Why Do Hydrangea Flowers Change Color?

One of the most exciting habits of some hydrangeas is the ability of the flowers to change color. This is not true of all hydrangeas, but most often seen in the mophead and lacecap cultivars of hydrangea macrophylla.

How to Change Hydrangea Flower Color?

This color change is due to the soil pH. Those with blue or pink flowers tend to be blue in acid soil conditions and pink in alkaline conditions. To get the best flower color, choose cultivars that give the best colors for the pH in question. White flowers will remain white regardless of soil pH. Hydrangea with blue flowers can be kept blue by growing the plants in acidic soil, or by acidifying soils. In soils where hydrangeas are not reliably blue, add aluminum sulfate. If the soil is very alkaline, this treatment may not work but can be very useful for container-grown plants. Use rainwater to water hydrangeas, since hard water can affect the flower color, turning blue flowers pink.  Boost red or pink flowers, by applying granular lime in winter

What Are Reblooming Hydrangea?

Reblooming hydrangeas are types that have the unique ability to flower on both old and new wood. Even if the buds are damaged by winter weather, the plant can still flower on wood it produces that season. Reblooming hydrangea varieties include the Endless Summer® series. These mophead and lacecap varieties, such as Twist and Shout® , Tuff Stuff™, and Tiny Tuff Stuff™ hydrangeas will bloom with little attention. Still, regular pruning encourages new growth, that can produce a better display.

Why Won’t My Hydrangea Bloom?

Hydrangea failing to bloom is a common dilemma for many of the older varieties of macrophylla and oakleaf hydrangeas. An unseasonable hard freeze or an improper pruning is typically the cause. These hydrangea types bloom on old wood. Winters with extreme freezing temperatures can injure unprotected flower buds. A pre-winter routine to protect these big leaf hydrangea blooms is to pile fallen tree leaves over the top of the plant for winter bud protection. Pruning out of season, too late in winter or too early in spring, will result in cutting off flower buds formed the previous season. 

Where to Plant Macrophylla Hydrangeas?

These shade-loving big leaf hydrangeas thrive in moist but well-drained soil, preferring morning sun. Avoid planting macrophylla hydrangea (mophead and lacecap types) in dry, sunny spots in exposed areas, where cold winds may damage young spring growth.

Can I Plant Hydrangeas in the Sun?

Uncle’s Idiot Proof hydrangeas are the panicle and arborescence (smooth) type hydrangea. These types are sun-lovers. While they prefer the sun, these hydrangeas will do just fine in partial shade, too. Both panicle and smooth hydrangeas, such as the white Annebelle, the Incrediball® and the red Invincebelle Ruby® hydrangea bloom late in summer on new wood. Unlike their famous shade-loving cousins, the macrophylla, or mop head hydrangea, which bloom on old wood. Hydrangea quercifolia, also known as Oakleaf hydrangeas, such as Alice and Ruby Slipper, are sun-loving hydrangea that flower on old wood growth.

When to Prune a Hydrangea?

Panicle and arborescence hydrangea are the perfect idiot-proof hydrangeas. Blooming late in summer on new wood, they require no special mulching or pruning techniques to see blooms the next year. If you forget to prune a paniculata hydrangea the previous season, no worries, shape them up during the winter thaw or the following spring.

The same is not valid for its cousins, the macrophylla hydrangeas. Mophead, lace-cap and oakleaf varieties of hydrangea bloom on old wood and should be pruned soon after blooms fade in late summer to early fall.

New Hydrangea Varieties

In the last few years, breeders have been developing many excellent varieties along with introducing new colors with bright whites, creams, lime green, and various shades of pink. Some of our most popular panicle hydrangeas are the Bobo, Quick Fire, and LimelightLimelight, with its huge football-shaped flowers, has almost revolutionized landscaping across America. Opening into light green, the blooms age to a bouquet of pink, red, and burgundy persisting through frost. Breeders have recently introduced a sibling Little Limelight growing three to five feet tall and wide. Proven Winner’s panicle hydrangea collection includes Quick Fire and a dwarf version Little Quick Fire. One of the first hydrangeas to bloom, the Quick Fire bloom emerges bright white and as blooms age; they change color to pink and finally red, giving the plant a multicolored effect in late summer and early fall.

What Is the Best Way to Plant Hydrangea?

When planting a hydrangea, use a balanced blend of Uncle’s Max Mix, mixed with native soil as backfill. Add organic matter after planting by using Uncle’s Black Magic peat compost as a top dressing. Consider using pine bark mulch to help soil acidity for mophead varieties.

Fertilize hydrangeas with Uncle’s Root Accelerator, low nitrogen plant starter, at planting.  Avoid feeding too often, with high nitrogen fertilizers, which can encourage excessive leaf growth, with plants less likely to develop flower buds and more at risk from winter damage.

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