HYDRANGEA. The Americas, East Asia. Ornamental shrubs of many shapes and sizes. They have large, variously toothed, often shiny leaves, mostly deciduous in winter. The flowers can be small individually but are carried in branched, sometimes massive clusters. An interesting feature in several species is the presence of a ring of larger sterile flowers surrounding a group of smaller, fertile flowers, giving the impression of a lace doily. Most species thrive in sun or light shade near the coast. Some shading may be desirable inland. Ordinary soils, regular watering and fertilizing. The following are hardy to 0^oF or less, except as noted.

anomala ssp. petiolaris. Japan, Korea. This is a far cry from the typical garden hydrangea. It is a profusely branched vine, clinging to walls, trees or any other available support with adhesive aerial roots. It has broad, shiny, bright green leaves, 2-4" long, smoother in texture than those of many hydrangeas. In summer flower clusters up to 10" broad are borne at the shoot tips. These are of the lace cap form, and white in color. The effect is spectacular, particularly on a large plant.

 arborescens  ‘Annabelle’. A rounded, well-branched shrub, usually under 5’ tall (typical for the species is 5-10’). It has broad, apple-green leaves 4-6” long. Unlike most plants of this species, which have few or none of the larger sterile flowers,  ‘Annabelle’ carries large pompoms of them from late spring to fall.

arborescens ssp. radiata. I first met this intriguing plant a few years ago on a visit to Heronswood Nursery in Washington. They have kindly supplied material for propagation. It grows a bit more slowly than the typical form, and possibly not quite as tall. The leaves are broadly heart-shaped and dark green on their upper surface. The undersides, however give a striking contrast of chalky grey. The flower clusters are typical of the species, made up of fertile white flowers.

aspera. This is a robust (some would say excessively so) shrub or small tree, growing 8-12’ high and wide. It is somewhat openly branched, with rather thick stems and striking deep green, densely hairy leaves. The leaves are up to 8" long in this form. It is further distinguished by its “lace cap” flower clusters, up to 1’ broad, with blue to purple fertile flowers and white to lavender outer, sterile flowers. It is quite a spectacle, if you have the space to display it properly.

macrophylla. These are the typical garden hydrangeas. They are of moderate size, growing 4-8’ tall and rounded in form. Most are rather widely branched, with heavy, somewhat awkward stems. However, these are well concealed from spring to fall by broad, shiny, deeply veined leaves usually 6-10" long. Two types of flower clusters are represented in the modern hybrids: the lace cap form, described above for the genus, and one made up mostly or entirely of the larger, flatter sterile flowers, often referred to as the mop head type. The overall clusters of some selections are truly monstrous, bowing over the branches which carry them and giving the plants a bedraggled look. Pruning the plants to force rebranching reduces this problem and yields shapelier plants. An interesting feature is the response of flower color to the pH of the soil. Flowers which are pink in neutral or slightly alkaline soil (more than slight alkalinity makes the plants chlorotic) turn blue or lavender in acid soil, though different selections respond to different degrees. Hardy to below 0^oF.

Some notable lace cap hybrids include the following.

‘Geoffrey Chadbund’ is a rather dwarf plant with deep purplish rose to purple flower clusters. Often there is a bicolored presentation of purple fertile flowers ringed by reddish sterile flowers.

‘Lemon Wave’. One of the more recent introductions, with cream, bright yellow and light green variegation on a deeper green background. The flower clusters are large, pale in color and tinged with lilac.

‘Mariesii’ is a robust old-fashioned selection, growing easily 6’ high, with rather pale pink to blue flowers.

‘Mariesii Variegata’ is nearly identical to the original ‘Mariesii’ except for cream-variegated leaves.

‘Pink Lace’. A more recent selection, similar to ‘Mariesii’ but distinguished by  larger and brighter pink flower clusters.

‘Teller Red’ is a lower, more spreading plant with huge clusters of purplish red flowers. The fertile flowers are ringed by a double row of very large sterile flowers.

There are so many mop head hydrangeas that any particular array of them is necessarily somewhat arbitrary. Here are some of the more interesting.

’Domotoi’ is one of the larger cultivars, unusual for its full clusters of semidouble pink to blue flowers.

‘Glowing Embers’ is a truly dwarf (2-3’), compact, smaller leaved plant with smallish clusters of vivid red flowers.

‘Merritt Supreme’ is a robust plant producing an abundance of broad carmine “mops”.

‘Nigra’. A compact, tidy plant notable for its nearly jet black stems and deep green, purple tinged leaves. The flowers are purplish rose in color.

‘Pia’ is even smaller than ‘Glowing Embers’, with rather narrow leaves, only 2-3” long. The flowers are borne in small clusters and colored deep rose pink.

‘Sister Therese’ is a robust plant with large clusters of white, single flowers. It is best when grown in light shade, since the flowers are easily browned by the sun during summer heat waves.

paniculata. H. paniculata is one of the larger species, potentially even a small tree. It has pleasant but undistinguished 3-6" leaves, coloring well in the fall. However, it makes a spectacular show of white flowers, in pyramidal clusters in summer. Those of the more commonly grown cultivar ‘Grandiflora’, nicknamed PeeGee hydrangea, are often 1’ or more long. The selection we received several years ago as  ‘Webb’s’ is a more compact, tidy shrub with bright green 2-3" leaves. The flower clusters seem a little smaller than those of ‘Grandiflora’.

quercifolia. Oakleaf hydrangea. A shrub of moderate growth, reaching about 6’ by 6’. It has large, deeply lobed, fuzzy leaves which color well in the fall. White sterile and fertile flowers are intermixed in pyramidal clusters up to 10" long. ‘Alice’ is a cultivar of typical size but better branched, with 12" clusters. ‘Sikes Dwarf’ is quite compact, growing only about 4’ tall, with smaller leaves and smaller (6-8") flower clusters.

serrata. This species seems to be the subject of a minor taxonomic war. Some botanists include it as a variety of H. macrophylla, which it closely resembles, while others carve out a separate species. I will go with the Royal Horticultural Society for now. Plants included under this heading are of about the same size as those of H. macrophylla, but have generally smaller leaves with noticeably sawtoothed margins. The flower clusters are up to 4" broad and typically of the lacecap form. ‘Blue Bird’ is an attractive, well-formed shrub carrying many bicolored clusters in summer and fall. The inner fertile flowers are deep lavender-blue in color, while the outer sterile flowers are pale lavender. ‘Beni Gaku’ is a similarly attractive plant. The flower clusters are initially cream overall, the outer ring changing to pink and finally to purplish red. ‘Preziosa’ is a compact hybrid, growing 3-4’ high. It has dark stems and closely packed leaves, strongly tinged with red. The flower clusters are of the “mop head” type. The flowers open pink and darken as they age, nearly to crimson.

villosa (aspera ssp. aspera, aspera ssp. villosa). Its botany is confused, but this remains a most beautiful shrub, described by Graham Thomas as “the queen of the tribe”. It grows about 6’ tall, at least 8’ broad, the branches covered by pale, flaking bark. It has large lance shaped leaves, dark green and textured on the upper surface, white-woolly beneath. The flowers are borne in large lacecaps, each showing a ring of pale sterile flowers around a broad cluster of lavender fertile flowers. The effect is stunning overall.