hydrangeas in a location where maximum size can be utilized, and this can cut down on your pruning chores. When they do need pruning, remove up to one third of the old canes at the soil line either after the first bloom or before growth begins in the spring. Some gardeners prune a few canes each season, while others wait until the plants have overgrown their location, or when the flowers become smaller and less showy. If the plant gets old and woody, it can often produce smaller blooms. Since hydrangeas produce multiple trunks or canes, pruning cuts should remove canes at the soil line. Top-pruning hydrangea canes, will result in branching. On Annabelles and PeeGee hydrangeas that works, but H. macrophylla produces large terminal flower buds on the end of each branch and multi-stalked canes can bend over under the weight of multiple flowers. When pruning big leaf hydrangeas, cut the older canes out as close to the soil line as possible. This should reduce the overall size and height of the plant, while leaving ample remaining stems for showy blooms the next season. Keep in mind that most hydrangeas are not the most attractive plants in the winter. They usually look like a bunch of dead sticks—so don’t have them in the most prominent part of your winter landscape. Some gardeners erroneously think their big leaf hydrangeas are dead sticks, and prune them to the ground each winter. They rarely see a flower on their plants. Protect the plants as much as possible in the winter. H. macrophylla, the big leaf hydrangea tends to be one of the first plants to begin growing, often in the dead of winter. If the terminal bud begins to sprout, (which often happens when we have a warm spell in the winter), a following hard freeze can kill the bud. When this happens, there are usually smaller flower buds further down on the stem which can take their place and bloom in the summer. The flowers produced from these smaller buds will not be as large and showy as those from a terminal bud, but they are still quite nice. If there is a really hard winter, the entire bigleaf hydrangea plant can be killed to the ground. The plant will re-grow from the root system, but you will usually have few, if any, blooms that growing season, unless you are growing the reblooming types like ‘Endless Summer’ and ‘Blushing Bride.’ Oakleaf hydrangeas tend to stay dormant longer and rarely have any winter injury. They also can be somewhat attractive during the winter, with their shaggy, peeling bark. Smooth and panicle hydrangeas are usually immune to winter damage, and even if it occurs, since they bloom on the new growth, they still will bloom this growing season. Deadheading is a process where spent flowers are removed. There are several schools of thought about this. Some gardeners like the look of the dried blooms on their plants, and even consider it an extra form of winter protection for their flower buds. They clip off the spent blooms as the buds begin to emerge in the spring. Others find the spent flowers an eyesore and remove them as the flower color fades. Either option is fine, just be careful about how much stem is cut when you do deadhead. The earlier you prune them off, the longer the stem can be. The later you deadhead, make sure you are simply just removing the flower head with very little stem. You don’t want to damage any flower buds which may have already formed. Hydrangea quercifolia, the oak leaf hydrangea usually doesn’t require as much pruning, provided it has ample room to grow. If pruning is needed, follow the same guidelines as for H. macrophylla. Hydrangea paniculata (panicle hydrangea) and H. arborescens (smooth hydrangea) require a totally different method of pruning and are both much more forgiving if pruning is not done at a certain time. Other than pruning when flower buds are opening, you really can’t mess these up too easily. The panicle (PeeGee) hydrangea can be formed into a tree, with very little pruning other than shaping done each year before growth begins in the spring. It can be pruned hard if needed, but do so before it begins to leaf out in the spring. H. arborescens or the smooth hydrangea (Annabelle) may or may not be pruned hard before growth begins. The smooth hydrangea will produce much larger blooms if pruned hard each year, but many gardeners opt for smaller blooms on sturdier stems. Annabelle’s branches often fall over under the weight of their blooms, especially after irrigation or a good rain. Pruning crossover branches and pruning for structure and support by cutting stems to a heading of 18 – 24 inches can give you a sturdier branch to support the blooms, but even then you may need some additional plant supports to keep the branches upright. Today nurseries and garden centers carry a wide array of hydrangeas. Make sure you choose a variety that will suit your landscape needs, as well as the site. Most of them like some water, and most prefer a little protection from the hot afternoon sun—especially in the south, but there are exceptions to every rule. With good choices, and correct timing with pruning, your hydrangeas can stop traffic every year when in bloom. Additional Resources |
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