How To Grow And Care For 'Pistachio' Hydrangea

Kaleidoscopic blooms that can't help but steal the show.

The reigning queen of Southern landscaping, hydrangeas are synonymous with warm weather and bright summer days. These beautiful blooms stand up to the region's relentless heat and humidity, flaunting their beautiful blue, white, and pink flowers.

While classic hydrangea hues will always hold a special place in our gardens, we can't help but delight in a rebloomer that boasts a new shade. This season, we've got our eye on the showy 'Pistachio' hydrangea (Hydrangea macrophylla 'Horwack'). This eye-catching dwarf hydrangea packs a colorful punch into a compact shrub with multi-color blooms that last from spring until fall. Radiant chartreuse green and hot pink flowers will bring your landscape alive and demand a double take from passersby. Plant one, and you'll see what we mean. While beautiful, hydrangea plants are toxic to people and pets, so choose their planting location carefully.

Pistachio Hydrangea
Getty Images

Plant Attributes

Plant Attributes
 Common Name:  'Pistachio' Hydrangea, 'Horwack' Hydrangea
 Botanical Name:  Hydrangea macrophylla 'Pistachio'
 Family:  Hydrangeaceae
 Plant Type:  Perennial, Shrub
 Mature Size:  2-3 ft. tall, 3-5 ft. wide
 Sun Exposure:  Full, Partial
 Soil Type:  Moist, Well-drained, Rich
 Soil pH:  Acidic to Alkaline (5.0 to 8.0), depending on color preference
 Bloom Time:  Spring, Summer, Fall
 Flower Color:  Pink, Green
 Hardiness Zones:  Zones 5-9 (USDA)
 Native Area:  Asia
 Toxicity:  toxic to dogs, toxic to cats, toxic to pets, toxic to people

'Pistachio' Hydrangeas Care

'Pistachio' hydrangeas are versatile shrubs that thrive in garden bed groups or containers in Zones 5-9. They love morning sun and afternoon shade, so consider planting on the eastern side of your house to ensure they're nice and shaded in the heat of the day. With a mature height of two to three feet and a width of three to four feet, their modest size makes them an excellent fit for snug, shaded sections of your garden.

They do best in moist, well-drained soil and benefit from a slow-release fertilizer in the spring before the leaves begin to bud. Like most hydrangeas, this variety may need supplemental water in extreme summer heat or periods of drought.


'Pistachio' hydrangeas grow best in full morning sun and afternoon shade. Once established, these plants are relatively heat-tolerant. Areas with more sun exposure will require more frequent watering.


Hydrangeas grow best in moist, fertile soils that are well-draining. While tolerant and adaptable to many soil conditions, the pH levels will impact the bloom's coloring.


Provide consistent watering for moist soil, especially during the growing season. Hydrangeas are relatively drought-tolerant once established, but adding organic mulch to help retain moisture and assist with draining will help. Water once the top few inches of soil are dry.

Temperature and Humidity

Hydrangeas require high humidity levels as the foliage will turn brown in dry conditions. These plants thrive in hot Southern climates. Protect hydrangeas from harsh weather conditions, including providing shelter or covering for plants throughout the winter.


Add a slow-release fertilizer in the spring. Avoid fertilizer high in nitrogen as it will promote foliage growth instead of flower blooms. Organic compost can help retain soil moisture.

Types of Hydrangea macrophylla

The 'Pistachio' hydrangea is only one variety of this stunning blooming shrub that thrives in the South. Here are some Hydrangea macrophylla to know:

  • Bigleaf Hydrangeas (H. macrophylla): Also known as French hydrangeas, these shrubs bloom in late spring or early summer. These shrubs' flowers are susceptible to changing colors with soil pH shifts.
  • Mountain Hydrangea (Hydrangea serrata): Similar to bigleaf hydrangeas in appearance, this type produces blooms in a variety of colors, including pink, blue, and cream.
  • Oakleaf Hydrangea (Hydrangea quercifolia): Native to North America, this hydrangea variety produces foliage that resembles oak trees.


Since the 'Pistachio' hydrangea is a reblooming variety that flowers on both new and old wood, little pruning is required. This hydrangea is also a reliable bloomer, even after severe winters. Pruning typically requires removing damaged or diseased branches in early spring.

Propagating 'Pistachio' Hydrangeas

As a patented plant, propagating hydrangeas would infringe the copyright laws. Purchasing new, mature 'Pistachio' hydrangeas to plant is the only way to grow more shrubs safely.

Potting and Repotting 'Pistachio' Hydrangeas

As a compact plant, 'Pistachio' hydrangeas grow well in containers with well-draining soil and air circulation. Add perlite or peat moss to potting soil in the spring to prepare containers for transplanted hydrangeas once they emerge from dormancy. Choose a container at least two times bigger than the existing pot so the hydrangea's roots can establish and support the large blooms.


To prepare hydrangeas for winter, water deeply a few times throughout the fall to prepare the roots for dormancy. The only pruning required is to remove dead and damaged branches to make room for healthy, new growth and allow plenty of air circulation. Adding a thick layer of mulch near the plant's base will help protect the roots. Try an organic matter such as straw, marsh hay, or fallen leaves. If you live in a region that experiences large temperature fluctuations, adding a burlap or cloth covering—held in place with garden stakes—over the plant will protect it. 

Move potted hydrangeas indoors to a cool location—such as a garage or basement—to protect them from harsh winter winters and freezing temperatures. Potted hydrangeas will still experience dormancy and require watering throughout the winter to help keep the roots moist. 

Common Pests & Plant Diseases

Hydrangeas are relatively pest-free and disease-resistant. Some pests will attack hydrangeas, especially during the hot temperatures in the summer. Common pests that attack hydrangeas include aphids, Japanese beetles, and spider mites. If the issue persists, spray the plants with a water hose, or use insecticidal soap or neem oil. 

The diseases that impact hydrangeas include bud blight, bacterial wilt, leaf spots, and powdery mildew. Provide plants with plenty of air circulation, water the base of the plant instead of the top, and provide well-draining soil to help prevent these problems from developing.

How to Get 'Pistachio' Hydrangeas to Bloom

These kaleidoscopic hydrangeas are reliable bloomers, blooming on new and old wood. If a hydrangea is not blooming, fluctuating temperature conditions or frost exposure might be the cause. Improper care and overfertilization can also prevent hydrangeas from blooming. Deadheading can help encourage a second showing.

Common Problems With 'Pistachio' Hydrangeas

Hydrangeas are relatively problem-free plants. While these easy-to-maintain flowering shrubs do not have a lot of issues, there are still some things to know:

Leaves Turning Black/Brown

Several diseases that impact hydrangeas can cause the foliage to turn brown. Rust will first emerge on the underside of the foliage, appearing as orange-hued spots, which will eventually spread. Prune diseased branches or treat the rust with a fungicide. A second fungus that impacts hydrangeas includes leaf spots, which will present as small spots on the foliage. Leaf spots are more likely to appear on hydrangeas that are overly saturated with wet foliage. Water the base of the plant to help prevent this fungus from developing. Finally, anthracnose is a disease that causes cankers to form on stems and branches. Stop these fungal spores from spreading by removing the diseased branches. Make sure to use sterile gardening equipment and clean it after use.

Leaves Turning Yellow

Overwatering and nutrient deficiencies, typically iron, cause yellowing leaves on hydrangeas. Insufficient sun exposure can also cause hydrangea leaves to turn yellow. Maintain proper care and adjust the soil's pH with fertilizer. A mulch, such as pine bark, can help retain moisture and provide plenty of drainage.

Frequently Asked Questions

  • Can 'Pistachio' Hydrangeas Grow Indoors?

    Hydrangeas can grow indoors if given bright, indirect sun exposure. Use a well-draining container and fertilize weekly during the growing season.

  • How long can 'Pistachio' Hydrangeas live?

    In ideal conditions, hydrangea shrubs can live for 20 to 50 years. Proper care includes partial to full sun exposure and nutrient-rich, moist, and well-draining soil.

Was this page helpful?
Related Articles