How to Grow and Care for Penny Mac Hydrangea

penny mac hydrangea

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The Penny Mac hydrangea is a bigleaf cultivar known for its its large clumps of flowers and long season of bloom in summer, with buds forming continually all season. The pink flowers can be coaxed from pink to blue tones by making the soil more acidic. This hydrangea is long-lived and well-suited to partial shade conditions and moist soils. Its name in honor of Penny McHenry, founder of the American Hydrangea Society. McHenry received the plant as a gift in 1975, and propagated and shared it with fellow gardening enthusiasts.

Common Name  Penny Mac hydrangea 
Botanical Name  Hydrangea macrophylla 'Penny Mac' 
Family  Hydrangeaceae 
Plant Type  Deciduous shrub
Mature Size  4-6 ft. tall, 3-4 ft. wide
Sun Exposure  Partial sun 
Soil Type  Rich, loamy, well-drained
Soil pH  Alkaline soils produce pink flowers, acidic soils produce blue flowers 
Bloom Time  June to September
Flower Color  Pink, blue, purple 
Hardiness Zones 5-9 (USDA) 
Native Areas  Japan, East Asia
Toxicity Toxic to dogs, cats and horses
Pink mophead hydrangea

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Penny Mac Hydrangea Care

Penny Mac hydrangea is one of the hardiest available and provides flowers throughout the summer season, blooming on both old and new wood. It is generally low maintenance, but there are a few things to keep in mind to ensure proper care.

  • Plant your Penny Mac hydrangea in a spot where it will get part sun, part shade.
  • Use a rich garden soil mix with plenty of loam.
  • Water regularly, especially during dry weather.
  • Fertilize your hydrangea in the spring.


This plant grows best in a partial shade environment. Dappled shade is the perfect setting for the Penny Mac hydrangea. Morning sun is better than afternoon sun, which may get a bit too hot for the flowers in summertime.

Too much direct sunlight may scorch the leaves and dry out the blooms.


Penny Mac hydrangea prefers rich, loamy, well-draining soil. If you have clay soil, be sure to add soil amendments to improve drainage and nutrients.

As with other bigleaf hydrangeas, soil pH can affect the color of the flowers.

Alkaline soil will produce pink flowers; add lime and crushed eggshells to soil to get a pink flower. Acidic soil will produce blue flowers. Add aluminum sulfate to keep the flowers blue; you can also add acidifying soil amendments such as coffee grounds and pine needles.


Bigleaf hydrangeas like water, but too much water or improper watering can potentially lead to various diseases.

Water your Penny Mac hydrangea well after planting and continue to water regularly for 3 weeks until it is established. Be sure to water this shrub at its base, rather than overhead with a watering can, hose, or sprinkler.

Apply some mulch around the base of your hydrangea to help preserve and distribute moisture. Mulch will also protect the roots from being too dry or too wet.

Temperature and Humidity

Extremes in temperature or humidity can adversely affect your Penny Mac hydrangea. To counter excess humidity, don't water during times of rainfall, and use mulch to help distribute moisture.

In very hot, dry weather, be sure to water in early morning or at dusk.

Keep an eye on the shrub for signs of mildew or bacterial diseases in humid weather.


Timing is important when fertilizing a bigleaf hydrangea. Since a Penny Mac hydrangea blooms continuously in summer, too much fertilizer can interfere with blooming. Bigleaf hydrangeas display flowers more vigorously when they're not loaded up with nutrients.

A fast-release fertilizer should be applied only in spring. If applied in summer it might cause leaves to grow large but may slow flowering. Slow release fertilizers may be applied in spring also.

Follow package directions on the fertilizer you choose. Most fertilizers should be diluted before applying them at the base of the shrub; undiluted fertilizer can damage the roots.

Penny Mac vs. Endless Summer Hydrangeas

The main difference between the Penny Mac hydrangea and the Endless Summer cultivars is size: Penny Mac can grow up to 6 feet high and 4 feet wide, while the Endless Summer shrubs grow to a maximum of 4 feet high and 3 feet wide. Though both of these cultivars bloom throughout the summer, the Penny Mac's flowers start appearing in June, while Endless Summer hydrangea varieties such as Bloomstruck start flowering in July.

Pruning Penny Mac Hydrangea

The Penny Mac hydrangea should not need too much pruning. As a bigleaf hydrangea, it can be pruned in autumn, after flowers have gone dormant, or in early spring. When pruning in early spring, prune off the dead blooms from last season. Look carefully for buds and do not prune below the top bud formation. This will ensure you get the maximum amount of blooms for the season.

You can also prune immediately after flowering, down to the next pair of healthy buds, to keep it flowering through the season.

Propagating Penny Mac Hydrangea

The easiest way to propagate a Penny Mac hydrangea is using a division or cutting from a mature plant. Dividing or planting from a cutting is best done in spring to give the new plant a chance to get established.

Your bigleaf hydrangea should be at least 3 years old before you try dividing it. It should have at least two good-sized canes growing from the roots.

  1. Dig up the plant.
  2. At a natural junction point in the root ball, gently but firmly cut a well-rooted section.
  3. Plant it as you would a new hydrangea shrub.Water regularly, but be careful not to overwater.

You can also propagate a bigleaf hydrangea via cuttings.

  1. Cut a section with at least one node from a new growth shoot.
  2. Dip the cut edge in rooting hormone powder.
  3. Place the cutting in a container with moistened potting mix. It should form roots within a month.
  4. Once it has formed roots, transplant it to a large pot or into the garden.

Overwintering Penny Mac Hydrangea

Though hardy to USDA zone 5, occasionally macrophylla hydrangeas will fail to form buds if certain winter conditions damage them, such as an unusually long cold snap or an ice storm.

Your best bet is to give your Penny Mac hydrangea some extra winter protection. Add a layer of lightweight mulch (pine straw works well), and give the roots a bit of water if the winter is very dry. Wrap your shrub loosely in burlap to protect it from wind exposure and from ice formation on its branches.

Common Pests and Plant Diseases

Like other bigleaf hydrangeas, the Penny Mac is somewhat susceptible to pests and diseases. Aphids are a common problem, usually appearing on new leaf growth. They leave a sticky residue called honeydew that can often attract ants. Spray firmly with the hose to wash them away, or try an insecticidal soap or spray. Beneficial insects that eat aphids can also be used.

Other issues that can occur include leaf spot, bud blight, mildew, and bacterial wilt, all of which tend to show up during the summer blooming season.

  • Leaf spot is caused by a fungus that spreads in moist conditions. Remove all affected areas then look to prevention. You can prevent leaf spot by watering the plant at the base and not from overhead. Bud blight is also caused by a fungus (Botrytis cinerea), and treatment and prevention are the same as for leaf spot.
  • Powdery mildew also occurs in high humidity conditions, such as when hot summer days are followed by cool nights. Lack of air circulation (caused by having too much other plant growth near your hydrangea) and too much shade can also worsen this problem. Preventative measures will keep it at bay, but it can be treated with neem oil spray.
  • Bacterial wilt can spread in conditions of heavy rain followed by unusually hot temperatures. The flowers and portions of the leaves will turn brown. Remove any affected areas and, if possible, protect the plant from too much rain during a heatwave, and it may bounce back.

How to Get Penny Mac Hydrangea to Bloom

There's no point having a hydrangea if you don't make the most of its blooms. Here's what to know to encourage and care for Penny Mac blooms.

Penny Mac hydrangea Occasionally harsh winter weather conditions can affect spring buds on your big leaf hydrangea. If your Penny Mac misses an occasional year of bloom, this should not be cause for concern. But if it doesn't bloom two years in a row or more, there are some things to consider.

Bloom Months

The Penny Mac hydrangea normally blooms between June and September and will tend to bloom continuously from new bud formation in this time. For this reason it's important to avoid pruning it during the bloom season when buds are forming.

How Can I Encourage More Blooms?

If your hydrangea is not blooming vigorously, don't assume that adding fertilizer will help. Timing is important with fertilizer, as is the type of fertilizer used. Always read package directions. fast release fertilizer can be applied in spring. Applying fertilizer in summer is not recommended, as it may cause leaves to grow big, but stunt flower growth.

It prefers partial shade: if it's in a spot that's too shady or too sunny, you may want to consider relocating it to a better spot.

Why Isn't My Hydrangea Blooming This Year?

Your Penny Mac hydrangea may occasionally have a season where it doesn't produce any flowers. There are various reasons why a hydrangea is not blooming. Most commonly this happens when there is a late spring frost, which kills the buds. It may also happen if the shrub is pruned improperly, and buds are accidentally cut off. If you're very lucky, it may form some new buds in late summer, but it's possible it may miss a season of bloom. The only thing to do is wait, and give it proper care in the meantime.

  • How big does a Penny Mac hydrangea get?

    Penny Mac hydrangea can grow up to 6 feet tall and up to 4 feet wide.

  • How much sun does a Penny Mac hydrangea need?

    The Penny Mac hydrangea does best in a partial sun location. Morning sun is better than afternoon sun, especially if your summers tend to get hot.

  • Does Penny Mac hydrangea bloom on old wood?

    The Penny Mac hydrangea blooms on both old and new wood, which is one reason it continually forms buds through the summer.

Article Sources
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  1. Hydrangea. ASPCA