Of all the Perennial Shade Plants Hydrangea Plants are Tops

Known to many gardeners as old fashioned flowering bushes tucked into the shady part of a cottage garden or as a blue or pink flowering potted gift plant, the roughly 75 species of hydrangea plants deserve another look.

Hydrangeas are perennial shade plants in warmer climates and herbaceous part-sun perennials in colder climates. They are fast growing shrubs, and while most species are white flowering, Hydrangea macrophylla, has bright blue or pink flowers commonly sold as gift plants in foil wrapped containers.

Types of Hydrangea Plants

There are four main types of hydrangeas.

Mentioned above, H. macrophylla is native to Japan and is hardy to USDA Zone 6. Also knows as Bigleaf Hydrangea, these flowering bushes normally grow to six feet, but have been know to get 10 feet high.

Bigleaf Hydrangeas may be one of two flower types: Mophead, large globular clusters that will be pink or blue depending on soil alkalinity, or Lacecaps, a pinwheel type flower with small bud-like fertile flowers surrounded by showy non-fertile petals.

Native to the United States, Hydrangea arborescens are the flowering bushes usually associated with cottage gardens. Also known as Smooth Hydrangea, the most popular variety of this type is ‚”Annabelle”.

Smooth Hydrangeas are hardy in USDA Zones 4-9 and usually grow to a height and spread of approximately five feet. The flower heads tend to be globular and on ‚”Annabelle” can have a diameter of up to 12 inches.

Hydrangea quercifolia is also a US native and is the only variety to have seasonal interest. Known as Oakleaf Hydrangea for the shape of its large leaves that turn orange or red in autumn, its flower heads are large and somewhat pointed. The Oakleaf’s flowers bloom pure white but become a faded rose colour as they age.

Oakleaf Hydrangeas are hardy in USDA zones 5-9 and will grow six to eight feet in height.

The fourth type of Hydrangea plant is Hydrangea paniculata, named for its panicule (cone) shaped flower blossoms. Panicle Hydrangeas are sometimes referred to as ‚”PeeGee” which is the most popular variety of this type.

Panicles are Asian natives and hardy in USDA zones 4-7. The only type of hydrangea that can be trained to grow as a tree, panicle hydrangeas can reach 15 feet in height and will tolerate drier conditions than most hydrangea plants. Blooming in mid-summer, the flowers turn a pale pink with age and can remain on the bush long after the leaves have fallen in autumn.

Hydrangea Bush Cultivation

All hydrangea plants are woodland plants, most comfortable in the rich moist soil of shade gardens. The further north the garden, the more sunlight hydrangeas can tolerate. In the most northern zones for hydrangeas, the ideal light is filtered sunlight such that can be found under open branched deciduous trees.

Panicle Hydrangeas can tolerate more sun and drier conditions than other types of hydrangeas.

When planting a hydrangea bush, prepare the soil by digging a wide and deep planting hole and amending with plenty of compost and leaf mold to hold moisture and still allow for good drainage.

Bigleaf Hydrangeas (H. macrophylla) flowers will be blue or pink depending on soil acidity. Soil pH can be altered by adding aluminum sulfate to acidify the soil and make the flowers bluer or by adding lime to the raise the pH and make flowers more pink.

Carefully Prune Hydrangea Plants

In areas where winter is not severe, hydrangea plants will grow new branches on old wood. In colder areas where the hardier hydrangeas grow, the plant may die back to the ground and grow back in spring.

White hydrangea flowers will fade to a dark ivory colour and dry on the branch. They may be left for winter interest without harm to the plant. Remove the dead flowers and branches early in the spring.

H. macrophylla flower on the previous year’s growth and are therefore unable to withstand extremely cold winters. Bigleaf Hydrangeas set their buds in late summer or early fall. Pruning after the flower buds have set will prevent the bush from flowering the following year. To keep Bigleaf Hydrangeas in good shape, prune soon after the flowers have faded. Prune out dead or damaged branches, leaving the old wood for new growth.

The three other types of hydrangeas bloom on current season’s growth. Cut away winter killed branches very early in the spring before new growth has begun or prune the bushes for shape after the flowers have faded.

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Hydrangeas! Hydrangeas!