when how to prune hydrangeas

Yum Al Zember

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27-11-2024

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When and How to Prune Hydrangeas: A Comprehensive Guide

Hydrangeas, with their bountiful blooms and lush foliage, are a beloved addition to any garden. However, achieving their full potential requires understanding their pruning needs. Improper pruning can result in fewer flowers or even damage to the plant. This guide will delve into the nuances of hydrangea pruning, clarifying the best times and techniques for various types. We'll draw upon information from scientific literature to provide accurate and practical advice, ensuring your hydrangeas thrive for years to come.

Understanding Hydrangea Types and Their Pruning Requirements

Before we discuss pruning techniques, it's crucial to identify your hydrangea type. Different types flower on different types of growth, significantly impacting when and how you should prune. The three main types are:

• Bigleaf Hydrangeas (Hydrangea macrophylla): These are the classic mophead and lacecap hydrangeas, known for their large, showy blooms. They are further divided into two flowering categories:

  • Mophead and Lacecap Hydrangeas (Flowering on Old Wood): These bloom on the previous year's growth (old wood). Incorrect pruning can drastically reduce flowering. [Source: (While specific Sciencedirect articles on precise pruning dates for Hydrangea macrophylla are scarce, general horticultural texts and studies on flowering mechanisms within the genus support the old wood/new wood distinction. Referencing a specific paper would be misleading without a direct correlation to pruning dates.)]

  • Panicle Hydrangeas (Flowering on New Wood): Though technically a separate type, panicle hydrangeas are often grouped with bigleaf types due to their similar appearance. They flower on the current year's growth (new wood) and tolerate more aggressive pruning. [Source: (Similar to the previous point, broad research on hydrangea flowering biology corroborates the new wood flowering characteristic. A specific Sciencedirect article directly linking pruning to this specific type would require extensive literature review beyond the scope of this prompt.)]

• Panicle Hydrangeas (Hydrangea paniculata): As mentioned above, these are distinct from bigleaf hydrangeas and bloom on new wood. This makes them much more tolerant of pruning. Their large, cone-shaped flower heads are a major draw for gardeners.

• Smooth Hydrangeas (Hydrangea arborescens): These are also known as Annabelle hydrangeas. They flower on new wood and can be pruned aggressively in late winter or early spring. [Source: (Again, comprehensive studies on precise pruning dates for Hydrangea arborescens are less readily available as standalone articles in Sciencedirect. The general understanding within horticultural literature and practice supports the new wood flowering and tolerance of hard pruning.)]

• Oakleaf Hydrangeas (Hydrangea quercifolia): These hydrangeas feature unique oak-shaped leaves and bloom on old wood. Pruning should be minimal and focus on removing dead or diseased stems.

Pruning Techniques and Timing:

The "when" of pruning is heavily influenced by the "which" – the type of hydrangea.

Hydrangeas that Flower on Old Wood (Bigleaf Mophead/Lacecap, Oakleaf):

• When: These should be pruned lightly, primarily in late summer or early fall after they have finished flowering. This allows the plant to set flower buds for the following year. Severe pruning at this time will drastically reduce blooms the next season.

• How: Remove any dead, diseased, or damaged stems. Thin out overcrowded branches to improve air circulation and sunlight penetration. Avoid major cuts, as these will remove next year's flower buds. You can lightly tip stems to encourage bushier growth, but be conservative.

Hydrangeas that Flower on New Wood (Panicle, Smooth, Annabelle):

• When: These hydrangeas can be pruned heavily in late winter or early spring, before new growth begins. This encourages robust new growth and abundant blooms.

• How: You can prune these back quite significantly, cutting stems to just a few inches above the ground if desired. Remove dead, damaged, or diseased stems. Thin out crowded branches to improve air circulation and sunlight penetration. The more you prune, the larger the individual flower heads will typically be.

Practical Examples and Considerations:

Let's say you have a mature bigleaf hydrangea that's become overgrown and leggy. You should prune it in late summer or early fall after flowering. Focus on removing dead branches and thinning out the interior to allow better light penetration, but avoid cutting back significantly.

On the other hand, if you have an Annabelle hydrangea that has become quite large, you can prune it back aggressively in late winter or early spring. You can even cut it to within a few inches of the ground, and it will still produce a profusion of blooms.

Beyond Basic Pruning:

• Deadheading: Regardless of the type, removing spent blooms (deadheading) encourages more flowers and keeps the plant looking tidy. This can be done throughout the growing season.

• Fertilizing: Proper fertilization supports healthy growth and abundant blooms. Use a fertilizer specifically formulated for hydrangeas, following package instructions.

• Watering: Consistent watering, especially during dry periods, is essential for healthy hydrangea growth.

• Pest and Disease Control: Monitor your hydrangeas for pests and diseases. Address any issues promptly to prevent significant damage.

Conclusion:

Pruning hydrangeas correctly is key to maximizing their beauty and longevity. Understanding the difference between old wood and new wood bloomers is critical for successful pruning. By following the guidelines outlined above and adjusting your approach to the specific type of hydrangea you are working with, you can ensure your hydrangeas thrive and reward you with their breathtaking blooms year after year. Remember to always use sharp, clean pruning shears to prevent the spread of disease. Happy gardening!