Hydrangeas are easy, classic flowering shrubs for our area with a long history. We love them for their big summer show of bountiful blossoms. There are several different types available and each has its own site requirements and pruning needs.
Annabelle Hydrangeas
(Hydrangea arborescens)
Flowers: Blooms in late June, early July. Large rounded mophead flowers that start green, turn white, go back to green, then dry out and become papery. Usually we leave the dried flowers on the plant for winter interest and deadhead them in the spring. Best flowering occurs in part shade. Blooms on new wood.
Habit: Upright, loose, and billowy. Stems will slowly colonize.
Fall Color: None appreciable.
Bark: Smooth reddish-brown on old stems, green on new.
Size: 4 to 5 feet high and wide, although they will slowly spread. If cut back each spring, they will grow about 3 feet in a season. Once they reach about 5 feet, they don’t get taller.
Sun: Part shade to full shade.
Soil: Average to moist.
Pruning: Deadhead in the spring. If you want the plants to be shorter, cut them back to a couple of inches of soil level in March. However, you will create younger, weaker stems, so flowers may flop more.
Cultivars: Incrediball – bigger stems, bigger flowers. Incrediball Blush – pale pink flowers. Invincibelle Spirit – pale pink flowers.
Big-Leaf Hydrangeas
(Hydrangea macrophylla)
Flowers: Blooms beginning in June, then through the summer into October. Large mophead or lacecap flowers that change color depending on soil acidity. They will be pink in Illinois soils unless you add an acid fertilizer, then you can turn them lavender or blue. Add a cupful of fertilizer around the roots in early spring and again in September. Deadhead faded blooms as they tend to shatter once they go papery. Deadheading also promotes new bud formation, although it’s not essential to keep it flowering all summer. Best flowering occurs on old wood, although there are many cultivars that flower on both old and new wood.
Habit: Rounded.
Fall color: Reddish-purple.
Bark: Dark reddish-brown.
Size: About 3 feet high and wide, growing 2 to 3 feet in a season. These will not get much taller than about 3 feet.
Sun: Part shade to full shade.
Soil: Average to moist.
Pruning: Leave stems up all winter for less winter damage and cut the dead bits off when they start budding out in the spring. Cold damage starts at the tips of the stem and works its way down, so the more stem you have, the better chance at living tissue when we come out of winter. This type of hydrangea will have dormant flower buds held on the stems all through winter, so protection from winter wind (our winter winds generally come from the northwest) is commonly recommended. For those cultivars that only bloom on old wood, you may get lots of great foliage, but no flowers because the buds were all winter-killed. For these, consider treating them as you would a hybrid tea rose. When the ground is truly frozen in December, do a mound of mulch around the crown up about a foot. Pull the mulch away in March when we start warming up.
Cultivars: Lots! When looking at this type of hydrangea, you need to think about how it blooms. The Let’s Dance, Bloomstruck, Endless Summer, and Endless Revolution cultivars all bloom on old and new wood. The Cityline and Lemon Daddy cultivars bloom on old wood.
Panicle Hydrangeas
(Hydrangea paniculata)
Flowers: Blooms in late June, early July. Large conical flowers bloom white, then as petals age, they turn shades of pink to magenta. Flowers then dry, go papery, and hold for winter interest. Usually we leave the dried flowers on the plant for winter interest and deadhead them in the spring. Best flowering occurs in full sun. Blooms on new wood.
Habit: Upright, loose vase shape. Also trained as a tree.
Fall color: Yellow, although Quick Fire turns orange.
Bark: Pale grey.
Size: 6 to 8 feet high and 5 to 6 feet wide, but there are many shorter cultivars. The large varieties grow about a foot a year. The dwarf cultivars will do between 3 and 6 inches.
Sun: Full sun to part shade.
Soil: Average to well-drained soils.
Pruning: Deadhead dry flowers in spring. To control size, you can prune them in late winter. However, with the explosion of different cultivars, you can typically find one that will get the size you want.
Cultivars: Lots! Vanilla Strawberry, Pinky Winky, Limelight, and Quick Fire all get large. Little-Lime, Firelight, Magical Flame, Strawberry Sundae are medium sized. Bobo is the shortest of the bunch at 3 to 4 feet.
Oakleaf Hydrangea
(Hydrangea quercifolia)
Flowers: Blooms in late June, early July. Huge conical flowers that bloom white and then as petals age, turn rose to magenta before dying out and becoming papery. Usually we leave the dried flowers on the plant for winter interest and deadhead them in the spring. Blooms on old wood.
Habit: Loosely rounded.
Fall Color: Reddish-purple. Outstanding!
Bark: Reddish-brown and peeling.
Size: 6 to 8 feet, although there are shorter cultivars. Grows about 6 inches a year.
Sun: Part shade.
Soil: Average to well-drained soils.
Pruning: Only if you have to. It blooms on old wood and grows slowly, we don’t usually prune oakleaf hydrangeas unless absolutely necessary. Protect this one from rabbits over the winter, as they like to nibble the stems when the shrubs are small.
Cultivars: Many! Ruby Slippers stays about 4 to 5 feet and the petals age to a rich magenta. Alice is a classic large variety. Gatsby Star has doubled flowers. There are more available.
Mountain Hydrangea
(Hydrangea serrata)
Flowers: Large lacecap flowers beginning in June and blooming into October. These also change color from pink to blue, depending on soil acidity. Deadhead faded blooms as they tend to shatter once they go papery. Deadheading also promotes new bud formation, although it’s not essential to keep it flowering all summer. Blooms on old and new wood.
Habit: Rounded.
Fall color: Burgundy.
Bark: Dark reddish-brown.
Size: 2 to 3 feet.
Sun: Part shade to full shade.
Soil: Average to well-drained soils.
Pruning: Leave stems up all winter for less winter damage and cut the dead bits off when they start budding out in the spring. This type of hydrangea will have dormant flower buds held on the stems all through winter, so protection from winter wind (our winter winds generally come from the northwest) is commonly recommended. This type is the newest hydrangea on the market and is supposed to be hardier than H. macrophylla.
Cultivars: Tuff Stuff – blossoms can change color and is 2 to 3 feet. Tiny Tuff Stuff – blossoms can change color and is just 2 feet. Tuff Stuff Red – blossoms stay a bright cherry pink and is 2 to 3 feet.