If you’re wondering how to prune bigleaf hydrangea, you’re not alone. These popular shrubs, with their iconic mophead or lacecap blooms, can confuse even experienced gardeners. The good news is that pruning them is straightforward once you know a few key facts. This easy step-by-step guide will walk you through the entire process, ensuring you get beautiful flowers year after year.
How to Prune Bigleaf Hydrangea
Before you make a single cut, it’s crucial to understand your plant. Bigleaf hydrangeas (Hydrangea macrophylla) bloom primarily on “old wood.” This means the flower buds for next summer are formed on the growth from the previous year. Pruning at the wrong time or too aggressively is the main reason for a lack of blooms. The goal of pruning is to maintain plant health, shape, and encourage robust flowering, not to control size drastically.
When is the Best Time to Prune?
Timing is everything with these hydrangeas. The safest window for pruning is immediately after the flowers fade in mid-to-late summer. Ideally, you should finish any pruning by early August.
- Pruning in summer gives the plant ample time to develop new growth that will mature and set bud for the following year.
- Avoid pruning in fall, winter, or spring. During these seasons, you risk cutting off the already-formed flower buds, resulting in few or no blooms.
- The only exception is for dead, damaged, or diseased wood, which you can remove any time you spot it.
Essential Tools You’ll Need
Using the right tools makes the job easier and healthier for your shrub. You’ll only need a couple of items:
- Bypass Pruners (Hand Shears): For most cuts on stems up to about 1/2 inch in diameter. Bypass pruners make a clean, scissor-like cut.
- Loppers: For thicker, older stems that are too large for hand pruners. Their long handles provide better leverage.
Always ensure your tools are sharp and clean. Wiping the blades with rubbing alcohol before you start helps prevent the spread of disease between plants.
Step-by-Step Pruning Instructions
Follow these steps in order for the best results. Remember, less is often more with bigleaf hydrangeas.
Step 1: Remove Spent Flowers (Deadheading)
Start by deadheading. Locate the first set of plump, healthy leaf buds below the old flower head. Make your cut about 1/2 inch above those buds. This neatens the plant’s appearance and can sometimes encourage a second flush of smaller blooms on reblooming varieties.
Step 2: Cut Out Dead and Damaged Wood
Next, scan the plant for any dead stems. These will be brittle, often lighter in color, and have no live buds. Cut them back to the base of the plant. Also remove any stems that are clearly damaged or rubbing against each other.
Step 3: Thin Out Old Stems (Optional)
For a mature, dense shrub, consider thinning. The goal is to improve air circulation and light penetration. Select a few of the oldest, thickest stems and cut them all the way down to the ground. Remove no more than about one-third of the total stems in a single year.
This practice revitalizes the plant over time, encouraging new, vigorous growth from the base. It’s not necessary to do this every year, but every few years can be beneficial.
Step 4: Shape the Plant Lightly
Finally, you can do light shaping. If a few stems are sticking out awkwardly or are much longer than the rest, you can trim them back to a joint or a set of buds that faces the direction you want new growth to go. Avoid giving the plant an overall “haircut”; this removes too many potential flower buds.
Special Case: Reblooming Hydrangeas
Many modern bigleaf hydrangeas are reblooming or “remontant” varieties (like the Endless Summer series). These flower on both old wood and new growth from the current season. This gives you more flexibility.
- You can prune them lightly in early spring to remove any winter-killed stem tips without sacrificing the entire season’s blooms.
- They still benefit from the primary summer pruning routine outlined above.
- If a harsh winter damages the old wood, they can still produce flowers on new wood later in the summer, which is their big advantage.
What Not to Do: Common Pruning Mistakes
Avoiding these errors will save you a lot of disappointment.
- Don’t Prune in Fall/Winter: This removes next year’s flower buds.
- Avoid Severe Cutting Back: Bigleaf hydrangeas do not respond well to being cut to the ground or heavily sheared. It will take years for them to recover and bloom again.
- Don’t Prune Just to Reduce Size: If your hydrangea has outgrown its space, consider transplanting it in fall or early spring rather than over-pruning. Choose a variety with a mature size that fits the location when planting new shrubs.
Aftercare Following Pruning
A little care after pruning supports strong regrowth. Water your hydrangea deeply if conditions are dry. Applying a layer of compost or a balanced, slow-release fertilizer around the base in early spring (not late summer) can provide nutrients for growth and bud formation. Mulching helps retain moisture and insulate the roots over winter, protecting those valuable buds.
FAQ: Your Bigleaf Hydrangea Pruning Questions Answered
Why didn’t my hydrangea bloom this year?
The most common causes are pruning at the wrong time (cutting off buds), winter cold killing the buds, or too much shade. Late spring frosts can also damage tender new bud growth.
Can I prune my hydrangea in spring?
For traditional bigleaf hydrangeas, it’s not recommended as you’ll cut off the buds. For reblooming types, you can do a light spring prune to remove dead stem tips only.
How do I prune a very old, overgrown hydrangea?
Renovate it gradually over three years. Each summer, remove one-third of the oldest, thickest stems at the base. This will encourage new growth while preserving some flowers each season.
My hydrangea got hit by a late frost. What should I do?
Wait until late spring or early summer to see where new growth emerges. Then, prune back the dead wood to just above those live, growing points. Reblooming varieties are especally good at recovering from this.
Is it okay to prune big leaf hydrangeas for shape?
Light shaping is fine immediately after summer blooming. Avoid heavy shearing. Always make your cuts just above a set of healthy leaves or buds.
Pruning bigleaf hydrangeas doesn’t need to be a source of anxiety. By following the simple rule of “prune right after summer blooming,” you’ll avoid the biggest pitfall. Remember, these are resilient plants. Even if you make a mistake one year, they’ll often bounce back with proper care. The key is to observe your plant, use sharp tools, and make clean cuts. With this knowledge, you can confidently keep your hydrangeas healthy and floriferous for many seasons to come.