The ‘Endless Summer’ variety of bigleaf hydrangea, Hydrangea macrophylla, is a re-blooming cultivar that produces flowers on both old and new wood. This characteristic makes it resilient in colder climates where traditional hydrangeas often fail to flower. Despite this advanced breeding, gardeners frequently encounter issues, such as a lack of blooms or sickly foliage. Fortunately, most common problems are easily diagnosed and corrected with minor adjustments to care practices.
Why Your Hydrangea Won’t Bloom
The absence of flowers is the most frequent complaint. Diagnosis is required to determine if the failure is on the old wood, new wood, or both. The first bloom of the season relies on buds set on the old wood from the previous summer. This growth is susceptible to winter damage or improper handling.
Improper pruning is a common cause of bloom failure on old wood. Endless Summer hydrangeas require minimal pruning; never prune them after August or in the fall, as this removes the developing flower buds. Wait until early spring to assess the plant. Only remove wood that is clearly dead, dry, and brown, leaving all green-budded stems intact.
Winter kill can also eliminate the old wood buds, especially in colder zones, leading to a delayed or diminished first flush of flowers. While the plant should still produce blooms on new wood later in the season, this second set of blooms can be inhibited by insufficient light. Hydrangeas planted in deep shade often struggle to gather enough energy for prolific flower production.
To encourage maximum bloom production, site your hydrangea where it receives morning sun followed by afternoon shade, especially in warmer climates. If the plant is receiving too little light, consider trimming back dense overhead tree canopy or moving the plant to a location that receives at least three to four hours of direct morning sun. If winter damage occurred, allow the plant to push new growth from the base, which will produce the later summer blooms.
Solving Leaf and Water Stress Problems
Foliage problems often signal cultural issues related to hydration or nutrition. Wilting is common during the hottest part of a summer afternoon, as large leaves rapidly lose water through transpiration. If the plant revives overnight or after temperatures cool, it is exhibiting temporary heat stress and does not require immediate watering.
If wilting persists, the plant needs a deep, thorough soaking rather than a daily light sprinkle. Shallow watering encourages shallow root growth, making the plant more vulnerable to drought stress. Aim to keep the soil consistently moist, but not saturated. Apply water directly to the base of the plant, utilizing drip irrigation or a soaker hose.
Another common leaf problem is chlorosis, which presents as yellowing leaves with distinct dark green veins. This condition indicates an iron deficiency, often caused by the plant’s inability to absorb iron due to alkaline soil (pH above 6.5). This high pH causes a nutrient lock-out, preventing uptake even if iron is present.
To correct this, first perform a soil test to confirm the pH level. For a quick fix, apply a foliar spray or soil drench of chelated iron, which is immediately available to the plant roots. For long-term correction, you must lower the soil pH by incorporating amendments like elemental sulfur or ferrous sulfate, which makes the iron more accessible for absorption.
Identifying and Treating Pests and Diseases
Although resilient, Endless Summer hydrangeas can fall victim to specific pests and fungal diseases. One of the most common pest issues involves aphids, which are small, pear-shaped insects that feed on sap, causing new leaves to curl and distort. Spider mites thrive in hot, dry conditions and leave behind a fine webbing and tiny yellow or white spots, called stippling, on the leaves.
For both aphids and spider mites, the first line of defense is a strong jet of water from a hose directed at the undersides of the leaves, which can physically dislodge the pests. If the infestation is severe, a targeted application of insecticidal soap or horticultural oil can effectively control the population.
Fungal diseases are prevalent, particularly powdery mildew (a dusty white coating) and leaf spot (dark, circular spots). Both conditions are often caused by poor air circulation and excessive humidity.
To manage these diseases, focus on improving air flow by thinning overcrowded plants or ensuring adequate spacing during planting. Avoid overhead watering, as wet foliage encourages fungal spore germination; instead, water the soil directly. Remove and dispose of all infected leaves and use an approved organic fungicide, such as one containing neem oil, if the problem persists.
Seasonal Protection for Long-Term Health
Preventative care ensures the plant maintains the vigor needed for continuous blooming. Initial site selection is important; the ideal location provides shelter from intense midday and afternoon sun while still offering sufficient light for flower bud formation. In northern zones, the plant tolerates more sun, but in southern zones, dappled shade is necessary to prevent leaf scorch.
Proper mulching is a simple yet effective maintenance step that protects the root system and aids in moisture retention. Apply a two-to-three-inch layer of organic mulch, such as shredded bark or compost, around the base of the plant. Ensure the mulch does not directly touch the crown of the plant, as this can trap moisture and invite rot.
In colder climates, especially USDA Zones 4 and 5, winter protection for the buds on old wood is advisable to ensure the earliest spring bloom. Once the plant is dormant and temperatures are consistently below freezing, mound eight to twelve inches of insulating material, such as leaves or straw, over the crown of the plant. This practice shields the buds from extreme temperature fluctuations and harsh winter winds.