The genus Hydrangea is expansive and includes approximately 1,000 species, hybrids, and cultivars, which can be deciduous or evergreen shrubs up to 10 ft tall, small trees or climbers reaching up to 98 ft. They are native to Asia and the Americas, with the greatest species diversity in eastern Asia, notably Korea, China, and Japan. Hydrangeas are popular ornamental plants due to their interesting large, showy flowers with different colors and inflorescence forms. Many hydrangea species are often used to design landscapes and gardens. The blooms vary in color, which can be white, green, purple, red, blue, or pink. Flower forms include mophead, lacecap, and cone-shaped blooms. There are 5 main types of hydrangeas in North America: bigleaf hydrangeas (Hydrangea macrophylla), panicle hydrangeas (H. paniculata), smooth hydrangeas (H. arborescens), oakleaf hydrangeas (H. quercifolia), and climbing hydrangeas (H. petiolaris). Two of the main types of hydrangea are native to the United States: smooth hydrangea, which is also known as “wild hydrangea”, and oakleaf hydrangea. However, the most common type in the US is the bigleaf hydrangea (H. macrophylla).
Hydrangeas commonly produced commercially in the United States are deciduous shrubs, selected for their showy flowers. They are the second most popular deciduous shrubs in the U.S. and are produced in more than 1,500 nurseries nationwide. They are grown in containers or in the field. Well-drained container substrate is recommended. For field planting, well-drained, moist soil, preferably a fertile sandy or silt loam with greater than 1 percent organic matter, is recommended. Typically, a medium to high rate of ‘Controlled Release Fertilizer’ is incorporated or top-dressed, applied to the surface of the substrate at the time of planting and again the following summer, depending on the production cycle and fertilizer longevity. For field production, a typical recommendation for all shrubs is no more than 50 pounds of actual N per acre (agricultural-grade nitrogen) applied in the spring when soil temperatures maintain higher than 50 F consistently and again approximately 3 to 5 months later. Hydrangeas are considered high water users, so timely irrigation practices are essential for both container and field-grown crops. Monitor irrigation (frequency and volume) for many benefits: to improve growth and plant quality, control plant size for shipping, reduce leaching, and limit root rot outbreaks. Plant growth regulators are typically used to induce branching or reduced growth in nursery crops.
According to the USDA NASS Census of Horticulture 2014, hydrangeas in the US have a wholesale value of $121M and are the highest in terms of units (deciduous shrubs) sold with more than 10 million plants being sold annually for $91,265,000, accounting for 13.5 percent of annual US shrub sales.
Main Disease Problems
Hydrangeas have a wide variety of disease problems including anthracnose, Botrytis leaf and flower blight, leaf spots, root rots (Armillaria spp., Polyporus spp., Rhizoctonia spp., Sclerotium spp., Phytophthora spp., and Pythium spp.), powdery mildew, rust, virus diseases (alfalfa mosaic, cucumber mosaic, hydrangea mosaic, hydrangea ring-spot, tobacco rattle, tobacco ring-spot, tobacco necrosis, tomato ring-spot, and tomato spotted-wilt viruses), and nematodes (leaf, lesion, root-knot, and stem nematodes).
Main Pest Problems
Hydrangeas have several pests such as aphids, black vine weevil, foliage-feeding caterpillars, four-lined plant bug, Japanese beetles, plant bugs, rose-chafer, scales, spider mites, thrips, and whiteflies. Slugs and snails can be damaging also.
Most of the research IR-4 has sponsored has been related to crop safety (350 trials with 87 products), and in nearly 200 trials we have screened new actives and products with Hydrangeas for effective management of Botrytis blight, Fusarium oxysporum, Pseudomonas chicorii, Pseudomonas marginalis, red-headed flea beetle, liverwort, nutsedge, oxalis, and PGR effects.
USDA-NASS Census of Horticulture, 2014
Ely Vea, IR-4 Environmental Horticulture Program Assistant Manager, Jackie Cavaliere, IR-4 Environmental Horticulture Program Coordinator, and Cristi Palmer, IR-4 Environmental Horticulture Program Manager