Bluebird Mountain Hydrangea
Delicate Blue Flowers
Don’t let looks deceive you - this tough, dependable hydrangea is a reliable bloomer.
The mountain hydrangea is a compact, upright deciduous shrub belonging to the Hydrangeaceae family. The ‘Bluebird’ cultivar (Hydrangea serrata ‘Bluebird) is a vigorous grower with lacy flat-topped flowers ranging in color from periwinkle blue to purple-pink, depending on the soil pH. Bluebird mountain hydrangeas are hardy in gardening zones 5-9 and reach a mature size of 4 - 6 feet high and wide.
As temperature fluctuations in late winter and early spring have become more problematic for bigleaf hydrangeas (Hydrangea macrophylla), gardeners are reconsidering mountain hydrangeas as a tougher, more dependable addition to the garden. Mountain hydrangeas stay dormant longer and bloom later than bigleaf hydrangeas. This creates more reliable flower production in regions like the Mid-Atlantic, where early spring frosts kill the buds of bigleaf hydrangeas, leaving gardeners with reduced or even non-existent flowering for the season.
Mountain hydrangeas are native to the mountainous regions of Korea and Japan, and the Bluebird cultivar grows best when planted in cool, moist, rich soil that mimicks this environment. They will grow in full sun, but do best in partial shade, especially when kept out of harsh afternoon sun. Bluebird mountain hydrangeas do not wilt as easily as their bigleaf cousins - they have smaller leaves, which give them an advantage in dealing with heat and humidity. In summer, Bluebird mountain hydrangeas are covered with clusters of blue to purplish pink flowers with a flat top and lacy appearance. The flowers are comprised of large, sterile, showy florets surrounding small, delicate, fertile flowers with colored stamens. The blooms last until late summer, and fall color is a brilliant red. Bluebird mountain hydrangea is one of the best hydrangeas to plant for stunning fall color.
Bluebird mountain hydrangeas are relatively unbothered by diseases and insect pests. Like all hydrangeas, they can develop fungal problems when overwatered. Soil chemistry will turn Bluebird mountain hydrangea flowers either blue or purple-pink. If you would like to change the bloom color of your mountain hydrangea to deep blue, add acidic garden sulfur. To turn the blooms a pinker shade, make the soil more alkaline by adding garden lime. And be patient, it can take months changes to become evident!
How to Plant and Grow Mountain Hydrangea
Planting: The best time of year to plant a mountain hydrangea is in the spring or fall, giving the roots time to establish before the onset of extreme hot or cold weather. Water deeply immediately after planting.
Location: Choose a location with well-drained soil that is rich in organic matter. Mountain hydrangeas prefer soil that retains moisture but does not become waterlogged. Select a spot with partial shade - while mountain hydrangea can tolerate full sun, it prefers partial shade and protection from the intense afternoon sun.
Soil: Amend the soil with organic matter, such as compost, shredded leaves, or Leaf-gro®, to improve drainage and soil fertility. If you would like your mountain hydrangea to bloom specifically pink or blue, consider getting a soil test and adding either sulfur or lime to the soil. Add sulfur for blue flowers and lime for pink blooms.
Mulch: Apply a layer of organic mulch around the base of the plant to retain soil moisture, regulate temperature, and suppress weeds.
Watering: Keep the soil consistently moist but not waterlogged, especially during periods of drought. Deep watering is preferable to encourage the development of a strong root system (Are you in a drought? Check the U.S. Drought Monitor).
Fertilization: Hydrangeas typically do not need fertilization when they are given the rich, fertile soil they prefer. Each spring, spread a layer of compost, shredded leaves or Leaf-gro® around the base of your hydrangea, being careful to keep it away from the base of the shrub.
Pruning: Mountain hydrangeas bloom on old wood and look their best with minimal pruning. If needed, prune to shape in late summer when flowering has finished. Avoid pruning in fall, winter, or early spring as you risk removing flower buds and diminished flowering. Do not cut back mountain hydrangeas in the fall.
Pest and Diseases: Mountain hydrangeas are relatively pest resistant; aphids are an occasional problem. Mountain hydrangeas are prone to powdery mildew and leaf spot - ensure good air circulation to minimize the risk of diseases, and practice good watering habits (see “How to Water your Plants” to brush up on your watering skills).
Do Bluebird Mountain Hydrangeas Like Sun or Shade?
Bluebird mountain hydrangeas thrive in partial shade (2-4 hours of direct sunlight per day). While they can tolerate some sunlight, mountain hydrangeas prefer dappled or filtered light, with protection from the intense hot afternoon sun. In hot climates, providing them with morning sun and afternoon shade can help prevent their flowers and leaves from wilting and scorching. In cooler regions, they may tolerate more sun, but protection from harsh afternoon sunlight is still recommended.
Bluebird mountain hydrangea (Hydrangea serrata ‘Bluebird’)
Adding garden sulfur turns mountain hydrangea blooms blue; adding garden lime turns blooms pink.
Landscape Design Ideas for Mountain Hydrangea
Mixed Border Planting: Create a mixed border planting with mountain hydrangeas along with other complementary shade-loving plants such as astilbe, ferns, and Japanese forest grass. This will add layers of texture and color to your garden.
Woodland Garden: Incorporate mountain hydrangeas into a woodland garden setting. Under the dappled shade of trees, these hydrangeas will thrive and provide a provide flowers all summer long.
Container Gardening: Use larger containers, pots, or planters to showcase mountain hydrangeas in a shadier corner of a a patio or deck.
Accent Planting: Use mountain hydrangeas as accent plants to highlight certain areas of the garden. Planting near a water feature or along a pathway can draw attention to these beautiful shrubs.
Foundation Planting: Incorporate mountain hydrangeas into your foundation planting to add visual interest and soften the lines of your home. They work well when paired with partial-shade loving evergreen shrubs like Himalayan sweetbox (Sarcococca hookeriana var. humilis) or spreading Japanese plum yew.
Mass Planting: Create a striking display by mass planting mountain hydrangeas in larger garden areas, like a shady slope or property line. Soften a wooden fence with a row of mountain hydrangeas running along the length, or fill up a shaded side yard with a mass planting of mountain hydrangeas next to a stepping stone pathway.
The lacy, flat-topped flowers of bluebird mountain hydrangea (Hydrangea serrata ‘Bluebird’).