The ‘Blue Heaven’ Hydrangea (Hydrangea macrophylla ‘Blue Heaven’) offers a striking display of vibrant blue flowers, making it a highly sought-after plant. Its captivating color and substantial blooms contribute a bold visual element to various landscape designs. This cultivar is prized for its intense blue hues, transforming garden spaces with its presence.
Blue Heaven Hydrangea Characteristics
‘Blue Heaven’ is a deciduous shrub known for its large, bright blue flower heads. These “mophead” type blooms can appear from early summer through fall, providing an extended season of color. The foliage is a deep green, with glossy, serrated leaves that offer a rich backdrop to the vivid blossoms. This hydrangea typically grows to a mature size of about 4 to 6 feet tall and wide, forming a substantial, rounded shrub. Its bushy habit and sturdy stems support the large flower clusters, making it a robust addition to garden beds or as a standalone specimen.
Planting and General Care
Site Selection and Planting
Successful growth of ‘Blue Heaven’ Hydrangea begins with appropriate site selection. This variety thrives in partial sun, ideally with morning sun and afternoon shade, especially in hotter climates. Adequate light supports vibrant blooms, while protection from intense midday sun prevents stress.
The plant prefers well-draining, moist soil rich in organic matter. If your soil is sandy or heavy clay, incorporate organic compost during planting to improve structure and nutrient content. When planting, the top of the root ball should be level with the ground, and the plant should be thoroughly watered.
Watering
Consistent moisture is important for ‘Blue Heaven’ Hydrangea, especially during dry periods and as the plant establishes. While it prefers consistently moist soil, it does not tolerate waterlogging, which can lead to root issues. A general guideline is to provide about 1 inch of water per week throughout the growing season.
Deep watering, rather than frequent shallow sprinkles, encourages deeper root growth and overall plant health. Watering at the base of the plant helps prevent fungal diseases by keeping the foliage dry. Applying a layer of organic mulch around the plant can help retain soil moisture and regulate soil temperature.
Fertilizing
Fertilizing can support healthy growth and abundant blooms for ‘Blue Heaven’ Hydrangea. A balanced, slow-release fertilizer applied in early spring is often sufficient for mature plants. Some gardeners opt for a second application in mid-summer, particularly for younger plants or those in colder climates, to sustain blooms.
Fertilizers formulated for woody plants, such as those for roses, often work well. It is advisable to cease fertilization by late July to avoid encouraging tender new growth that could be vulnerable to winter damage. Apply granular fertilizers around the plant’s drip line and water thoroughly to aid in nutrient absorption.
Achieving and Maintaining Blue Color
The signature blue coloration of ‘Blue Heaven’ Hydrangea is directly influenced by soil chemistry, specifically aluminum availability in acidic conditions. For blue flowers, soil pH needs to be 6.0 or lower. If the soil is more alkaline (pH above 6.5), flowers may appear pink or purple, as aluminum becomes bound and unavailable.
To maintain blue blooms, aluminum must be present and accessible. Applying aluminum sulfate is a common method to lower soil pH and make aluminum available. Mix about 1/2 ounce (1 tablespoon) of aluminum sulfate per gallon of water and apply to the soil around the plant. Water the plant well before application to prevent root burn. Treatments often begin in early spring, with subsequent applications every 4 to 8 weeks to maintain acidity.
Elemental sulfur can also lower soil pH, though it acts more slowly. Organic amendments like pine needles, pine bark, peat moss, or coffee grounds contribute to soil acidification over time. Regular monitoring of soil pH with a test kit ensures levels remain within the acidic range (below 6.0) for blue flowers.
Pruning Blue Heaven Hydrangea
‘Blue Heaven’ Hydrangea is a Hydrangea macrophylla, a Bigleaf Hydrangea. While this type typically blooms on “old wood” (stems from the previous year), ‘Blue Heaven’ is a reblooming variety, producing flowers on both old and new wood for a prolonged season.
The best time to prune is immediately after its main flush of flowering in late summer. This allows the plant to develop new growth for next year’s flower buds. When pruning, remove spent flowers by cutting just below the flower heads. Also, remove any dead, damaged, or weak stems to maintain health and structure. Selectively prune up to one-quarter of the oldest or thickest stems down to the ground to encourage new, vigorous growth and improve air circulation.
Common Issues and Troubleshooting
‘Blue Heaven’ Hydrangea can encounter certain issues. Pests like aphids and spider mites may infest the plant. Aphids cause leaf distortion and sticky residue, while spider mites create fine webs on leaf undersides. A strong water spray can dislodge pests; insecticidal soaps or neem oil provide further control for significant infestations.
Fungal diseases like powdery mildew and leaf spot are also possible. Powdery mildew appears as a white coating on leaves, often in humid conditions, while leaf spots are discolored areas on foliage. Good air circulation through proper spacing and avoiding overhead watering helps prevent these issues. Promptly removing infected leaves limits disease spread.
Environmental stresses also impact hydrangeas. Wilting leaves, particularly during hot afternoons, often indicate the plant needs more water. Consistent watering and mulch can mitigate this. Yellowing leaves with green veins might suggest an iron deficiency, which can occur in alkaline soils, highlighting the importance of correct soil pH for nutrient availability.