Long-lived shrubs with a punch of color!
Hydrangeas are shrubs with handsome foliage and big beautiful summer blooms. They thrive in the shade, brightening the garden with blue, pink, white or lime-green flowers. One plant makes an outstanding specimen, a row makes a flowering hedge. For small gardens there are dwarf and container varieties, compact but retaining the big blooms. All hydrangeas bloom in the summer, with many selections of newer varieties that will rebloom long into the season. For a fall bonus the leaves turn copper, orange and pink, a last dash of color for the landscape.
Types of Hydrangeas
There are many types of hydrangeas with different bloom types and leaf shapes. The most familiar is mophead type with big balls of bloom. These are also known as bigleaf hydrangeas and smooth hydrangeas for their broad leaves. They are often grown in small pots for florist flowers, but there are many that are terrific garden plants. Here in Denver look for winter-hardy varieties like Annabelle and Incrediball, and the Endless Summer and City Line series. City Line Paris is a pink-flowered compact variety, about 3 feet, ideal for patio containers.
Airy lacecap flowers are flat and loose, with a tight central cluster of small starry flowers surrounded by larger open-faced sterile flowers. The flower clusters can be very large and make a great show in the shade. To brighten up shady spots even more, choose a variety with white-marbled leaves.
Oakleaf and panicle hydrangeas have large lobed leaves and tall cone-shaped clusters of flowers, usually white or greenish. They overwinter very well in the Denver area, making large shrubs with interesting peeling bark as they mature. For additional color pick Hydrangea Quick Fire. The bloom starts white and turns pink. Again, compact varieties are available if space is limited.
Hydrangeas can be grown in a range of sun and shade conditions. Be sure there is enough sun for blooming! Too much shade will reduce flowering. Hydrangeas need moist well-drained soils, rich in organic matter. Most Colorado soils will benefit from the addition of peat moss and compost, retaining moisture as well as acidifying the soil. A layer of mulch is also helpful to keep soils evenly moist. After planting check frequently and water as needed. Water well for the first year or two until well established. Remember to water once a month through the winter too to prevent winter kill.
Photo right: Proven Winners
One of the fascinating things about hydrangeas is how they respond to soil chemistry. Acidic soils will produce blue flowers and alkaline soils produce pink flowers in many varieties. The soil acidity balance changes the availability of aluminum compounds that create the flower colors. Soil amendments, like peat moss for blue, and other soil treatments are available to control the color. Not all varieties respond to the soil treatments so ask for color recommendations from City Floral’s experts.
Winter hardiness for hydrangeas has two aspects. Flower buds are often more tender that leaf buds, so hydrangeas sometimes are damaged if hard frost hits when the flower buds are vulnerable. The plants will leaf out and grow well, but there are no flowers.
Another factor in hydrangeas is where the flower buds form. Some types produce the buds on branches in the fall and overwinter to bloom in the spring. They are said to bloom on old wood. An early hard frost in the fall can kill the flower buds. Bigleaf and oakleaf varieties produce on old wood. Fall pruning that removes the old wood on these varieties will remove the flower buds too. Wait until after blooming in the spring for pruning.
Other hydrangeas, including the smooth and panicle hydrangeas, bloom on new wood, branches that have grown this blooming season. This group can be damaged by late spring frosts as the buds are breaking dormancy. Watch the weather and cover the plants to protect the bloom. This group can be pruned in the fall since it will produce flowering new wood in the spring.
New hydrangea hybrids and cultivars are being selected for increased fall and spring hardiness. Compact varieties, since they grow smaller, reduce the need to prune. For maximum flowering, be sure to ask about pruning recommendations for the varieties you have selected. Come next summer you will be thrilled with the results.