May is a beautiful time at Gibbs Gardens. This year, the selection of mock orange, Philadelphus ‘Natchez,’ was spectacular. The flowers are fragrant with a scent that reminds some of sweet orange. This sturdy shrub has a fountain-shaped habit and can easily reach 8 to 10 feet or taller. In late spring, it is covered with large white blooms, 1 ½ inches wide, that look similar to dogwood flowers, hence one of the other common names, English Dogwood.
Currently the roses are blooming with enthusiasm. They provide great sweeps of color in red, pink, white and yellow throughout the gardens. Jim says that the knockout series is great because even if you don’t dead head (remove spent blossoms), they will flower for months. As far as feeding roses, he recommends applying a small amount of a slow release fertilizer in early spring, usually in March, and then again in June and early September. While a general all-purpose fertilizer will do the trick, some rose growers create their own special mix formulated for roses. One thing all roses like is plenty of water. With all the rain in April, the roses are very happy.
When it comes to pruning the knockout roses at Gibbs, here’s what Jim recommends. In March, they use a power hedge trimmer to remove all the spreading growth that occurred during the year and then follow up with hand pruners to make sharp, clean cuts, reducing the plants to a height of 12 to 18 inches. He notes that in Atlanta this can be done as early as mid-February.
Jim has found that with one severe pruning, the knockout roses will not require any additional pruning during the growing season, blooming on new spring, summer, and fall growth. If you are adding new rose plants to your garden, plant them on 5-foot centers. By fall, they will be full plants that touch one another.
Another favorite rose at Gibbs Gardens, for its vigor and pale pink, slightly fragrant flowers, is Rosa ‘New Dawn.’ This vigorous climber, a repeat bloomer, will easily grow 8 feet or taller. A wonderful display, it covers the arbor located below the Manor House. In another area of the Gardens, ‘New Dawn’ uses a Crepe myrtle as a living trellis. When you plant this rose in your own garden be sure to give it a large sturdy support.
Jim also likes the Drift series of roses, which are smaller and well suited for groundcovers. Low maintenance and disease resistant, they come in a wide range of colors.
Ferns abound in the gardens, providing not only myriad shades of green, but texture too. Some of my favorite native species include the evergreen Christmas fern, Polystichum acrostichoides, Cinnamon fern, Osmunda cinnamomea, New York fern, Thelypteris noveboracensis, and the Royal fern, Osmunda regalis.
Of the many types of hydrangeas that grow at Gibbs Gardens, the native oakleaf is blooming now and the Annabelle hydrangea, Hydrangea arborescens, also a native, will follow suit in the next few weeks.
In the sequence of bloom, the bigleaf hydrangeas, including both the mophead types and the more delicate looking lacecaps, bloom in June, July and August. However, this year they may not produce many blooms because the developing flower buds were killed by severe cold in early spring. Typically, H. macrophylla flowers on second-year wood, but some varieties like ‘Endless Summer’ produce flowers on new growth. To encourage more blooms, remove spent blossoms and provide plenty of moisture. Both this hydrangea and oakleaf hydrangeas require very little pruning.
In July and August, look for Hydrangea paniculata selections, also known as peegee hydrangeas. These bloom on new growth so you don’t have to worry about cutting them back. The best time to prune is in early spring right before new growth begins, but if plants are overgrown, you can cut them back in late spring and still expect lots of blooms. H.‘Limelight,’ popular for its flowers, which start out lime green and quickly turn white, is a prolific bloomer. I also like Hydrangea paniculata ‘Vanilla Strawberry’ with red stems and flowers that emerge white and turn pink and even strawberry red, especially with cooler night temperatures. Look for these in August behind the large tent near the Arbor Café.