As the warm days of summer give way to cooler September nights, it’s time to start thinking about preparing your garden for the colder months ahead.
For many of us, hydrangeas are the stars of our summer gardens, with their vibrant blooms and lush foliage.
But ensuring that your hydrangeas survive the winter requires a bit of foresight and preparation.
Over the years, I’ve learned that what you do in September can make all the difference when it comes to having healthy, blooming hydrangeas come spring.
Through trial and error, I’ve found the best techniques to help your hydrangeas weather the winter months.
In this guide, I’ll walk you through what you need to do in September to give your hydrangeas the best chance at surviving winter and thriving when warmer weather returns.
Know Your Hydrangea Type
The first thing you need to do before making any preparations is to identify what type of hydrangea you’re working with.
This is key because different types of hydrangeas have different care requirements, especially when it comes to winter survival.
Hydrangeas generally fall into one of four main types: Bigleaf hydrangea (Hydrangea macrophylla), Panicle hydrangea (Hydrangea paniculata), Smooth hydrangea (Hydrangea arborescens), and Oakleaf hydrangea (Hydrangea quercifolia).
Bigleaf hydrangeas, which include the popular mophead and lacecap varieties, are more susceptible to winter damage because they bloom on old wood.
These are the hydrangeas that most need protection over the winter, especially if you live in a colder climate.
Panicle and smooth hydrangeas, on the other hand, bloom on new wood, so they’re a bit hardier when it comes to surviving cold weather.
However, it’s still important to prepare them properly for winter to keep them healthy.
Knowing your hydrangea type will help you decide what steps to take in September to protect them.
I’ve learned this the hard way after pruning my Bigleaf hydrangeas at the wrong time and losing a whole season of blooms.
So, start by identifying your hydrangeas—it’ll save you a lot of trouble down the road.
Prune with Caution
September is not the time for heavy pruning if you have hydrangeas that bloom on old wood, like Bigleaf or Oakleaf hydrangeas.
These varieties set their flower buds for next year in late summer, so pruning too much or too late in the season can cut off those buds, leading to fewer or no blooms next year.
That said, light pruning is fine if you need to tidy up your plants.
I usually remove any dead or damaged branches and cut off any spent blooms (this is called deadheading), being careful not to cut too far down the stem.
In my experience, this light trimming helps keep the plant looking neat without disrupting its blooming potential for the next season.
If you’re dealing with Panicle or Smooth hydrangeas, which bloom on new wood, you can do a more thorough pruning in the fall if needed.
However, I usually wait until late winter or early spring to prune these types, as it encourages fresh growth when the weather warms up.
Clean Up the Base of the Plant
One of the most important things you can do in September is to clean up the area around the base of your hydrangeas.
Throughout the summer, leaves, old flowers, and other debris can accumulate at the base of the plant, creating a perfect environment for pests and diseases to thrive.
I make it a habit to clear out any dead plant material from around the base of my hydrangeas as part of my fall garden routine.
Using a small rake or your hands, gently remove any fallen leaves or spent blooms from the soil around the hydrangea.
This helps prevent fungal diseases from overwintering in the soil and keeps pests like slugs and snails from hiding out in your garden beds.
I’ve also found that cleaning up the base of the plant helps improve airflow, which is essential for reducing the risk of diseases like powdery mildew.
This simple task can go a long way toward ensuring your hydrangeas stay healthy through the colder months.
Water Deeply Before the Ground Freezes
Hydrangeas, like most plants, need water to survive the winter, but it’s all about timing.
In September, as temperatures start to cool down, it’s crucial to give your hydrangeas a few deep waterings before the ground freezes.
Doing this helps hydrate the roots and prepares the plant for the long, dry winter months ahead.
I usually aim to give my hydrangeas a deep soak once or twice a week in September, especially if we’ve had a dry end to the summer.
Watering deeply means soaking the soil down to about 12-18 inches, ensuring that the roots are well-hydrated.
However, it’s important to stop watering once the ground begins to freeze—overwatering at this stage can lead to root rot.
In my garden, I’ve found that keeping the soil consistently moist (but not soggy) in September helps the plant transition more smoothly into dormancy.
Healthy, hydrated roots are much more likely to survive the winter.
Add Mulch for Winter Protection
One of the best things you can do for your hydrangeas in September is to add a thick layer of mulch around the base of the plant.
Mulching helps insulate the roots and keeps the soil temperature more stable during the winter, protecting the plant from extreme cold and freezing-thawing cycles.
I usually apply a 3-4 inch layer of organic mulch, such as bark chips, straw, or shredded leaves, around the base of my hydrangeas.
The key is to cover the root zone without piling the mulch directly against the stems, as this can lead to rot.
Instead, leave a small gap around the base of the plant to allow for air circulation.
In colder climates, adding mulch can make the difference between your hydrangeas surviving the winter or suffering significant damage.
I’ve noticed that my Bigleaf hydrangeas, in particular, benefit from this added protection, as they’re more sensitive to cold weather.
Protect Against Frost and Cold Winds
If you live in an area with particularly harsh winters, you might want to take additional steps to protect your hydrangeas from frost and cold winds.
In my garden, I’ve used burlap or frost blankets to shield my hydrangeas, especially the more tender Bigleaf varieties.
To do this, I loosely wrap the plant with burlap or place a frost blanket over the top, securing it with stakes to keep it in place.
This helps protect the buds from being damaged by cold winds or heavy frost, which can dry out or kill the buds before spring.
It’s important not to wrap the plant too tightly, as good air circulation is still essential.
I’ve found that a loose cover provides the perfect balance between protecting the plant and allowing it to breathe.
Fertilize Lightly, If At All
By September, your hydrangeas are starting to prepare for dormancy, and encouraging too much new growth at this stage can do more harm than good.
I’ve found that it’s best to avoid heavy fertilizing in the fall, as it can stimulate tender new growth that won’t have time to harden off before the first frost.
If your hydrangeas need a little nutrient boost before winter, I recommend using a slow-release organic fertilizer or adding a light layer of compost around the base of the plant.
This provides the plant with a gentle feed without encouraging rapid growth.
In my own garden, I’ve noticed that over-fertilizing in September can lead to weaker plants that struggle to survive the winter.
Less is definitely more when it comes to fall fertilizing for hydrangeas.
Watch for Signs of Disease
September is also a good time to inspect your hydrangeas for any signs of disease or pest damage.
Common issues like powdery mildew, leaf spot, or fungal infections can spread quickly if not addressed before the plant goes dormant.
I always take the time to check the leaves, stems, and base of the plant for any signs of trouble.
If you spot any issues, prune off affected areas and dispose of them in the trash—don’t compost diseased material, as it can spread the problem to other plants.
In cases where I’ve had recurring issues with fungal diseases, I’ve found that applying a fungicide in September can help protect the plant through the fall and into winter.
Keeping your hydrangeas healthy as they head into dormancy is essential for ensuring they come back strong in the spring.
Consider Bringing Potted Hydrangeas Indoors
If you grow hydrangeas in containers, September is the time to start thinking about bringing them indoors or moving them to a sheltered spot.
Potted hydrangeas are more vulnerable to freezing temperatures because their roots don’t have the insulation that ground-planted hydrangeas do.
I’ve brought my potted hydrangeas into a cool, frost-free garage or basement for the winter, where they can rest without being exposed to the harsh outdoor conditions.
If you don’t have an indoor space for them, consider moving the containers to a more sheltered location, such as against the house or under a covered patio, where they’ll be protected from the worst of the winter weather.
Make sure to cut back on watering as the plant goes dormant, and be sure to bring them back out in early spring to enjoy the warmer weather and new growth.
Plan for Spring Success
Everything you do in September is about setting your hydrangeas up for success next spring.
By pruning carefully, cleaning up the area, and providing the right protection, you’re helping the plant conserve energy and stay healthy through the winter.
I’ve learned that September is a critical month for ensuring my hydrangeas survive the winter in top condition.
It’s all about timing and preparation, and the steps you take now will pay off when your hydrangeas burst into bloom next year.
Final Thoughts
Taking care of your hydrangeas in September is essential for ensuring their survival through the winter and preparing them for a healthy, vibrant spring.
By knowing your hydrangea type, pruning carefully, mulching, and protecting against frost, you’re giving your plants the best possible chance to thrive.
From personal experience, I can tell you that a little extra care in September can make all the difference when it comes to enjoying beautiful hydrangeas year after year.
Don’t wait until it’s too late—take the time this month to prepare your hydrangeas for winter, and you’ll be rewarded with stronger, healthier plants when the warmer weather returns.
Happy gardening!