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Mendocino Coast Botanical Gardens, 47 acres of botanical bliss fronting the Pacific Ocean

Hydrangeas

Colorful shrubs for the home garden!

Botanical Name: Hydrangea spp. Common Name: Hydrangea Family: Hydrangeaceae 

Description: Hydrangeas are deciduous shrubs or vines. Most species can be successfully grown in Zone 17, if protected from frost. These showy plants are a wonderful background choice in a mixed bed with perennials and annuals. They are dormant during the winter months.

Other important facts about Hydrangeas: Hydrangeas do well in full sun on coast or partial shade inland, blooming in summer and fall. The flowers can be dried if picked before fading. The flowers can be white, pink, red or (under acid soil conditions) blue. Some flower clusters may contain sterile or fertile flowers, and the biggest flower clusters can be encouraged by reducing number of stems. Hydrangeas can be showy as single plants, massed or in tubs.

Cultivars: Selections that thrive in North Coast Region (Sunset Zone #17): H. anomala petiolaris – climbing hydrangea – From Russia, Korea, Japan. Climbs high (up to 60 ft.). Becomes woody with age. White lace cap flower clusters. Heavy pruning can rejuvenate in late dormant season. H. arborescens – smooth hydrangea – Native from New York to Iowa, Florida and Louisiana.Upright shrub to 10 ft. tall and as wide. Several cultivars are very showy with white dome-shaped flower clusters. Prune in late dormant season. H. aspera – Imposing shrub to 10-12 feet. Spreads as wide. To improve form, cut back hard for first 3 years. Flowering will be delayed. H. paniculata (Variety 'Grandiflora') – Native to Japan and China. Upright 10-20 ft. Flower clusters can reach 1 ½ feet. Newer varieties include 'Burgundy Lace' 'Ruby' and 'Tardiva.' H. quercifolia – oakleaf hydrangea – From southeastern U.S. Does very well on the North Coast. Grows up to 6 ft tall and 8 feet wide. Handsome, deeply lobed, 8 inches long leaves that resemble those of oaks. They turn bronze or crimson in fall.

Cultivation: Hydrangeas need rich, loose, well-draining porous soil that has been amended with well-aged compost. They require very light fertilizing. If soil is rich in organic material, fertilize lightly only in the spring. Protect from heavy frost by mounding soil or leaves over base of plants. They need regular watering; do not let plant dry out. (Flowering will be sparse in heavily shaded areas.) Many cultivars maintain a pink or blue color if in alkaline soil (Ph 6.0-6.5) To assure blue flowers, apply lime or aluminum sulfate to soil at start of bloom. Prune heavily in frost-prone areas immediately after flowering.

Propagation: Take cutting from branch 5-6" that did not flower last year. Remove lower leaves of bottom two nodes. Cut largest leaves to half size. Dip cuttings in rooting hormone (optional) and insert into damp vermiculite. Water pot well and let drain. Cover cutting and pot with plastic that is staked so it does not touch leaves. Place cutting in bright light but not in the sun. Do not water until top of soil is slightly dry. Cuttings will form roots in 2-3 weeks. Cutting is rooted if resists tugging.

Submitted by Master Gardener Becky Ellis, 2007.