Hydrangeas are a very popular landscape plant because they have such beautiful flowers, and they’re generally pretty easy to take care of. But there’s also a ton of confusion about hydrangea care and how to keep them looking their best. We’ve previously covered change-color hydrangeas, so we’ll take a look at pruning here.
While they’re all related, they do not all have the same growth and bloom patterns. Some hydrangeas change color based on pH; some hydrangeas bloom on fresh growth from this year called new wood, and some flower on the growth they put out last year called old wood. It all depends on the species of hydrangea, so it’s helpful to know what you have and keep the plant info card handy.
What Do Hydrangeas Look Like Before They Bloom?
Hydrangeas are a popular garden shrub known for their large, colorful blooms that brighten up the landscape. But before those showy blossoms emerge, there are some signs to look for that indicate your hydrangeas are getting ready to flower.
Flower Buds
The most obvious indicator that blooms are coming is the appearance of swelling flower buds along the stems and branches. On old wood varieties like bigleaf and oakleaf hydrangeas, these plump, gray-green buds form in late summer or fall before the plant flowers. They remain dormant through winter, then begin growing and expanding as temperatures warm in spring.
On new wood types like panicle and smooth hydrangeas, flower buds appear in spring on the new shoots that emerge. They are scattered along the fresh, green stems.
As the buds enlarge over several weeks, they take on a broccoli-like appearance before opening into flowers. Old wood hydrangeas bloom in spring and early summer while new wood varieties flower in summer and fall.
Leaf Growth
In tandem with the swelling buds, you’ll notice the leaves rapidly unfurling and expanding. Bright green foliage emerges from the tips of stems on old wood hydrangeas in early spring. New wood hydrangeas grow fresh leaves along the new stems that develop later in spring.
The expanding, vibrant foliage provides energy to support the pending blooms. Leaves reach their full size right before or as the flowers open. Lush leaves encourage larger, prolific blooms.
Changing Stem Flexibility
On old wood hydrangeas, the mature, woody stems that will bear the flowers become more pliable and flexible briefly before bloom time. The increased flexibility signals the aging branches are reviving in preparation for flowers. After bloom time, the stems will toughen up again.
On new wood varieties, the young, green stems that grow each spring are naturally supple and flexible when they first emerge. They remain so up until the flowers open later in summer.
Foliage Color Changes
Some hydrangea varieties temporarily change foliage color as the buds develop. Oakleaf and bigleaf hydrangeas may turn bronze, red, or purple during bud stage. This is caused by pigments that help protect the sensitive new growth. Once mature, the leaves turn back to green.
Expected Bloom Times
Knowing the normal bloom periods for different hydrangea types can provide clues about when those swelling buds will open into flowers:
- Bigleaf: June to July
- Oakleaf: May to July
- Climbing: June to July
- Panicle: June to September
- Smooth: June to September
- Mountain: May to August
By paying attention to these signs – plump buds, leaf growth, stem flexibility, and temporary foliage color changes – you can anticipate when your beloved hydrangeas will burst into their spectacular blooms. Proper care when they are preparing to flower will maximize their floral display.
Check Your Plant’s Hardiness Rating for Your Garden
If pruning isn’t your downfall, then check your shrub’s hardiness rating. Is it the right one for your growing zone? Keep in mind that the hardiness factor for hydrangeas can be confusing. The 2012 USDA Plant Hardiness guideline map is the standard by which gardeners can determine which plants are most likely to survive. The map is based on the average annual minimum winter temperature, divided into 10-degree F zones. The rating addresses a plant’s ability to SURVIVE low temperatures, i.e., will the roots make it? With hydrangeas, you need to go one step further to consider how well the STEMS survive. That’s the tricky part.
One way to figure out which plants will reliably flower in your zone is to ask your local garden center and the experienced gardeners you know. We all have stories of plants that were supposed to do fine and just didn’t. Hydrangeas are no exception.
Are Your Hydrangeas Blooming?
Every gardener I talk to, especially in the northeast and New England, is doing a happy dance this season: their hydrangeas are in full bloom. Despite temperature fluctuations, the sudden freezing temperatures of November 2019, and the wacky late spring weather we had (hailstorms, sub-freezing temps), these magnificent shrubs came through. All those dogs you have that haven’t been flowering are finally showing their colors. Or are they?
If your big leaf and mountain hydrangeas aren’t blooming this year, it’s time to do a quick Hydrangea Check Up.
First a little science…
Spring Hydrangea Care – 5 Tips for Happy Hydrangeas
FAQ
What plant is mistaken for a hydrangea?
Viburnum, also known as Chinese snowball or snowball viburnum, is a flowering bush or tree that looks almost identical to a white hydrangea except it’s easier …Jan 30, 2024