Hydrangeas are popular garden shrubs known for their large, colorful blooms that can transform any outdoor space. Their success depends on providing the right environment and consistent, tailored care throughout the season. This guide provides actionable steps for establishing and maintaining these flowering plants to ensure you enjoy a spectacular display of their signature blossoms.
Establishing the Ideal Growing Environment
Most hydrangeas thrive in a spot that receives morning sun and is protected from the intense heat of the afternoon sun, especially in warmer climates. Too much direct sun can cause the leaves to scorch and the flowers to fade prematurely. Conversely, too much shade results in sparse blooms and weak, leggy growth.
Hydrangeas require rich, well-draining soil that remains consistently moist. Before planting, amend the native soil generously with organic matter, such as compost or well-rotted manure. This material improves soil structure for drainage and enhances moisture retention.
When planting, dig a hole two to three times wider than the root ball, but only as deep as the root ball itself. Set the top of the root ball level with the surrounding ground to prevent the stem from sitting too deep, which can lead to rot. After backfilling, apply a two to three-inch layer of organic mulch around the base of the plant. The mulch conserves soil moisture and regulates temperature, but it should not touch the main stem.
Routine Watering and Feeding Schedule
The name Hydrangea references the plant’s need for consistent moisture. Hydrangeas require deep, regular watering, especially during their first year while establishing root systems and during hot, dry weather. Aim to provide about one inch of water per week, delivered through deep soaks targeting the root zone.
Watering in the morning allows the foliage to dry out before nightfall, reducing the risk of fungal diseases. Avoid overhead watering; instead, use a soaker hose or water directly at the base of the plant. While wilting in the late afternoon is common, a plant that remains wilted in the morning requires immediate deep watering.
Hydrangeas benefit from a balanced, slow-release fertilizer applied in the spring as new growth begins. A second, lighter application in mid-summer can sustain blooming. Panicle and Oakleaf hydrangeas typically need two feedings, while Bigleaf hydrangeas may benefit from three light feedings. Avoid over-fertilizing with high-nitrogen formulas, as this promotes excessive leaf growth at the expense of flower production.
Pruning Methods Based on Hydrangea Type
Pruning correctly is essential, as the timing depends on whether the variety blooms on “old wood” or “new wood.” Incorrectly timed pruning is the primary reason hydrangeas fail to flower. Old wood bloomers include Bigleaf (Mophead and Lacecap), Oakleaf, and Mountain hydrangeas.
These varieties set flower buds on the previous year’s growth during late summer or fall. Pruning must be done immediately after the flowers fade in mid-summer, typically no later than July. Focus on minimal pruning: removing dead, weak, or crossing canes, and occasionally removing the oldest canes down to the ground for rejuvenation. Pruning these types in late winter or spring removes the developing flower buds, resulting in no blooms.
New wood bloomers, such as Panicle (like ‘Limelight’) and Smooth (like ‘Annabelle’), form their flower buds on the current season’s growth. These types can be pruned safely and heavily in late winter or early spring before new growth emerges. This timing allows gardeners to manage the plant’s size and shape without sacrificing the current year’s bloom. Deadheading spent flowers is appropriate for all types and can be done anytime to improve appearance.
Managing Bloom Color and Common Issues
The color of Bigleaf hydrangeas (Hydrangea macrophylla) is sensitive to the soil’s pH level. In acidic soil (low pH), aluminum is readily available for absorption, resulting in blue flowers. In alkaline soil (high pH), aluminum is unavailable, leading to pink or red blooms.
Gardeners can manipulate the color by amending the soil. Adding aluminum sulfate or elemental sulfur lowers the pH for blue flowers, while adding garden lime raises the pH for pink flowers. This color shift only works on pink or blue varieties; white-flowered cultivars are unaffected by pH.
A common concern is a lack of flowers, often caused by incorrect pruning time or late spring frost damage that kills overwintering buds. Poor blooming can also result from too much shade or inadequate water. Common pests, like aphids, and diseases, such as powdery mildew, are manageable. Improving air circulation helps prevent mildew, and insecticidal soap controls aphid infestations.