How to Grow and Care for Endless Summer Hydrangeas

This brand of hydrangea is cold hardy and blooms on old and new stem growth

Purple and white Endless Summer hydrangea flowers with large leaves closeup

The Spruce / Gyscha Rendy

Endless Summer® is a brand of several cold-hardy reblooming hydrangeas. Their stunning blooms are available in several colors: pink, blue, purple, red, and white. These mophead hydrangea (Hydrangea macrophylla) cultivars bloom on the previous year’s stems as well as the new season’s stems, which is not the typical bloom habit of mophead hydrangeas.

The Endless Summer bloom habit provides flowers from spring through to late summer. With its rounded growth habit and dense, broadly ovate green leaves, it is the perfect flowering shrub for foundation plantings, containers, perennial flower borders, and anywhere in your landscape where you want colorful blooms.

Hydrangeas are toxic to humans and dogs, cats, and horses.

Common Name  Endless Summer hydrangea 
Botanical Name Hydrangea macrophylla Endless Summer
Family Hydrangeaceae
Plant Type  Shrub 
Mature Size  3-5 ft. tall, 3-5 ft. wide 
Sun Exposure  Partial sun
Soil Type  Loamy, moist, well-drained 
Soil pH  Acidic, neutral, alkaline
Bloom Time  Spring, summer 
Flower Color  Pink, purple. blue, red, white
Hardiness Zones  4-9 (USDA)
Native Area Cultivar, no native range
Toxicity Toxic to people, toxic to dogs, cats, and horses

Endless Summer Hydrangea Care

Endless Summer hydrangea is a collection of several Hydrangea macrophylla cultivars that bloom all summer long. Like all hydrangeas, they do best in soil with plenty of organic matter so amending the soil before planting is important for plant health and blooming. After planting, spread a layer of organic mulch around the plant to help retain moisture and add nutrients to the soil. When spreading mulch, be sure that it doesn't touch the base of the plant.

Deep purple and light purple Endless Summer hydrangea flower clusters

The Spruce / Gyscha Rendy

Light green, purple, and white Endless Summer hydrangea flower clusters on stems

The Spruce / Gyscha Rendy

Purple and white Endless Summer hydrangea flower cluster surrounded by leaves

The Spruce / Gyscha Rendy

Light

Endless Summer hydrangeas grow best in partial sun. A location that receives morning sun and dappled afternoon shade is ideal. If these hydrangeas are planted in full sun, conditions might be too hot and intense for the plants to produce blooms. Planting in too much shade can result in weak stems and fewer blooms.

Soil

Nutrient-rich, well-drained soil is ideal for Endless Summer hydrangeas. While these flowering shrubs tolerate a wide pH range (4.5 to 7.5), they tend to thrive in soil that is slightly acidic.

Except for the Endless Summer 'Blushing Bride' variety, which has white blooms, the soil pH level and aluminum content determines bloom color. A soil pH below 6.0 produces blue blooms, and a soil pH above 6.0 produces pink blooms.

Be aware that if you add a sulfur-based soil acidifier to lower soil pH, adding too much aluminum sulfate can increase the salinity of the soil, which might prevent the hydrangea from blooming. Contact your local extension office to conduct a complete soil test to check that the salinity (EC) is between 1 and 3.

Be aware that results from adjusting soil pH are not instantaneous, it might take a season or two for the amendments to take effect.

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 to prevent root rot.

Endless Summer hydrangeas make gorgeous container plants. Just keep in mind that they will need significantly more water during the growing season than garden-grown plants.

Temperature and Humidity

Endless Summer hydrangeas are hardy in USDA hardiness zones 4 to 9, making them available 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

The general recommendation for feeding your hydrangea is to apply one cup of a granular fertilizer in spring or early summer to promote plant health. Any more than that is overkill. Over-fertilizing can burn the root system and actually inhibit bloom production.

Use a granular, slow-release fertilizer with an NPK ratio of 10-30-10, which contains a higher percentage of phosphorus. Phosphorus is the middle number in the NPK ratio. If you cannot find that specific nutrient combination, look for a fertilizer that has a higher ratio of phosphorus (P) than the other two nutrients. Phosphorus promotes blooming.

Do not use a fertilizer with a higher percentage of nitrogen (N) because that can result in lush foliage but few blooms.

Types of Endless Summer Hydrangeas

The Endless Summer collection contains several cultivars. The 'Original Bigleaf Hydrangea' was the first re-blooming hydrangea discovered and it remains the most well-known and widespread . 

  • Hydrangea macrophylla 'Original Bigleaf Hydrangea' : This variety grows three to five feet tall and wide with blue, purple, or pink blooms.
  • Hydrangea macrophylla 'Twist-n-Shout®': This variety has a lacecap flower form and grows three to five feet tall and up to four feet wide with deep pink or periwinkle blue blooms.
  • Hydrangea macrophylla ''Summer Crush®': This compact variety can tolerate more sun than the other varieties and grows 18 to 36 inches tall and wide with raspberry red or neon purple blooms.
  • Hydrangea macrophylla 'BloomStruck®' : This variety grows three to five feet tall and up to six feet wide with vivid rose-pink, blue, or purple blooms.
  • Hydrangea macrophylla ‘Blushing Bride' This is the only variety where soil pH cannot change the initial bloom color. This variety grows three to four feet tall and wide with pure white blooms, which mature to blush pink or Carolina blue.

Pruning

Endless Summer hydrangeas require minimal pruning. Never prune them in the fall. If at all, spring is the time to prune without the risk of removing flower buds. Wait until green leafy growth appears on the stems. Make sure to remove only dried out brown buds located higher up on the stems. Don't remove the green buds on the lower part of the stems, as these will be the first buds to bloom. The new stem growth occurs at the base of the plant and this where blooms will emerge later in the summer.

Propagating Endless Summer Hydrangeas

The Endless Summer collection is a registered trademark and propagating it by cuttings or seeds is prohibited by a plant patent.

Overwintering

Endless Summer hydrangeas are hardy to USDA cold hardiness zone 4 and need no winter protection when grown in the garden. The exception is when the plants are container grown. To prepare your container-grown Endless Summer hydrangea for overwintering, stop fertilizing them around the end of July or early August. Don't prune them in the fall.

In cold climates, overwinter the container in a sheltered location such as an unheated garage, greenhouse, shed, or basement. For containers that are too large to move, cover the base with a thick layer of mulch and wrap the container in burlap or another thick textile to insulate it from the cold.

If you live in a warmer climate, leave the potted hydrangea outdoors but move it to a location where it is protected from chilling winter winds.

Water the plants about once every month; they don't need much water during the winter but don't let them dry out. If you leave them outdoors, water them if rainfall is sparse.

Common Pests and Plant Diseases

Endless Summer hydrangeas are susceptible to a few 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. Prevent powdery mildrew by providing plenty of air circulation around plants.

Remove aphids or spider mites with a blast of water from the hose or a shot of insecticidal soap. Hand pick beetles from the plants and drop them into soapy water. Lure slugs away from plants with baits or spread a ring of diatomaceous earth around the base of the plant (this only works in dry conditions).

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

FAQ
  • How do you keep Endless Summer hydrangeas blooming?

    The best location to ensure continuous bloom is one where the plant receives morning sun and afternoon dappled shade. In too much sun, they might stop blooming.

  • Do you deadhead Endless Summer hydrangeas?

    Endless Summer hydrangeas benefit from deadheading to make room for the next bloom. Remove the spent flowers just below the flower head and above the next set of leaves.

  • How long does it take to change the flower color of an Endless Summer hydrangea?

    It depends on the pH level of your soil. If your soil is alkaline and you want blue flowers, which require a soil below 6.0, it might take one year or more to gradually acidify the soil. If your soil is already in the neutral pH spectrum, around 7.0, soil acidification happens faster and you might see blue flowers in the same season.

Article Sources
The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. University of California Agriculture, and Natural Resources. “Toxic Plants (by Common Name).” Ucanr.Edu, https://ucanr.edu/sites/poisonous_safe_plants/Toxic_Plants_by_common_Name_659/

  2. “Hydrangea.” ASPCA, https://www.aspca.org/pet-care/animal-poison-control/toxic-and-non-toxic-plants/hydrangea

  3. “Hydrangea Planting and Care.” Endless Summer, 6 Mar. 2020, https://endlesssummerblooms.com/resource/hydrangea-planting-and-care/

  4. “FAQ.” Endless Summer, 25 Feb. 2020, https://endlesssummerblooms.com/resource/faq/

  5. “How Do I Protect My ENDLESS SUMMER Hydrangea over the Winter?” Extension, https://extension.unh.edu/blog/2017/12/how-do-i-protect-my-endless-summer-hydrangea-over-winter