The ‘Penny Mac’ Hydrangea is a popular cultivar of the Bigleaf Hydrangea, Hydrangea macrophylla, known for its large, rounded flower clusters called mopheads. This deciduous shrub is a reblooming variety, meaning it produces flowers on both the growth from the previous year (old wood) and the growth from the current season (new wood). This characteristic ensures a more reliable and prolonged display of color, often beginning in late spring and continuing through the summer and into the fall. The dependable flowering habit makes ‘Penny Mac’ an excellent choice for gardeners in cooler regions where late frosts might damage flower buds on standard old-wood-only hydrangeas.
Selecting the Site and Planting
Choosing the right location is essential for a thriving ‘Penny Mac’ Hydrangea. This shrub performs best in partial shade, receiving direct morning sun followed by dappled or full shade during the hot afternoon hours. Too much intense sun can scorch the large leaves and cause the plant to wilt quickly, especially during the peak of summer.
The soil must be rich, consistently moist, and well-draining. Hydrangeas cannot tolerate soggy conditions, which often leads to root rot. Before planting, amend the soil with organic matter, such as compost or peat moss, to improve both fertility and drainage. Dig the hole slightly wider than the root ball to allow the roots room to expand.
Ensure the top of the root ball is level with the surrounding soil surface before backfilling with the amended soil. Gently loosen the roots before planting to encourage outward growth. Water the newly planted shrub deeply to settle the soil and eliminate air pockets. Allow a minimum of four feet of space between plants to ensure good air circulation and accommodate their mature size of four to six feet in height and width.
Essential Routine Care
Consistent moisture is essential for ‘Penny Mac’ Hydrangea, as they are not drought-tolerant plants. Water deeply once or twice a week, especially during the first year of establishment and periods of hot, dry weather. Water at the base of the plant to keep the foliage dry, which helps prevent common fungal diseases like powdery mildew.
Apply a three-inch layer of organic mulch, such as shredded bark or compost, around the base of the plant. Mulch conserves soil moisture by slowing evaporation and helps keep the shallow root system cool. This practice also suppresses weed growth that would compete with the hydrangea for water and nutrients.
Fertilize in early spring as new growth begins, using a balanced, slow-release granular fertilizer. This formula provides a steady supply of nutrients throughout the growing season without encouraging rapid, weak growth. Avoid over-fertilizing, as too much nitrogen can promote foliage development at the expense of flower production.
Pruning for Reblooming Success
The ‘Penny Mac’ cultivar is a reblooming variety that sets flower buds on both old and new wood. This means the plant is much more forgiving of pruning mistakes or winter damage than traditional varieties that only bloom on old wood. Minimal pruning is generally required for this shrub, focusing mainly on maintenance rather than aggressive shaping.
The best time for necessary pruning is in late winter or very early spring, just before new growth starts. Remove any dead, damaged, or weak wood by cutting it back to the ground. Dead wood is identified by scratching the bark; if the wood beneath is brown instead of green, it should be removed.
Deadheading, or removing spent blooms, should be done immediately after the first major flush of flowers in early summer. This encourages the plant to produce new growth, generating subsequent blooms on the new wood later in the season. When deadheading, cut the spent flower stem back to the next healthy set of leaves or a pair of robust buds. Avoid heavy pruning to reduce size, as it can inadvertently remove developing flower buds.
Controlling Bloom Color
The flower color of ‘Penny Mac’ Hydrangea is influenced by the availability of aluminum in the soil, which is regulated by pH level. For blue blooms, the soil must be acidic (pH below 6.0), making aluminum readily available for absorption. To intensify blue color, apply aluminum sulfate to the soil in early spring and again in the fall.
To achieve pink blooms, the soil needs to be neutral to slightly alkaline (pH between 6.0 and 7.0). In this higher pH range, aluminum is unavailable to the plant, resulting in pink flowers. Garden lime is the most common amendment used to raise the soil pH and encourage pink coloration.
Altering the soil pH is a gradual process that may take several seasons of consistent applications to achieve a color shift. Apply soil amendments well in advance of the blooming season, such as in late autumn or early spring. Testing the soil pH is the most accurate way to determine the starting point and necessary application rates.