The enigmatic bond between Jack Frost and hydrangeas is a complex one, particularly in the Southern regions where Jack’s whimsical visits can be followed by a sudden surge of 80-degree warmth. Yet, fear not, for we’ve compiled a set of expert tips to help your beloved hydrangeas adapt to the impending chill of the first frost and freezing temperatures.
Spanning a vast expanse, the Southern United States sees a wide range of first frost dates, varying greatly with each USDA hardiness zone. While these dates are rooted in historical records, it’s crucial to be ready for an early or late frost in the microclimates within these zones. Generally, the Upper South experiences frost from October 19 to November 15; the Middle South from November 7 to 28; and the Lower South from November 25 to December 13.
Hydrangeas are particularly susceptible to autumnal frosts. New wood-blooming hydrangeas might still be in a state of growth in warmer zones, and an unexpected frost can lead to blackened, drooping leaves and stems. However, a single frost won’t spell the end for a robust plant. On the other hand, an unforeseen hard freeze can harm flower buds on old wood-blooming varieties, but with the right precautions, this can be avoided.
Once the hydrangea’s vibrant blooms begin to fade, the temptation to prune may arise. However, before you reach for the shears, it’s vital to identify the type of hydrangea in your garden. Timing is everything when it comes to pruning, as an ill-timed cut can result in a lack of blooms for the following year.
- New wood hydrangeas, including panicle and smooth varieties, produce blooms on new wood that emerges in spring. These should be pruned during their dormant phase in early winter. A light fall pruning to remove withered blooms is acceptable.
- Old wood hydrangeas, such as mophead and oakleaf varieties, set flower buds during their active summer growth. These should only be pruned immediately following flowering in spring and summer. Many horticulturists suggest ceasing pruning after August; fall pruning can diminish the number of flowers in the spring.
Not sure which type of hydrangea you’re nurturing? Take a look at the leaves before they shed their winter garb.
- Panicle hydrangea: Leaves shaped like arrows, with a pointed tip.
- Smooth hydrangea: Leaves large and heart-shaped.
- Oakleaf hydrangea: Leaves lobed, resembling oak leaves.
- Mophead hydrangea: Leaves large and oval-shaped.
As hydrangeas enter their dormant phase, there are several fall actions you can take to ensure their well-being through the winter months.
- Remove any damaged or diseased branches.
- Avoid pruning old wood-bloomers and wait until after the first frost to prune new-wood bloomers.
- Harvest dried blooms for indoor decor or leave them on the plant.
- Water thoroughly (the soil should be moist down to at least three inches) before the frost arrives.
- Apply two to three inches of mulch around the base of the plant to retain moisture and protect the roots. Keep the mulch about two inches away from the plant’s main stem, using organic materials like shredded leaves, pine straw, or pine bark.
For potted hydrangeas, water them approximately once a month to maintain soil moisture without creating a soggy environment. Water during the day and when temperatures are above freezing. Add a couple of layers of mulch to the soil surface to preserve moisture.
Hydrangeas sourced from florists typically require a winter indoors, as they are not suited to outdoor conditions. However, if you have a large container-grown hydrangea, it can remain outside. These are often so large that they require a forklift for relocation.
Container hydrangeas must undergo a natural dormancy period. In the South, they can typically overwinter in their current location unless there’s an unusual cold spell in the Upper South. In such cases, move the pots to a wind-protected spot or wrap them in a blanket of fleece, burlap, or bubble wrap.
With the unpredictable nature of Mother Nature, if frost is expected before the hydrangea leaves have fallen, you can safeguard their autumnal hues by covering the plants with a bedsheet or burlap before bedtime. Remove the coverings when temperatures rise the next morning. If the cold snap persists, cover them again at night.
Alternatively, you can embrace the end of the hydrangea season and anticipate the blooms of the following year. While frost may blacken and wilt some leaves, this should not impact the upcoming season’s blossoms.
