Hydrangea Macrophylla ‘Amethyst’: Large Rounded Clusters Of Double Or Single Florets

Hydrangea Macrophylla ‘Amethyst’: Large Gorgeous Rounded Clusters Of Double Or Single Florets

Hydrangea Macrophylla ‘Amethyst’

Photo Compliments Of Heartlover1717

Hydrangea macrophylla ‘Amethyst’ is a compact, deciduous hydrangea with, bushy, broadly ovate, toothed, veined, dark green leaves, and large gorgeous rounded clusters of double or single florets, blue, or light pink flowers in summer.

This big leaf hydrangea cultivar is part of the hortensia or mophead group (large sterile florets arranged in globular like panicles). It is a compact, deciduous shrub with a rounded habit. Mature height is typically 2 to 4 feet.  Ball-shaped flower clusters with a variable purple color are the ornamental highlight of ‘Amethyst’. Flowers are purplish pink to blue-violet.  In summer these shrubes produce mophead flower clusters plump with jagged-edge blossoms.  Florets (both double and single) in large, rounded, conical panicles (corymbs) bloom on terminal buds in July and last for up to two months. Sepals have serrated edges. Foliage is large, serrate, obovate to elliptic, lustrous, and medium to light green.

Bloom occurs on old and new wood for Hydrangea macrophylla ‘Amethyst’. Prune any time after flowering by cutting back flowering stems to a pair of healthy buds. It is easiest to see the difference between new and old wood in late winter or early spring. Prune out weak or winter-damaged stems in early spring. This hydrangea is hardy down to Zone 6 and with winter protection down to Zone 5 (use mulch), but may lose significant numbers of flower buds, or die to the ground in harsh winters, thus respectively impairing, or even totally destroying the bloom for the following year.

How To Make Your Hydrangea Macrophylla ‘Amethyst’ Thrive

This hydrangea thrives when it is grown in humus rich, well-drained soil in partial shade. It will tolerate full sun, but only if grown with constant moisture. Soil pH affects flower color (blue color in highly acidic soils and pink color in slightly acidic to alkaline soils). Add aluminum sulfate to soil to make flowers bluer or add lime to soil to make flowers pinker (add any such soil amendments to plant root zone in late autumn or early spring).

General Hydrangea Macrophylla ‘Amethyst’ Information

Pests and Diseases

No serious insect or disease problems. There is some susceptibility to bud blight, bacterial wilt, leaf spot, and mildew. Aphids are occasional visitors. Lack of winter hardiness is a significant problem in northern climates.


In early fall, choose cuttings that are at least 6 inches long, have no flower, and are new growth.

Garden Uses

This is an outstanding flowering shrub for informal hedges, partially shaded borders, and spacious foundation beds. Its blooms make wonderful, long-lasting cut flowers for your bouquets.

Quick Facts

  • Common Name: Big leaf hydrangea
  • Type: Deciduous shrub
  • Hardiness Zones: Zones 6 to 9
  • Height: 2 feet to 4 feet
  • Spread: 2 feet to 4 feet
  • Flower: Showy
  • Bloom Time: July to August
  • Bloom Description: Shell pink to pale lilac
  • Sun: Thrives in partial shade, can tolerate full sun
  • Water: Medium
  • Maintenance: Medium

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  1. Thanks for this very informative post, Charlie. Someone summer pruned a mophead hydrangea in the grounds here at York Rise and it looked as though it was dead all year. Having read this, I’ll go and have another look at it and see if I can see signs of life and maybe winter prune it!
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