Proper hydrangea fall care is essential for maintaining the health of this popular shrub. If you want to see plenty of big, colorful blooms in the summer, then learning how to care for hydrangeas in the fall is a critical step. There are many different types of hydrangeas, and the care required for each different one varies slightly. However, there are some core fall hydrangea care practices you should follow regardless of which type you are growing. In this article, I’ll outline some of the most important late-season care tips for growing hydrangeas to ensure that next summer is bloom-filled and beautiful.
Why is proper hydrangea fall care important
Whether you’re growing mophead or bigleaf hydrangeas (Hydrangea macrophylla), smooth hydrangeas (Hydrangea arborescens), panicle hydrangeas (Hydrangea paniculata), or any other type, understanding how to care for these flowering shrubs in the fall and winter is crucial. If you prune them incorrectly or neglect to properly protect them from the elements, your hydrangea-growing efforts could be a failure.
Essentially, there are 7 practices to consider when it comes to hydrangea fall care. These steps include:
- Fertilizing (including to change the flower color)
- Providing weather protection
- Installing deer protection
- Care for container-grown hydrangeas
Each of the following sections of this article will focus on one of these 7 practices. Whether your favorite varieties are blue hydrangeas, or selections with pink flowers, white flowers, or the multi-colored blooms of the lacecap hydrangea, these instructions will be pertinent. Let’s start with the hydrangea fall care question of whether or not you should snip off the old spent flowers at the end of the growing season.
Should you cut off spent hydrangea flowers in the fall?
While this might sound like a tough question, you’ll be pleased to hear it does not have a complicated answer. Deadheading is the process of cutting off old blooms, and while this is a possible fall care task for hydrangeas, it is not an essential one.
Whether or not you remove dead hydrangea flowers is really a matter of personal choice. Removing dead hydrangea blooms will not impact the quality or size of the flowers the following growing season. I like the way the snow looks when it’s collected on a spent flower head after the leaves have fallen, but maybe you don’t. If you prefer a “neat and tidy” winter garden, then perhaps deadheading your hydrangea is a good idea. I find most of the dead flowers naturally fall off by the time spring arrives anyway, so I don’t bother going through the effort.
If you decide to deadhead your hydrangea in the fall, use a sharp pair of shears to trim the flower heads off of the plant. Remove just an inch or two of stem along with the flower. Do not cut the stems back any further than that or you could impact next year’s flower production (more about why this could happen in the next section).
Should you prune hydrangeas in the fall?
Beyond removing spent flowers, are there any other reasons you would want to prune hydrangea stems in the autumn? The short answer is no. No matter what type of hydrangea you’re growing, there’s no need to do any pruning as part of your hydrangea fall care. In fact, pruning in the autumn could remove flower buds for next year, depending on which variety of hydrangea you’re growing. Pruning at the wrong time can result in reduced blooms (or even no blooms at all).
There are two basic categories of hydrangeas:
- Those that bloom on old wood that was produced on the plant during the previous growing season. Examples of this would be bigleaf or mophead hydrangeas (H. macrophylla), lacecap, mountain (Hydrangea serrata), and oakleaf hydrangeas (Hydrangea quercifolia). These varieties are best pruned in summer, just after they flower (I prefer not to prune them at all).
- Those that bloom on new wood that was formed earlier in the same year the blooms are produced. Examples of this category would be peegee hydrangeas (H. paniculata ‘Grandiflora’), panicle hydrangeas, and smooth hydrangeas such as ‘Annabelle’. These selections are best pruned in the very early spring, before the new growth even emerges.
There is also a third, less formal, category known as repeat bloomers or continual bloomers. These hydrangea varieties bloom on both old wood and new wood. The popular Endless Summer hydrangea sits in this category, as does a handful of its cultivars, including ‘Blushing Bride’, ‘BloomStruck’, and ‘Summer Crush’. These varieties don’t need to be pruned at all, but if they are, late summer is a good time.
Many times gardeners cut off what they think are “dead” stems in the autumn, after the foliage has been damaged by a frost. Unfortunately, this practice could result in a plant that’s more prone to winter injury and produces fewer blooms. You could even be pruning off next year’s dormant flower buds. In short, do not prune hydrangeas in the fall.
Is fertilization an important part of hydrangea fall care?
Fertilizing hydrangeas is not an essential part of hydrangea fall care, but it is one you can tackle in the autumn if you have the time and energy to do so.
If you’re opting to use a natural granular fertilizer, applying it as part of your fall hydrangea care routine means that the nutrients will be processed by soil microbes over the winter months, making them available to fuel plant growth come spring. However, if you apply these fertilizers too early in the fall, you could unintentionally cause the plant to generate a lot of lush new growth that is prone to severe frost damage. Instead, wait until September or October to fertilize with natural granular fertilizers.
If you opt to use a rapidly available synthetic fertilizer, you are better off waiting until the spring to apply. Using these fertilizers when the plant is not in a state of active growth often leads to nutrient run-off and waste.
How to change hydrangea bloom color through fall fertilization
Some varieties of hydrangea (the mopheads [H. macrophylla], primarily) produce pink or blue blooms based on the soil’s pH. If you want to alter the bloom color by changing the pH, fall is a great time to initiate this practice. Essentially, the soil’s pH alters the availability of aluminum to the plant. Changing the pH of the soil dictates whether or not aluminum in the soil is accessible to the shrub.
- Blue flowers mean the soil is acidic, with a pH below about 5.5. Acidic soil means aluminum is more available and the result is blue flowers. To reduce your soil’s pH and encourage blue flowers, add ½ cup of pelletized sulfur for every 10 square feet of soil surface in the fall.
- Pink flowers mean the soil is basic, with a pH above 6. At that level, aluminum is tied up in the soil and not available to the plant. To increase your soil’s pH and encourage pink flowers, add 1 cup of dolomitic lime per 10 square feet of soil surface in the fall.
- Sometimes you’ll see a mophead hydrangea with both pink and blue flowers on it, or even with purple blooms. Typically, this means the pH is in the middle range between 5.5 and 6.0.
The process of changing hydrangea bloom color is best done in the autumn because it can take several months for an effective soil pH change to take place. Eventually, the soil will naturally revert to its original pH, so it will have to be a yearly practice. Remember that this does not work with all varieties of hydrangeas. Ones with “blue” or “pink” in the cultivar name will have that flower color regardless of the soil pH, and any species with white blooms will be unaffected by soil pH as well.
Do you need to mulch hydrangeas in the fall?
Adding a layer of mulch as part of your hydrangea fall care practice is a good idea, especially if you live in a cold climate. Surrounding the plant with a 2- to 3-inch-thick layer of shredded bark, arborist chips, or another mulch is great for maintaining consistent soil moisture and reducing weeds throughout the growing season. But, that same layer of mulch serves a different purpose in the fall and winter.
Fall mulching of hydrangeas leads to well-insulated roots that can better survive weather extremes and the ups and downs of freeze-thaw cycles. Do not over-apply mulch (2 to 3 inches is plenty), and do not pile it up against the plant’s base or trunk. Make a donut shape of mulch around your hydrangea. You can also use shredded fall leaves for this job.
How to protect hydrangeas from cold weather
If you live in a cold climate where some hydrangeas are not reliable bloomers, you may want to take extra steps to protect your plants through the winter. For mophead hydrangeas or other species that bloom on old wood, it’s essential that the buds not freeze out. Remember, the buds for next season’s blooms were formed the previous season. That means they are sitting dormant inside the existing stems on the plant all winter long. If you want to see blooms next summer, plan to protect the plants by providing an extra layer of insulation throughout the winter (the next section will outline the process of wrapping hydrangeas for the winter).
If you don’t want to go through the effort of having to provide added insulation, consider growing one of the many beautiful hydrangeas that bloom on new wood. There is no way their buds will freeze out because they won’t even form until the spring and midsummer.
Wrapping hydrangeas in the fall
Late winter and early spring are notorious for freezing out hydrangea buds on mophead hydrangeas. To insulate the shrubs, wrap them in landscape fabric, burlap, or heavy row cover in the fall. You can wrap the plant and tie or staple the fabric closed.
Alternatively, create a “box” around the plant by hammering four stakes in around the perimeter and stapling the fabric to the box. While you can make a “lid” for the box out of acrylic, Styrofoam, or another rigid material (see photo below), I leave the top open on mine. Snow collects inside the box and further insulates the plant. Plus, rainwater can easily reach the plant to keep it irrigated through the winter months. While this is not a must-do for hydrangea fall care, it will help protect the flower buds of mophead hydrangeas in very cold climates (USDA zones 5 and below). It is not a necessary practice for other types of hydrangeas.
Protecting hydrangeas from deer in the fall
In addition to protecting hydrangeas from the weather, you may also need to protect them from deer in the fall. Come late summer (August in my garden), the deer start to eat a lot in hopes of fattening up for the winter. Wrap hydrangeas in deer netting or spray them every two weeks with deer repellent spray. Here is an extensive article on how to keep deer from damaging your garden.
The deer also seem to be extra hungry in the early spring (March and April) when a lot of wild foods are not yet available to them. Be sure to check that your deer netting is still in place come spring. Often it’s crushed beneath snowfall or it collapses under heavy winter winds. Replace it if necessary.
How to care for containerized hydrangeas in fall and winter
If you grow hydrangeas in containers, there are a few additional items to consider for their fall care. While many hydrangea species are cold hardy, most do not tolerate extreme cold when their roots are not insulated by the earth. Container-grown hydrangeas have roots that are more prone to freezing out. To prevent this, follow one of these three paths:
- In the fall, surround the exterior of the pot with several layers of bubble wrap. Secure it with duct tape or twine. Move the pot to a protected spot (close to the house, for example, or next to a wall where it is protected from the wind). This adds an extra layer of insulation.
- Create a cylindrical cage of wire fencing around the outside of the pot that’s about one to two feet wider than the pot’s diameter. Stuff it full of straw or shredded leaves to help insulate the roots. Do not pile the straw or leaves on top of the plant; only around the pot.
- Move the pot into an attached but unheated garage or shed when the weather grows cold. One small window is all the light that’s needed. The plant will sit dormant until spring. Water it every 4 to 6 weeks. Make sure there is no standing water sitting in a saucer beneath the plant which could lead to root rot. When spring arrives, move the pot back outside.
The most important part of hydrangea fall care
If pressed for the most essential hydrangea fall care tip, I would say it is to not over-love them. I see more hydrangeas damaged by inappropriate fall pruning, over-fertilization, and over-mulching than anything else. Fall is an important time for hydrangea care, but it’s all-too-easy to overdo it. Be judicious about your hydrangea fall care practices and many beautiful blooms are sure to come.
For more about growing beautiful flowering shrubs, please visit the following articles:
- Panicle hydrangeas
- Unusual types of hydrangeas
- Flowering shrubs for shade
- Early blooming shrubs
- Are hydrangeas deer resistant?
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