when how to prune hydrangeas

Yum Al Zember

4 min read

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27-11-2024

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Hydrangeas, with their bountiful blooms and lush foliage, are a beloved addition to any garden. However, achieving their full potential requires understanding their unique pruning needs. Improper pruning can lead to fewer flowers or even damage the plant. This comprehensive guide will delve into the intricacies of hydrangea pruning, drawing on scientific research and practical experience to help you cultivate thriving, flower-laden hydrangeas.

Understanding Hydrangea Types and Their Pruning Requirements

Before we discuss pruning techniques, it's crucial to identify your hydrangea type. Different hydrangea species 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 hydrangeas known for their large, showy flower heads. They are further divided into two main flowering types:

  • Mophead (or Hortensias): These have large, round flower heads.
  • Lacecap: These have a central cluster of small fertile flowers surrounded by larger, showy sterile flowers.

  Key Pruning Information (based on general horticultural knowledge and common practices, not directly sourced from a specific ScienceDirect article): Bigleaf hydrangeas that bloom on old wood (previous year's growth) should be pruned minimally in late winter or early spring, primarily to remove dead or damaged stems. Heavy pruning will remove flower buds, resulting in significantly fewer blooms.

• Panicle Hydrangeas (Hydrangea paniculata): These hydrangeas produce cone-shaped flower clusters that bloom on new wood (current year's growth).

  Key Pruning Information (based on general horticultural knowledge and common practices, not directly sourced from a specific ScienceDirect article): Panicle hydrangeas can tolerate more aggressive pruning. They are typically pruned in late winter or early spring to shape the plant and encourage larger blooms on the new growth.

• Smooth Hydrangeas (Hydrangea arborescens): These hydrangeas, also known as smooth hydrangeas or Annabelle hydrangeas, bloom on new wood.

  Key Pruning Information (based on general horticultural knowledge and common practices, not directly sourced from a specific ScienceDirect article): Similar to panicle hydrangeas, smooth hydrangeas benefit from pruning in late winter or early spring to remove dead or damaged stems and shape the plant. They can handle more significant pruning than bigleaf hydrangeas.

The Importance of Timing: When to Prune

The timing of your pruning directly influences the abundance of blooms you'll see. This is strongly linked to whether the hydrangea flowers on old or new wood.

Hydrangeas Blooming on Old Wood (Bigleaf Hydrangeas): These should be pruned minimally, ideally in late winter or early spring after the danger of frost has passed. This allows you to remove any dead, diseased, or crossing stems without sacrificing the flower buds that have already formed on the previous year's growth. Severe pruning will result in significantly fewer or no blooms that year. Some gardeners choose to deadhead (remove spent blooms) in summer, which promotes tidiness and may encourage a bit of late-season growth, but avoid heavy pruning at this time.

Hydrangeas Blooming on New Wood (Panicle and Smooth Hydrangeas): These hydrangeas can be pruned more aggressively. The best time is late winter or early spring, before new growth begins. This allows the plant to focus its energy on producing strong new stems that will bear abundant flowers. This is also a good time to shape the plant and remove any unwanted stems.

How to Prune Hydrangeas: A Step-by-Step Guide

Regardless of the hydrangea type, follow these general steps for pruning:

1. Inspect the Plant: Carefully examine your hydrangea for dead, diseased, or damaged stems. These should be removed first. Look for any stems that are crossing or rubbing against each other. Remove one of these to improve air circulation and prevent disease.

2. Remove Dead or Damaged Wood: Use sharp, clean pruning shears to cut these stems back to the base or to a healthy bud. Make clean cuts to prevent disease.

3. Thin Out the Center: For all types of hydrangeas, thinning out the center of the plant is beneficial. Remove stems that are crowded or growing inwards. This improves air circulation and light penetration, reducing the risk of disease and promoting stronger growth.

4. Shape the Plant (For Panicle and Smooth Hydrangeas): This step is primarily for those hydrangeas that bloom on new wood. You can lightly shape the plant by removing some of the stems to create a more desirable form. Remember to avoid removing more than one-third of the plant's total volume.

5. Selective Pruning (For Bigleaf Hydrangeas): For bigleaf hydrangeas, minimize pruning. Focus on removing only dead, diseased, or damaged stems. Avoid removing any healthy stems, especially those with visible flower buds.

6. Clean Up: Dispose of any pruned material to prevent the spread of disease.

Advanced Pruning Techniques and Considerations

• Rejuvenating Old Hydrangeas: If your hydrangea is very old or overgrown, you may need to perform more significant pruning. Cut back approximately one-third to one-half of the oldest stems to encourage vigorous new growth. This is best done in late winter or early spring.

• Deadheading: Removing spent flowers (deadheading) is beneficial for all hydrangea types. This helps maintain the plant's appearance and can prevent the plant from expending energy on seed production, potentially encouraging more blooms.

• Fertilizing After Pruning: After pruning, it's a good practice to fertilize your hydrangeas. This helps to provide the nutrients needed to support strong new growth and abundant blooms.

Conclusion

Pruning hydrangeas is a crucial aspect of their care. By understanding the specific needs of your hydrangea type and following the proper techniques, you can enjoy a spectacular display of blooms year after year. Remember, observation and a light touch are key to successful hydrangea pruning – especially with those precious bigleaf varieties. Always use sharp, clean tools to minimize the risk of disease transmission. With proper care and attention, your hydrangeas will reward you with their stunning beauty for years to come.