Hydrangea Care & Feeding

A classic garden plant that is easy to grow and long-lived, hydrangeas offer a wide variety of stunning colors, styles, and sizes. Below is some straightforward advice for success with hydrangeas.

Site. How much light will the plant receive? Will your hydrangea do best in shade or sun? With some exceptions, most prefer protection from hot afternoon sun.

Soil. In preparing the soil, dig a hole twice as wide and only as deep as the container your plant came in. All hydrangeas prefer compost rich, well-drained soil.

Planting. In a new planting bed it’s best to amend the entire area (by one third) with compost. If preparing an individual hole, replace the same soil back into the hole and mulch the top with compost being careful not to bury the trunk of the plant.

Fertilizing. A yearly addition of compost may be all that is necessary in the first few years. Mature plants will benefit from an all-purpose organic fertilizer, or one for acid-loving plants, such as Dr. Earth. Apply twice yearly, in early spring and again after flowering.

Pests & diseases. Hydrangeas are remarkably disease and insect-free. Powdery mildew is a fungus that can appear on leaves, but allowing for good air circulation around the plants helps control this.

Flower color. This is affected by the relative availability of aluminum in the soil. Acid soils (pH 5.0-6.9) produce blue flowers; alkaline soils (pH 6.0-7.0) produce pink to reddish flowers. When the soil’s pH is above 7.0 the leaves of the hydrangea can begin to yellow. In general, white flowers are not affected by pH. The soil in the Northwest is mostly acidic, so most hydrangeas will tend to be blue. To raise the pH for pink flowers add potassium nitrate well before the flower heads have formed. To lower the pH for blue flowers apply aluminum sulfate.

Pruning. Hydrangeas will grow and flower even if they are never pruned, but you’ll get a better shaped shrub and bigger flowers with some pruning. You can remove dead, damaged, or diseased wood at any time of year. Further pruning should be done in early to mid spring, when buds begin to swell.

It is important to know what type of hydrangea you have since there are several different pruning methods which depend on whether the plant flowers on old wood (last year’s growth) or new wood (current season’s growth). Some hydrangeas like the 'Endless Summer' series bloom on both old and new wood, so pruning is more straightforward.

Method 1
Prune off last season’s flower heads to the first bud or pair of buds beneath the flower heads. With established plants cut back about 1/3 to 1/4 of the oldest flowered shoots to the base; this will promote new growth from the base.

Method 2
Cut down to approximately 1-2 feet. Some thinning is useful to create sturdier stems that will support this plant’s large flowers. This method may also be used to rejuvenate old shrubs, and should be done annually in early to mid spring.

Method 3
For vigorous climbers that flower on old growth no regular pruning is required. Prune to fit available space or as needed after flowering. Thin for light and air on mature plants.

Hydrangea types & pruning methods

Big Leaf Hydrangea. (Hydrangea macrophylla) These are the most common and familiar. Some cultivars include: ‘Blue Wave’, ‘Angel’ series, ‘Endless Summer’, ‘Glowing Embers’, ‘Lady in Red’, ‘Merrit’s Supreme’, ‘Nikko Blue’, ‘Pia’.
These are divided into two groups, Lacecap and Mophead.

Lacecaps. These have flattened flower heads with small fertile flowers in the center, surrounded by larger sterile flowers.
Mopheads. These have nearly round flower heads of large sterile flowers.

Zones 6-9 Pruning Method 1

Mountain Hydrangea. (H. macrophylla subsp. serrata) is a subspecies of bigleaf hydrangea that has slightly smaller leaves and flowers. Cultivars may have either mophead or lacecap type flower. Delicate in appearance, this hydrangea is particularly well suited for placement at the edge of a wooded area. Some cultivars include: ‘Benigaku’, ‘Bluebird’, ‘Preziosa’.   
Zones 6-9 Pruning Method 1

Smooth Hydrangea. (Hydrangea arborescens) Forms a rounded shrub which produces sturdier stems in full sun. In July and August it produces 4-10" ivory flowers atop largely unbranched stems. Flowers fade to a mellow green toward fall. Very hardy with regard to cold, heat, and drought. When wet, plant will splay and weep. Stronger stems produces larger flowers and a tidier shrub. Some cultivars include: ‘Annabelle’, ‘IncrediBall’.
Zones 4-9 Pruning Method 2

Aspera Lacecap Hydrangea. (Hydrangea aspera) These large shrubs have fuzzy, narrow leaves, and blue to purple flowers, and sometimes pink to light purple flowers in July. Tolerant of higher pH.     Some cultivars include: ‘Macrophylla’, 'Robusta', 'Villosa'.    
Zones 6-9 Pruning Method 1

Panicle Hydrangea. (Hydrangea paniculata) Their habit is vigorous and spreading to upright. They produce 6-8" panicle-type white flowers that fade to dusky pink in late summer. Extremely adaptable to different soils. Thin stems can break in the wind, so thin out when pruning to produce stronger ones. These shrubs prefer full sun and flower on new growth. Can be trained to a single-trunked tree to 12' or more. Some cultivars include:  ‘Grandiflora’ (PeeGee), ‘Limelight’, ‘Pinky Winky’, ‘Ruby’, ‘Tardiva’, ‘Unique’.
Zones 4-8 Pruning Method 2

Oakleaf Hydrangea. (Hydrangea quercifolia) Prefers full sun and warmth in the Northwest. Drought tolerant once established, but supplemental water is necessary during drought periods. Attractive features include: papery brown bark, white panicle flowers aging to rose-pink (mid-summer to fall) and oak-shaped leaves with nice fall color. Some cultivars include: ‘Pee Wee’, ‘Snowflake’, ‘Snow Queen’.
Zones 5-9 Pruning Method 1

Climbing Hydrangea. (Hydrangea anomala ssp. petiolaris) Prefers partial shade and develops attractive cinnamon colored flaking bark after a few years. Branches are covered with reddish hairs and aerial roots that develop along the stems; requires sturdy support as it climbs. Slow growing and slow to flower when young. Adaptable to most well-drained soils. Produces large lacecap type white flowers in early summer. Species include: Hydrangea integrifolia (evergreen) shiny, dark green leaves, and Hydrangea seemannii (evergreen) dark green, leathery leaves   
Zones 5-8 Pruning Method 3

Try these knockout combinations:

• ‘Endless Summer’ Hydrangea AND Golden Japanese Forest Grass (Hakonechloa macra ‘All Gold’)
• ‘Glowing Embers’ Hydrangea AND Concorde Barberry (Berberis thunbergii ‘Concorde’)
• ‘Limelight’ Hydrangea AND Rozanne Geranium (Geranium ‘Rozanne’) AND ‘Frosted Violet’ Heuchera
• ‘Lady in Red’ Hydrangea AND Painted Fern (Athyrium nipponicum ‘Pictum’)
• ‘Pia’ Hydrangea AND ‘Elvis Lives’ Hosta