Exposure: For better and more blooms, give plants morning sun and light afternoon shade.
Soil: Make it rich and well drained. Add plenty of organic material at planting time. Don’t forget to mulch.
Pruning: Make cuts as needed to control form—late in dormant season for types blooming on new growth, after flowering for those blooming on previous year’s growth. For biggest flower clusters, reduce number of stems; for numerous medium-size clusters, keep more stems.
Big, bold leaves and large clusters of long-lasting flowers in white, pink, red, or blue. Bloom in late spring or summer. Flower clusters may contain sterile flowers (conspicuous, with large, petal-like sepals) or fertile flowers (small, starry petaled); or they may feature a cluster of small fertile flowers surrounded by ring of big sterile ones (these are called lace-cap hydrangeas). Sterile flowers last for a long time (often holding up for months), gradually fading in color. Hydrangeas are good looking as single plants, massed, or in tubs on the patio. Grow quickly and easily in rich, porous soil.
In some hydrangea selections, blue or pink flower color is affected by soil pH—bluest color is produced in strongly acid soils (below pH 5.5), pink or red in neutral to alkaline soils (pH 7.0 and higher). Florists control flower color of potted hydrangeas by controlling soil mix; blue-flowered florists’ plants may show pink blossoms when planted out in less acid soil. Flowers can be made (or kept) blue by applying aluminum sulfate to the soil, kept red (or pink) or made redder by liming the soil or applying superphosphate in quantity. Flower-color treatment is not effective unless started well ahead of bloom.
H. anomala petiolaris (H. petiolaris). CLIMBING HYDRANGEA. Deciduous vine. Zones US, MS, LS; 9–1. From Russia, Korea, Japan. Climbs high (as far as 60 ft.) by clinging aerial rootlets; shrubby and sprawling without support. Green, 2- to 4-in.-long leaves have a rounded heart shape. Mature plants develop short, flowering branches with flat, white, 6- to 10-in.-wide lace-cap flower clusters. Becomes woody with age. Prune out overly vigorous growth only after vine is well established and climbing. Can be rejuvenated by cutting back to framework late in dormant season.
H. arborescens. SMOOTH HYDRANGEA. Deciduous shrub. Zones US, MS, LS, CS; 9–1. Native from New York to Iowa, south to Florida, Louisiana. Upright, dense growth to 10 ft. tall and wide. Oval, grayish green, 4- to 8-in. leaves; white flowers. In basic species, most flowers in a cluster are fertile; the few sterile ones are not plentiful enough for full lace-cap effect. Much showier is ‘Annabelle’, which produces enormous (to 1-ft.) globular clusters of sterile flowers on a plant about 4 ft. tall and wide. ‘Grandiflora’ is another 4-footer; its flower clusters are 6 in. across. Prune in late winter. Hard pruning produces bigger flowers.
H. aspera. Deciduous shrub. Zones MS, LS; 9–7. From eastern Asia. Imposing shrub to 10–12 ft. tall, spreading nearly as wide. Dark green,
somewhat hairy leaves to 10 in. long, 4 in. wide. Rather flat, 10-in. flower clusters contain purplish white to pink fertile
flowers surrounded by 1-in. white, pink, or purple sterile blooms. Prune in late winter. To make a broad, many-stemmed plant,
cut back hard for first 3 years; flowering will be delayed, but plant form will be improved.
H. a. sargentiana (H. sargentiana) has broader, more heavily furred leaves. Fertile flowers are light purple; sterile outer ones are pinkish white, about 1 1/2 in. across.
Villosa Group (H. villosa) has blue or purple fertile flowers and
1-in.-wide, pale pinkish purple sterile flowers.
H. integrifolia. Evergreen vine. Zones MS, LS, CS; 9–6. From the Philippines, Taiwan. Rambling vine that climbs 25–30 ft. by clinging aerial rootlets. Somewhat similar to H. anomala petiolaris but has smaller, lance-shaped leaves and smaller flowers. Stems are red tinged and covered with fine hairs. Prune in winter.
H. macrophylla (H. hortensia, H. opuloides). FRENCH HYDRANGEA, BIGLEAF HYDRANGEA. Deciduous shrub. Zones US, MS, LS, CS; 9–3. From Japan. Symmetrical, rounded habit; grows to 4–8 ft. high (or more) and as wide. Thick, shiny, coarsely toothed leaves to 8 in. long; white, pink, red, or blue flowers in big clusters. Great performer in areas where winters are fairly mild; disappointing where plants freeze to ground every year (they may never bloom under these conditions, since flower buds are usually produced on old wood). Protect in colder zones by mounding soil or leaves over base of plants. Prune immediately after bloom.
There are hundreds of named selections, and plants may be sold under many names. Florists’ plants are usually French hybrids, shorter (1–3 ft. tall) and larger flowered than old garden types. Dozens of selections are sold; here are some of the best, including a couple of old favorites as well as some newer choices.
‘All Summer Beauty’. Unlike most other French hydrangeas, this one produces its dark blue or pinkish flower heads on current
season’s growth and blooms all summer. Prune late in dormant season.
‘Ayesha’. Heads of light purplish pink, cupped flowers (like tiny buttons).
‘Blue Wave’. Lace-cap type with light blue to pink sterile flowers and darker fertile ones.
‘Buttons ’n Bows’. Grows 3–4 ft. high and wide, bearing deep pink flowers with white-edged petals.
‘Domotoi’. Well-known old garden selection, featuring clusters of double pink or blue sterile flowers.
‘Endless Summer’. Produces flowers on new growth and blooms all summer. Blossoms are blue or pink, depending on soil pH.
‘Glowing Embers’. Dark pink to red sterile flowers in big, round clusters.
‘Lanarth White’. Reaches 3–4 ft. high and wide. Lace-cap type with white sterile flowers and pink or blue fertile blooms.
‘Lemon Wave’. Rich green leaves edged in yellow; lace-cap flowers in white tinged with pink.
‘Mariesii’. Pink or mauve lace-cap blooms.
‘Merritt’s Supreme’. Rosy red lace-cap flowers. Very showy.
‘Nikko Blue’. Large, round blue blossom clusters. Old standby.
‘Penny Mac’. Vivid blue flowers in 7-in. clusters. Sets buds on both old and new wood—so even if a late frost kills the buds set in autumn, the plant may still bloom on growth formed the next spring.
‘Pia’ (‘Pink Elf’). Only 1 1/2 ft. high and 2 ft. wide, with deep pink sterile flowers.
‘Pink ’n Pretty’. Pink sterile flowers in large clusters.
‘Red ’n Pretty’. Red sterile flowers in big clusters.
‘Variegata’. Unmistakable old lace-cap form with dark green leaves strongly marked in cream and light green.
H. paniculata. Deciduous shrub or small tree. Zones US, MS, LS, CS; 8–1. Native to Japan and China. Best known for its selections. Among the most widely grown is ‘Grandiflora’, peegee hydrangea, an upright, coarse-textured plant that can be trained as a 25-ft. tree but performs best as a shrub to 10–15 ft. high, 8 ft. wide. Pointed oval leaves are 5 in. long, turning bronzy in fall. Large (10- to 15-in.-long), upright clusters of mainly fertile flowers are white, slowly fading to pinky bronze.
Other selections include ‘Kyushu’, with white blooms, and ‘Limelight’, bearing bright lime green flowers. In ‘Pink Diamond’, pink buds open to cream-colored flowers that gradually darken to rosy red; all three colors appear together. ‘Tardiva’ is similar to ‘Grandiflora’ but blooms later, in early and midautumn. Prune all types in late winter.
H. petiolaris. See H. anomala petiolaris
H. ‘Preziosa’. See H. serrata ‘Preziosa’
H. quercifolia. OAKLEAF HYDRANGEA. Deciduous shrub. Zones US, MS, LS, CS; 9–1. From southeastern U.S. Broad, rounded shrub to 6 ft. tall and 8 ft. wide, with handsome, deeply lobed, 8-in.-long leaves that resemble those of oaks, turn scarlet or crimson in fall. Elongated clusters of white flowers in late spring and early summer change to pinkish purple as they age; fertile flowers are usually concealed by larger sterile flowers. Foliage of ‘Alice’ colors a particularly rich red in autumn. ‘Harmony’ features mostly sterile white flowers that weigh down the branches. ‘Semmes Beauty’ is a large plant, to 8–12 ft. tall and 12 ft. wide, with upright flower clusters to an impressive 20 in. across. ‘Sike’s Dwarf’ is a white-flowered selection to only 2 1/2 ft. high and 4 ft. wide. ‘Snowflake’ bears double flowers; as they age, inner sepals stay white, outer ones turn dusty rose. ‘Snow Queen’ is noted for its profuse, dense, upright flower clusters and rich red fall color. Prune right after bloom. Flower buds and stems may be damaged where temperatures go much below –10°F; in these areas, oakleaf hydrangea is best grown for its handsome foliage.
H. sargentiana. See H. aspera sargentiana
H. seemannii. Evergreen vine. Zones LS, CS; 9–8. From Sierra Madre mountains in Mexico. Vigorous grower to 30 ft.; climbs by clinging aerial roots. Leathery, very shiny, elliptical dark green leaves to 6 in. long. White lace-cap flowers emerge from round, showy buds. Pruning is seldom necessary but may be done after flowers fade.
H. serrata. Deciduous shrub. Zones US, MS. LS, CS; 9–6. From Korea, Japan. Resembles H. macrophylla. The species and most selections grow 4–6 ft. tall and wide. ‘Blue Billow’, however, reaches only 3 ft. tall and wide; its blossoms keep their blue color in most soils. ‘Bluebird’ is a lace-cap type with pale blue sterile blooms and deep blue fertile flowers. The lace caps of ‘Grayswood’ consist of bright blue fertile blossoms surrounded by sterile flowers that gradually turn from white to red. ‘Miyama-yae-murasaki’ (‘Purple Tiers’) sports soft pink lace caps of double inner flowers surrounded by double sterile blooms. Pink-blossomed ‘Pretty Maiden’ features unusual lace caps made up of a large cluster of fertile flowers surrounded by very double sterile blooms. ‘Preziosa’ (H. ‘Preziosa’) has round clusters of white sterile flowers that age to red, blue, or mauve. ‘Woodlander’ has shell pink lace caps. Prune all immediately after bloom.
H. villosa. See H. aspera Villosa Group