How to Grow Endless Summer® Hydrangeas

This hydrangea variety is cold-hardy and blooms on old and new growth

Close up shot of purple-blue Endless Summer Hydrangea (Hydrangea macrophylla bailmer)

Anderson Ross / Getty Images

Endless Summer® hydrangeas are cold-hardy, reblooming hydrangeas with stunning blooms in colors such as pink, blue, purple, red, and white. This mophead hydrangea cultivator is the first hydrangea variety that blooms on the previous year’s branches as well as the new season’s growth, offering gardeners across North America the possibility to enjoy gorgeous flowers from early spring through to late summer.

Botanical Name Hydrangea macrophylla 'Endless Summer' 
Common Name  Endless Summer Hydrangea 
Plant Type  Deciduous shrub 
Mature Size  4 feet tall and 3-5 feet wide 
Sun Exposure  Full sun to part shade 
Soil Type  Rich, well-drained soil 
Soil pH  4.5-7.5 
Bloom Time  Spring, summer 
Flower Color  Pink, purple. blue, red, white
Hardiness Zones  4-9, USA
Native Area United States
Toxicity Toxic to pets
Varieties of Endless Summer Hydrangea shrubs in pink,blue, white, and purple.
Paul Fuller / Getty Images

Endless Summer® Hydrangea Care

Endless Summer® hydrangeas are deciduous shrubs with a rounded growth habit that grow to be four feet tall with a spread between three to five feet. They are perfect shrubs for foundation plantings, hedges, containers, border gardens, and more. To better protect these flowering shrubs throughout the growing season, add a layer of organic mulch over the soil to help retain moisture and add nutrients to the soil. 

Light

Endless Summer® hydrangeas enjoy full sun to partial shade. A location that receives morning sun and dappled afternoon shade is ideal. Locations that receive too much sunlight will usually result in fewer blooms throughout the growing season. 

Soil

Nutrient-rich, well-drained soil is ideal for Endless Summer® hydrangeas. While these flowering shrubs can survive in a wide range of pH’s, they tend to thrive in soil that is slightly acidic.

Keep in mind that the soil pH will determine the colour of the blooms. For example, the Original Endless Summer® hydrangea has blue flowers in acidic soil and pink blooms in alkaline soil. This means you can adjust the soil pH depending on what color you want the blooms to be.

Water

Endless Summer® hydrangeas have medium to high water needs. Throughout the growing season, the soil should be kept evenly moist but not waterlogged. Ensuring the plant has proper drainage is imperative in preventing root rot. If you are growing Endless Summer® hydrangeas in containers they will need significantly more water than when grown in the garden. 

Temperature and Humidity

Endless Summer® hydrangeas can grow in USDA zones 4-9, making them accessible for most North American gardeners.

Unlike other hydrangea varieties, Endless Summer® hydrangeas have excellent winter hardiness and can withstand winter temperatures as low as -30 degrees Fahrenheit (or -34.4 degrees Celsius) at the coldest. This means that flowering is quite reliable regardless of winter temperatures. 

Fertilizer

Fertilizer plays an extremely important role in the growth and appearance of Endless Summer® hydrangeas. For the ongoing health of the shrub, apply a balanced NPK fertilizer in the spring or early summer to promote new growth.

To change the soil pH and control the color of the flowers, fertilizers high in ammonium nitrate, ammonium sulfate, or sulfur-coated urea can be used to decrease soil pH and make the soil more acidic, while fertilizers containing lime can help to increase soil pH and make the soil more alkaline.

Are Endless Summer® Hydrangeas Toxic?

All parts of the Endless Summer® hydrangeas are considered toxic to cats, dogs, and horses, and mildly irritating to humans.

Symptoms of Poisoning

While they are rarely fatal, ingesting Endless Summer® hydrangeas can result in the following symptoms.

  • Stomach upset
  • Vomiting
  • Diarrhea
  • Depression/lethargy
  • Skin irritation
  • Rashes

Endless Summer® Hydrangea Varieties

There are five varieties in the Endless Summer® hydrangea collection. The Original was the first re-blooming hydrangea and it remains the most well-known and widespread variety. 

  • The Original Bigleaf Hydrangea - Hydrangea macrophylla ‘Bailmer’
  • Twist-n-Shout Bigleaf Hydrangea - Hydrangea macrophylla ‘PIIHM-I’
  • Summer Crush Bigleaf Hydrangea - Hydrangea macrophylla ‘Bailmacfive’
  • BloomStruck Bigleaf Hydrangea - Hydrangea macrophylla ‘PIIHM-II’
  • Blushing Bride Bigleaf Hydrangea - Hydrangea macrophylla ‘Blushing Bride’

Pruning

Endless Summer® hydrangeas do not require regular pruning and it shouldn't be done during the growing season. However, since these hydrangeas bloom from both old and new wood they can withstand heavy pruning if needed. For best results, wait until the blooming period has ended, ideally in the late summer or early fall.

How to Grow Endless Summer® Hydrangeas From Seed

Endless Summer® hydrangeas can be successfully grown from seed purchased from a nursery or collected from existing plants. For best results, start the seeds indoors in cell packs or seed starting pots. Gently sow the seeds over the top layer of the soil and keep the soil moist at all times. Don’t worry about mixing the seeds into the soil.

Place the seeds in a warm location that receives bright, indirect light. Once the seedlings have established strong roots they can be transplanted into the garden or outdoor container.

When choosing a location for your hydrangea, keep in mind that mature Endless Summer® hydrangea shrubs can reach four feet tall and spread between three to five feet wide. 

Growing Endless Summer® Hydrangeas In Containers 

Endless Summer® hydrangeas make gorgeous container plants and can be easily overwintered in a sheltered garage or shed, or brought indoors for the freezing winter months. Ensure that the potting container has adequate drainage and adjust the watering schedule accordingly.

Common Pests/Diseases

Endless Summer® hydrangeas are susceptible to a couple of common pests and diseases which include powdery mildew, bud blight, leaf spot, bacterial wilt, aphids, Japanese beetles, spider mites, and slugs. Each of these common ailments can be successfully eliminated with proper treatment.

Ensure that you examine your hydrangeas regularly in an effort to catch any pests or diseases early before they become infestations.