How to Grow and Care for Bloomstruck Hydrangea

New and Improved Endless Summer Hydrangea

Bloomstruck hydrangea plant with bright pink flower clusters on end of stem and veined leaves

The Spruce / Adrienne Legault

Bloomstruck hydrangea belongs to the "bigleaf" category of hydrangea bushes. Unique to this type of hydrangea, the soil's pH level color determines the flower's color. Bloomstruck hydrangea is a popular cultivar in the Endless Summer series because it reblooms. Bloomstruck hydrangea is an ornamental shrub that produces large (3.5 to 5 inches across), mophead-style flower heads with attractive reddish-purple branches and dark-green leaves. This plant can be planted in spring or fall, growing very fast. Hydrangeas are toxic to humans, cats, dogs, and horses.

Common Names Bloomstruck hydrangea
Botanical Name Hydrangea macrophylla 'P11HM-11'
Family Hydrangeaceae
Plant Type Deciduous shrub
Mature Size 3 to 4 feet high and 4 to 5 feet wide
Sun Exposure Partial
Soil Type Well-draining, moist
Soil pH Below 5.5 for blue flowers, 5.5 to 6.5 for purple flowers, above 6.5 for reddish flowers
Bloom Time July and August
Flower Color Blue, purple, red
Hardiness Zones  4 to 9
Native Area Asia
Toxicity Toxic to humans, dogs, cats, horses

Bloomstruck Hydrangea Care

This plant requires little maintenance if you are not fussy about flower color. Otherwise, you will need to think about amending the soil to change the pH, raising or lowering the soil's acidity or alkalinity. Pruning is not necessary other than removing dead, diseased, or winter-damaged branches, or removing branches that are rubbing against each other, or jutting out in a way that spoils the shrub's overall shape.

Bloomstruck hydrangeas work well in summertime hedges since they furnish the yard with excellent color when in bloom. You can also use Bloomstruck hydrangeas in shrub borders along property lines, but since they are deciduous, they do not give you much privacy outside of the summer and fall seasons.

Bloomstruck hydrangea shrub with tall stems and pink flower clusters on branch ends

The Spruce / Adrienne Legault

Bloomstruck hydrangea plant with pink flower clusters in between bright green and veined leaves

The Spruce / Adrienne Legault

Bloomstruck hydrangea flower clusters with bright pink petals closeup

The Spruce / Adrienne Legault

Bloomstruck hydrangea plant with light pink and yellow flower clusters on dark red stems

The Spruce / Adrienne Legault


Bloomstruck hydrangea grows best in part shade. In the North, hydrangeas can tolerate full sun if their soil remains evenly moist; if not, grow it in filtered sun or partial shade.


Enrich the ground (and improve its drainage simultaneously) by mixing in generous amounts of decomposed organic matter. Plants grown in containers need loose soil that provides good drainage and plenty of aeration. You can use a well-draining potting mix or an all-purpose potting soil mixed halfway with perlite or peat moss.


The shrub has average water needs if grown in partial shade, especially in the North. Average water means about an inch per week or 1/2 gallon a week. It is recommended to spread that watering out every third day or so. Mulching will help the soil retain the moisture it needs.

Temperature and Humidity

USDA hardiness zones indicate where your plant can withstand the region's temperatures. Endless Summer hydrangeas grow in zones 4 through 9 and can grow throughout most of the country. They are cold-hardy enough to handle frost and tolerate heat if the plant has shelter or protection from a scorching sun. Hydrangeas prefer average to high humidity. Most plants outdoors will survive fine with the ambient moisture; however, any hydrangeas raised as houseplants will need misting, a humidifier, or will need to be kept on a tray of pebbles to raise their humidity level.


Hydrangeas like fertile soil; enrich its growing medium annually with compost or manure tea. Or, you can give an all-purpose, balanced fertilizer like 10-10-10 NPK once early to mid-spring and then every three months or so (suspend feeding in winter). To increase the size and quantity of hydrangea blooms, consider a fertilizer with more phosphorus. Phosphorus is the middle value, so a fertilizer labeled 10-20-10 will do. If exploring slow-release granular fertilizer, choose one labeled "bloom boost," which may also have a higher level of phosphorus.

Types of Endless Summer Hydrangeas

Depending on your landscaping needs and preferences, you can choose from nine types of hydrangeas, ranging from bigleaf to climbing, vining type. Endless Summer is the brand that engineers Bloomstruck and four other hydrangeas to bloom all season long, year after year. They are valued for their reblooming properties (also called "remontant"). They are shrubs that flower on old wood and new growth:

  • The Original Bigleaf: Grows 3 to 5 feet tall and wide; pink and blue flowers
  • Summer Crush: Plentiful, big red and purple blooms; 18 to 36 inches tall and wide
  • Twist-n-Shout: Reblooming lacecap hydrangea; deep pink or periwinkle blue flowers; 3 to 5 feet tall and wide
  • Blushing Bride: Pure white semi-double florets that make big round balls; white flowers mature to blush pink or Carolina blue; 3 to 6 feet tall and wide


Bloomstruck blooms on both old and new growth, so technically, they do not require pruning at all. It's a personal preference. Some only prune stems that appear dead, dying, or diseased.

You can clean up the dead stems in early spring as the winter chill starts to ease up. You can prune down to the base, reenergizing the plant to grow healthy and bloom again in the summer.

To prune Bloomstruck during the summer, cut one or two of the oldest stems down to the base to encourage fullness and branching. If your plant is in zone 4 or 5, prune very little, and if you feel you need to, do it immediately after blooming.

Propagating Bloomstruck Hydrangea

As a trademarked cultivar, propagating Bloomstruck hydrangeas for sale is prohibited. However, most hydrangeas are easy to propagate from cuttings. The best time to propagate is in the early fall. This plant will not be harmed when you take cuttings and welcomes getting pruned to stimulate new growth. You can root cuttings in soil or water; here's how to do it:

  1. You'll need sterilized pruning snips, well-draining potting soil, an 8- or 10-inch pot (terra-cotta is a suitable type), and rooting hormone (or a clear glass of water).
  2. Using a sterilized set of pruning snips, clip off a healthy 6- to 8-inch stem that does not have flowers on the stem, cut just below a leaf node (where leaves grow out of the stem). Keep the topmost set of leaves on the stem, removing all the rest of the leaves.
  3. Dip the cut-end in rooting hormone.
  4. Plant the cut-end into a pot filled with damp potting soil.
  5. Cover the pot with a clear plastic bag and close it at the bottom of the pot. Do not let the bag touch any of the leaves. You can cut a few slits at the sides of the bag or open the bag an hour each day for air circulation. Maintain moist (but not soggy) soil by misting or watering frequently.
  6. Leave the pot in a warm spot but not in direct sunlight.
  7. The cutting should root within two to four weeks. You'll know it has roots if you see new growth, and when you gently tug the stem, you get resistance. Once it's got roots, it's ready to transplant.
  8. Instead of using rooting hormone and directly planting the cutting, you can root the cut end in a clear glass of filtered water placed in indirect light. Remove the bottom leaves up to the waterline. It may take much longer than rooting it soil—about two months or so. Replenish the water to maintain the same waterline, every few days. Give the water a complete change every 10 to 14 days. Once the roots are 1 to 2 inches, it's ready to pot in well-draining potting soil.

Potting and Repotting Bloomstruck Hydrangea

If potting up transplants, terra-cotta pots work well since these porous pots absorb water, promoting a hospitable growing environment for hydrangeas. To repot hydrangea, choose a pot that is one or two sizes larger than the current pot. Get a pot that has a wide, flat base since hydrangeas can get top-heavy. The flat base works best when placing your hydrangea outside, as they provide support and resist tipping in the wind. Inexpensive pots, like those from the greenhouse, can be used if you intend to sink the pot into the soil for the summer.


Under extreme weather conditions, most bigleaf hydrangeas will not bloom (or will bloom poorly) some years due to plunging temperatures, sudden or wide temperature fluctuations, icy conditions, and late frosts. Although Bloomstruck hydrangeas can survive in USDA zone 4 temperatures, they are only winter hardy when they have protection in zones 4 to 6. In cooler zones, protect your plants with shelter from harsh winds, including a burlap wrap of stems or circle of chicken wire filled with leaves or straw to a depth of 8- to 12-inches in circumference. Or, if they're in containers, bring them indoors during the winter.

Common Pests & Plant Diseases

Hydrangea macrophylla, as a class, is susceptible to plant diseases such as bacterial wilt, blight, leaf spot, and powdery mildew (although Bloomstruck hydrangea tends to have better resistance to powdery mildew than the overall species does). You can reduce instances of powdery mildew through liberal spacing (which promotes better air circulation) and by avoiding overhead watering (place the nozzle of your garden hose down at soil level, instead, when watering).

For insect pests, aphids are the biggest problem. Inspect the undersides of the leaves faithfully in case aphids find their way to your plants. Spray with Neem oil as soon as you detect the presence of aphids.

How to Get Bloomstruck Hydrangea to Bloom

Hydrangea flower heads make for good cut flowers, although they aren't fragrant. Endless Summer Bloomstruck flowers should rebloom all summer long. You can safely cut some branches without harming your plant. But, be extra careful when pruning. Hydrangeas begin forming the buds for next year's blooms shortly after blooming. Sometimes you can mistakenly prune off next year's blooms. Over-pruning is a common reason why Bloomstruck hydrangeas don't bloom.

If your hydrangeas are not blooming, it could be incorrect pruning, damage to buds during the winter, or at some point, you may have overfertilized the plant. You can deadhead after flowers fade to encourage new buds.

Common Problems With Bloomstruck Hydrangea

Hydrangeas look like a fussy plant; however, appearances are deceiving. This plant is relatively easy to care for as long as you plant it in the right location, controlling sun exposure, and maintaining moist, well-draining soil for your plant.

Drooping Leaves

During sweltering temperatures, your Bloomstruck plant's leaves droop when it needs more water. It also requires more water during the blooming period. Just add water to revive drooping leaves.

Yellowing Leaves

Yellowing leaves on a hydrangea can mean many things: overwatering, underwatering, or too much fertilizer. Water management will be your best line of treatment and defense. Check the soil. If it's too soggy, let the plant dry out by not watering for a few days.

Plants kept in containers dry out quicker than plants in the ground—the water drains away, and many roots compete for the water. If you have a potted plant, pull it out of the container and check the root system. If the plant appears rootbound with roots growing out of drainage holes and overtaking the soil in the pot, it's time for a new pot. Also, if you think you have overfertilized your plant, saturate the roots, watering thoroughly to flush out the fertilizer.

Also, make sure that the plant's leaves are not being scorched or burned in the sun; a blistering sun and insufficient water can lead to yellowing. Move the plant to a shadier spot to protect it from the sun's harsh rays.

Browning Leaves

If you see brown spots, this can indicate a disease like a fungus or bacteria. If you have brown edges or tips, it can result from too much aluminum sulfate added to the soil to change the color of the blooms. Your plant's roots may also be burning with too much or direct contact with fertilizer. Flush the soil with water to remove any extra fertilizer or aluminum sulfate salts.

  • How do you change the color of Bloomstruck flowers?

    The color of the flowers will range from reddish in alkaline soil to violet-blue in acidic soil. Add lime to the soil to achieve a more alkaline soil for more reddish blooms. If you want blue flowers, add aluminum sulfate to make acidic soil. For purple flowers, maintain a pH level between the two.

  • How long can Bloomstruck hydrangea live?

    Bloomstruck hydrangeas are fast-growers, and you can expect them to live for about 20 years.

  • Can Bloomstruck hydrangeas grow indoors?

    Bloomstruck hydrangeas can grow indoors. They need at least 4 hours of bright, indirect light every day. The soil needs to remain evenly moist during the growing season, never soggy. If the plant is drying out very quickly, it may be rootbound and need a new, larger container. Use filtered water to water your hydrangeas. Some municipal water plants may add lime to soften hard water. Lime can make the plant's soil alkaline and may inadvertently change the color of your flowers.

Article Sources
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