How to Care for Limelight Hydrangeas
“Limelight” hydrangea (Hydrangea paniculata “Limelight”) lives up to its name as its show-stopping, elongated midsummer flower clusters open lime-green, brighten to white and assume hints of rich pink in fall. The 6- to 12-inch blossoms earned the Association of Specialty Flower Growers’ award as the 2007 Cut Flowers of the Year. The debut from Dutch nurseryman Pieter Zwijnenburg, Jr. grows as a 6- to 8-foot, curved, deciduous shrub in U.S. Department of Agriculture plant hardiness zones 3 through 9. With the removal of its lower branches, “Limelight” produces a stunning small tree.
Plant “Limelight” to a site with organically rich, well-drained loam. Enhance the site, if needed, by spading a 2- to 4-inch layer of organic material such as compost or peat moss into the top 8 inches of soil. “Limelight” is happiest in morning sun and afternoon shade, and suffers in warm, dry places. Shrubs planted in fall gain from cooler temperatures and winter rains because their origins establish.
Water “Limelight” slowly and deeply to encourage deep root creation. While panicle hydrangeas are more drought-tolerant than their relatives, they still lose substantial moisture during their large, dense leaves. Watering weekly for 20 minutes with a soaker hose or drip system ensures maximum water consumption.
Feed “Limelight” twice yearly in April and June with 10-10-10, general-purpose slow-release fertilizer. After applying the fertilizer in the manufacturer’s specified rate, then water the plant in order that the fertilizer penetrates the soil.
Watch the shrub for signs of leaf-damaging insects, such as aphids, whiteflies and scale insects. Look for a clear, sticky waste and dark sooty mold on the leaves and branches, both indications of aphid or whitefly infestation. Scale insects resemble colonies of miniature barnacles clustered on the bark. Releasing the pest’s natural predators, such as ladybugs, to your own garden, manages them naturally. Spraying the shrub with insecticidal soap, according to the tag’s specifications, controls serious infestations.
Assess for leaf diseases, such as powdery mildew, rust and leaf spot. Powdery mildew causes white to grey, talclike coating on the leaf. Leaf spot fungi leave yellow or yellowish brown patches while rust surfaces as raised, reddish or yellow pustules on the leaf surfaces. Prune and destroy the infected foliage, and clean up fallen infected debris to prevent additional leaf spot or rust contamination. Treat heavy powdery mildew infection with olive oil spray.
Prune “Limelight” before its new growth emerges in late winter or early spring to damaged, dead, diseased or crossing branches. Since “Limelight” flowers on new wood, pruning in spring to shape the plant will not diminish its flower display.