September is a transitional month in the garden. Many summer blooms are fading away while fall flowers are just beginning to put on their colorful displays. Hydrangeas are a popular flowering shrub that can change colors throughout the seasons. Knowing what to expect from hydrangea blooms in September can help you better appreciate their beautiful flowers.
The Color Progression of Hydrangeas
Hydrangeas go through striking color changes at different times of the year. In most cases, the blooms start out a fresh, bright white in spring. As summer arrives, the flowers often transition to pink, blue, or purple shades. This is due to changes in soil pH as well as the presence of aluminum in the soil. Some types of hydrangeas will remain white even as summer sets in.
By the time September rolls around, hydrangea blooms are preparing for the fall season. Blooms on the older wood or “old wood” of the shrub tend to transition to rich shades like deep pink, burgundy, green, or bronze. Meanwhile, flowers on the new wood or “new wood” remain vibrantly colorful in pink, purple, or blue hues. The variety and cultivar determines the exact colors you’ll see.
Common Hydrangea Types and September Bloom Colors
Let’s take a closer look at some of the most popular types of hydrangeas and the bloom colors you can expect to see in September:
Bigleaf Hydrangea (Hydrangea macrophylla)
| Cultivar | September Bloom Color |
|---|---|
| Nikko Blue | Vibrant blue fading lighter |
| Blushing Bride | Pink to purplish-pink |
| Endless Summer | Blue, purplish-pink, or bicolor |
The bigleaf hydrangea produces blooms on both old and new wood. Flowers on old wood transition to pink, burgundy, or green while new wood blooms remain colorful.
Smooth Hydrangea (Hydrangea arborescens)
| Cultivar | September Bloom Color |
|---|---|
| Annabelle | White, fading pale green |
| Incrediball | White, fading pale green |
| Invincibelle Spirit | Vivid pink all season |
The smooth hydrangea blooms on new wood so flowers remain white or pink well into fall.
Oakleaf Hydrangea (Hydrangea quercifolia)
| Cultivar | September Bloom Color |
|---|---|
| Snow Queen | White, fading light green |
| Alice | White, fading pink or purplish |
| Ruby Slippers | White, quickly turns deep pink |
The oakleaf hydrangea flowers on old wood so September blooms display rich fall tones.
Panicle Hydrangea (Hydrangea paniculata)
| Cultivar | September Bloom Color |
|---|---|
| Limelight | Lime green |
| Strawberry Sundae | Strawberry and cream |
| Pink Diamond | Deep pink |
| Little Lime | Chartreuse |
Panicle hydrangeas bloom on new wood so remain vivid even as autumn arrives.
What Impacts Hydrangea Color in Fall?
Several key factors influence the color of hydrangea blooms in September and beyond:
Flowering Habits
As mentioned, the flowers on old and new wood display different colors. Old wood blooms tend to transition to rich fall tones while new wood blooms stay bright.
Soil pH
The pH level of the soil impacts bigleaf hydrangeas in particular. More acidic soil (pH 5.5 and below) produces blue flowers. Alkaline soil (pH 7.0 and above) results in pink flowers.
Aluminum Availability
The presence of soluble aluminum in acidic soil helps bigleaf hydrangeas turn blue. As aluminum becomes less available late in the season, flowers fade lighter.
Cultivar Traits
Flower colors are also influenced by the cultivar. For example, the cultivar Nikko Blue stays vivid blue much longer than other bigleaf hydrangeas.
Weather
Cooler nighttime temperatures in September trigger the production of anthocyanins, pigments that create richer tones in hydrangea blooms.
Tips for Encouraging Beautiful Fall Blooms
With proper care, you can encourage hydrangeas to display their best fall colors in September and beyond:
- Leave spent blooms on the shrub since they continue absorbing nutrients back into the plant for next year’s flowers.
- Apply aluminum sulfate to acidic soils around bigleaf hydrangeas to intensify blue hues.
- Protect hydrangeas from harsh weather by providing winter protection if needed.
- Prune panicle and smooth hydrangeas in late winter or early spring before new growth emerges.
- Prune oakleaf and bigleaf hydrangeas immediately after flowering since they bloom on old wood.
- Water hydrangeas regularly throughout summer and early fall.
Conclusion
The colors of hydrangea blooms can vary considerably in September depending on the cultivar and growth habits. Bigleaf hydrangeas display the most striking color changes. Blooms on old wood transition from summer tones to rich hues of pink, burgundy, and green. Meanwhile, flowers on new wood remain vivid shades of blue, purple, or pink.
Smooth and panicle hydrangeas usually retain bright white or pink flowers well into fall since they bloom on new wood. Oakleaf hydrangeas produce white flowers on old wood that fade to pink or purplish-red.
With proper variety selection and care, hydrangeas can add beautiful late season interest to gardens with their diverse bloom colors. Appreciating how hydrangea colors change through the seasons can help you enhance their display in your own landscape.