Hydrangea macrophylla 'Bailmer'

endless summer hydrangea

Attracts Pollinators Attracts Butterflies Container Friendly

SunPart Shade – Full Sun

HardinessZones 4–9

Overview

Hydrangea macrophylla 'Bailmer' is a deciduous shrub reaching 3-5 feet (90-150 cm) tall and 3-5 feet (90-150 cm) wide with a rounded mounded habit. Leaves are ovate, 4-6 inches (10-15 cm) long, with serrated margins and a glossy medium-green surface. Flowers form large mophead clusters 6-8 inches (15-20 cm) across, composed of sterile sepals; color shifts with soil pH, producing blue tones at pH 5.0-5.5 with available aluminum and pink tones at pH 6.0-6.5 with low aluminum. Unlike most H. macrophylla, 'Bailmer' produces flowers on both old wood (June bloom) and new wood (July through October), continuing to flower even after stems are killed by late frost. Annual growth is 12-18 inches (30-45 cm); plants reach mature size in 3-4 years. Stem dieback occurs at -10°F (-23°C); plants regrow from the crown but lose the early-season bloom flush in those years. Flower color shifts and fades within 4-6 weeks of opening, transitioning through dusty pink, mauve, and tan as sepals age.

Native Range

Hydrangea macrophylla is native to coastal Honshu and Shikoku, Japan, where it grows in moist woodland edges and coastal slopes from sea level to 5,000 feet (1,500 m) elevation. The species was introduced to European gardens in the late 18th century and has been bred extensively for cut-flower and landscape use. 'Bailmer' was selected in Minnesota in the 1980s and patented in 2003 (US PP15,298) by Bailey Nurseries.

Suggested Uses

Planted in mixed borders, foundation plantings, and woodland edges at 4-5 feet (1.2-1.5 m) spacing. Grows in 7-10 gallon (26-38 L) containers with weekly watering and annual fertilization. The repeat-bloom habit allows hedge use in zones 4-5 where H. macrophylla cultivars without rebloom often fail to flower after winter dieback.

How to Identify

Identified by mophead inflorescences 6-8 inches (15-20 cm) across composed entirely of sterile florets. Distinguished from other H. macrophylla mopheads by stem buds that produce flowers on new wood as well as old wood, continuing to bloom from July onward. Stems are red-tinted at the nodes; leaves are slightly thicker and more leathery than typical species forms.

Appearance

Size & Dimensions

Height3' - 5'

Width/Spread3' - 5'

Reaches mature size in approximately 4 years

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~16 weeks

Summer Fall

Initial bloom from old-wood buds opens in early to mid-June in zones 5-7 and late May in zones 8-9. New-wood reblooming begins in mid-July and continues through first frost in October-November, with the heaviest flush in August. Individual mopheads remain in color for 4-6 weeks before fading. In zones 4 and colder, old-wood bloom is often lost to winter dieback; new-wood bloom from July onward becomes the main flowering window.

Detailed Descriptions

Flower Description

Blue at low pH; pink at higher pH

Foliage Description

Medium green

Growing Conditions

Sun Requirements

SunPartial Shade SunFull Sun

Requires 4-6 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.0 - 6.5(Acidic)

357912

Soil Types

loam clay

Drainagemoist

Water & Climate

Water Needs

High

Frost Tolerance

hardy

Time to Maturity

3-4 years

Care & Maintenance

Care Guide

Plants establish in 1-2 growing seasons with consistent moisture; water deeply 2-3 times per week during the first summer if rainfall falls below 1 inch (2.5 cm) per week. Mature plants wilt at midday during heat above 90°F (32°C) but recover overnight if soil moisture is adequate. Blue flowers develop at soil pH 5.0-5.5 with available aluminum (aluminum sulfate at 1 lb per 10 sq ft / 0.5 kg per 1 sq m in spring); pH above 6.0 produces pink flowers. Leaf scorch develops in afternoon sun in zones 7 and warmer. Powdery mildew and Cercospora leaf spot occur in still humid air; both are cosmetic. Flower buds are damaged by temperatures below -10°F (-23°C), eliminating old-wood bloom for that season.

Pruning

Remove dead stems and cut spent flowerheads to the first pair of strong buds in late winter (February-March). Heavy pruning of live wood reduces the old-wood bloom, which develops on the previous year growth. Stems killed to the ground by winter freeze regrow from the crown and bloom on new wood from July onward. Removal of faded flowers throughout summer redirects energy into new-wood reblooming.

Pruning Schedule

winter