The BloomStruck® Bigleaf hydrangea is a popular cultivar in the Endless Summer® series of hydrangeas. It has been bred to bloom all summer, tolerates heat quite well, and is disease resistant, most notably to powdery mildew. Although there are several types of hydrangeas, the bigleaf hydrangea is unique because the soil pH level determines bloom color: very acidic soil results in blue blooms; soil that is less acidic results in purple blooms or blooms with a reddish hue.
BloomStruck hydrangeas produce large three to five-inch diameter, mophead-style flower heads with attractive reddish-purple branches and dark-green leaves. This fast-growing plant can be planted in spring or fall.
Hydrangeas are toxic to humans, cats, dogs, and horses.
|Common Names||BloomStruck hydrangea|
|Botanical Name||Hydrangea macrophylla 'P11HM-11'|
|Plant Type||Deciduous shrub|
|Mature Size||3-4 ft. tall, 4-5 ft. wide|
|Sun Exposure||Partial shade|
|Soil Type||Well-draining, moist|
|Soil pH||Acidic for blue blooms, alkaline for purple or red blooms|
|Flower Color||Blue, purple, red|
|Hardiness Zones||4-9 (USDA)|
|Native Area||Cultivar, no native range|
|Toxicity||Toxic to humans, toxic to dogs, cats, and horses|
BloomStruck Hydrangea Care
This plant requires little maintenance if you are not fussy about flower color. If you want to control flower color, you need to amend the soil to change its pH, raising or lowering the soil's acidity.
Pruning is usually not necessary other than removing dead, diseased, or winter-damaged branches. Remove branches that are rubbing against each other or are growing outward in a way that spoils the shrub's overall mounded shape.
BloomStruck hydrangeas are suitable for summertime hedges because they adorn the yard with excellent color when in bloom. You can also use BloomStruck hydrangeas as shrub borders along property lines, but because they are deciduous, they do not provide screening or privacy except in the summer and fall seasons.
BloomStruck hydrangeas grow best in part shade. In northern climates, hydrangeas can tolerate full sun if the soil remains evenly moist. Otherwise, grow them in filtered sun or partial shade.
Soil pH determines flower color. a pH below 5.5 produces blue flowers, a pH from 5.5 to 6.5 produces purple flowers, and a pH above 6.5 produces flowers in a reddish tone.
Enrich the soil (and improve its drainage simultaneously) by mixing in generous amounts of decomposed organic matter.
This shrub has average water needs when grown in partial shade, especially in the northernmost range of its hardiness. Average water means about one inch of water per week. But, water only when the soil is dry. Overwatering can inhibit blooming. Mulching will help the soil retain its moisture.
If the shrub appears to be droopy, wilted, and limp on a hot summer day, resist the temptation to turn on the hose; it does not need water. This behavior is the plant's way of protecting itself from the heat, and it will quickly perk up when temperatures cool down.
Temperature and Humidity
Endless Summer hydrangeas are hardy in USDA zones 4 through 9, however, they should be planted in a sheltered location below zone 6 to prevent winter damage. 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 the growing medium annually with compost or manure tea. Or, you can apply 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, use a fertilizer that contains a higher percentage of phosphorus. On a fertilizer bag, phosphorus is the middle number, so a fertilizer labeled 10-20-10 contains twice as much phosphorus as it does nitrogen and potassium.
If exploring slow-release granular fertilizers, choose a product where you see the term bloom booster because it probably contains a higher level of phosphorus. Too much nitrogen can result in lush foliage but fewer blooms.
Types of Endless Summer Hydrangeas
The Endless Summer brand includes BloomStruck and four other hydrangeas. They have been bred to produce buds and flower on old stems and the current year's new stems. They are valued for their ability to re-bloom all summer long, a behavior also known as remontant.
- 'The Original Bigleaf Hydrangea': Grows three to five feet tall and wide with pink or blue flowers
- 'Summer Crush'®': Plentiful, big raspberry red or purple blooms; 18 to 36 inches tall and wide
- 'Twist-n-Shout'®: Reblooming lacecap hydrangea; deep pink or periwinkle blue flowers; three to five 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; three to six feet tall and wide
BloomStruck hydrangeas bloom on both old and new growth, so technically, they do not require pruning at all. However, if you do prune them, do so in the 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. You should always remove stems that are dead, damaged, or diseased.
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.
It's important to know that other types of hydrangeas have varying pruning requirements depending upon when they set their buds for next year's flowers.
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. You can root cuttings in soil or water.
You'll need sterilized pruning snips, well-draining potting soil, an eight or 10-inch pot, rooting hormone, or a clear glass of water. Here's how to do it:
- Using a sterilized set of pruning snips, clip off a healthy six- to eight-inch stem that does not have flowers. Cut just below a leaf node (where leaves grow from the stem). Keep the topmost set of leaves on the stem, removing the remainder.
- Dip the cut-end in rooting hormone.
- Push the cut-end into a pot filled with damp potting soil.
- Cover the pot with a clear plastic bag and close it at the bottom. 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 soil by misting or watering frequently.
- Place the pot in a warm spot but not in direct sunlight.
- 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 feel resistance. Once it's developed roots, it's ready to transplant.
An alternative method is to place the cut end in a clear glass of filtered water placed in indirect light. Remove the bottom leaves up to the waterline. It might take much longer than rooting in soil—about two months or so. Replenish the water to maintain the same waterline every few days. Change the water every 10 to 14 days. Once the roots are one- to two- inches long, it's ready to pot in well-draining potting soil.
Potting and Repotting BloomStruck Hydrangea
Plants grown in containers need loose, pliable 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.
Terracotta pots work well because these porous pots absorb water, promoting a hospitable growing environment for hydrangeas. To repot a hydrangea, choose a pot that is one or two sizes larger than the current pot. Use a pot that has a wide, flat base because hydrangeas can get top-heavy. The flat base works best when placing your hydrangea outside because 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, some bigleaf hydrangeas will not bloom or will bloom poorly because of plunging temperatures, sudden or wide temperature fluctuations, icy conditions, or 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 those cold climates, protect your plants with shelter from harsh winds, which might be a burlap wrap or a circle of chicken wire filled with leaves or straw to a depth of eight- to 12-inches.
Here are some additional tasks to add to your Endless Summer hydrangea winter checklist :
- Stop fertilizing by mid-summer (end of July)
- Stop pruning in the fall
- Continue to water until frost
- Insulate roots with mulch
- Move container-grown plants to an unheated garage or shed
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 other species. You can reduce instances of powdery mildew through liberal spacing to promote better air circulation and by avoiding overhead watering.
How to Get BloomStruck Hydrangea to Bloom
Hydrangea flowers make good cut flowers, although they aren't fragrant. Since they rebloom all summer, you can safely cut some stems 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 overfertilization of the plant. You can deadhead after flowers fade to encourage new buds.
Common Problems With BloomStruck Hydrangea
Hydrangeas look like fussy plants; however, appearances are deceiving. This plant is relatively easy to care for if you plant it in the right location, control sun exposure, and maintain moist, well-draining soil.
If the plant looks droopy, wilted, and limp on a hot summer day, do not turn on the hose. It does not need water. This behavior is the plant's way of protecting itself from the sweltering temperatures, and it will quickly perk up when temperatures cool down.
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. If the soil is too soggy, let the soil dry out for a few days.
Plants grown in containers dry out more quickly than plants in the ground. If you have a potted plant, remove it from the container and look at its 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.
If you think you have overfertilized your plant, saturate the roots, watering thoroughly to flush out the fertilizer.
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.
If you see brown spots, this can indicate a fungal or bacterial disease. If the plant foliage exhibits brown edges or tips, it might be caused by too much aluminum sulfate added to the soil to change the color of the blooms.
Your plant's roots could have been burned with too much or direct contact with fertilizer. In that case, 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 acidify the 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.