Annabelle is a cultivar of smooth hydrangea (Hydrangea arborescens) with white, ball shaped flower heads that can measure up to 30 cm across. It should not be looked after like a bigleaf hydrangea, and that is where most people go wrong. Annabelle sets its flowers on shoots that grow during the same season, and that decides both how you prune the shrub and why it flowers even after a winter that has frozen off everything above ground.
Annabelle flowers on new wood
Bigleaf hydrangea (Hydrangea macrophylla) lays down its flower buds as early as July and August the year before flowering. The buds sit on last year's wood all winter. If you cut the shrub down in spring you cut off the flowering, and if winter kills the shoots back, exactly the same thing happens. That is the explanation for why so many bigleaf hydrangeas stand green and flowerless year after year.
Annabelle works the other way round. The flower buds form on the shoots that come up during the current season. That has two consequences worth keeping apart. You can cut the shrub back as hard as you like in spring without sacrificing a single flower, and a winter that takes away everything above ground costs you no flowering, because the shrub builds new shoots from the base anyway.
The most common mistake is looking after Annabelle like a macrophylla. The owner does not dare to cut, the shrub goes thin and falls outwards, and the flower head shrinks year by year. If you want to read about the genus as a whole, we have an overview of hydrangeas.
How hard you cut decides the size of the flower head
Prune in March or early April, before the buds have swollen but after the hardest cold snaps. How far down you go is a choice, not a rule:
Hard, down to 20-30 cm above the ground: the shrub sends up few but strong shoots and the flower head can reach 30 cm across. At the same time the shoots stay thin in relation to the weight of the flower.
Light, taking off about a third of the height: you keep a framework of woody branches 40-60 cm tall. The heads get smaller but more numerous, and the stems carry them better because they branch out from old wood.
Whichever you choose: remove dead and broken branches right down at the base, and thin out the thinnest shoots that could not carry a head anyway. Last year's dry flower heads can stay on over winter and be cut off in the same round in spring.
When the flower head flops in the rain
A flower head of 25-30 cm soaks up rainwater like a sponge, and Annabelle's stems are soft by nature. After heavy rain in July, half the shrub lies out across the lawn. It can be controlled, but not with stakes alone.
Cut higher: a framework of 40-60 cm gives heads that sit on branched, woody shoots instead of on one single long shoot of the year. That is the measure with the greatest effect.
Hold back on the nitrogen: nitrogen rich fertiliser gives fast, soft growth that snaps easily. Feed once when the buds start to swell in spring and stop before the end of June. The balance between nitrogen, phosphorus and potassium is covered in the article on plant nutrition.
Put the support in on time: a support ring or three stakes with string around the shrub should be in place in May, when the shoots are 20-30 cm tall. If you add the support once the shrub is already down, you will never get the shape back.
Change cultivar: Incrediball (Hydrangea arborescens 'Abetwo') is a development of Annabelle with stiffer stems that carry the head upright without support. It grows to about 1.2-1.5 m tall and just as wide. If you want pink flowers instead, Invincibelle Spirit II (Hydrangea arborescens 'NCHA2') also has stiffer stems than Annabelle.
White stays white whatever the soil pH
The fact that hydrangeas change colour with the pH of the soil applies to bigleaf hydrangea and its close relative Hydrangea serrata. There the acidity controls how much aluminium the plant can take up, and the flower colour switches between blue in acid soil and pink in limy soil. Annabelle does none of this. White flowers lack the pigment that the whole reaction is built on, and you can add as much aluminium sulphate as you like without anything happening.
That affects where you put your money. Blueing products and ericaceous compost do nothing for the colour under an Annabelle. The shrub wants a soil that is neutral to slightly acid and holds moisture, and humus rich garden soil mixed with compost is plenty.
Position, soil and watering
Annabelle copes with both full sun and part shade, but in a position with sun from morning to evening it wilts almost daily in July. Morning sun with shade during the hours between 12 and 3 works best. The genus name Hydrangea is formed from the Greek words for water and vessel and actually refers to the shape of the seed capsule, but it fits the thirst of the plant just as well.
Reckon on around 25 mm of water a week during the growing season, given as a thorough soaking a couple of times a week instead of small splashes every day. Plant in well drained, humus rich soil and lay 5-8 cm of bark mulch or compost around the base. The mulch holds the moisture in and evens out the temperature around the shallow roots.
Hardiness and why Annabelle copes with cold winters
Smooth hydrangea belongs to eastern North America and is hardy on the American scale down to zone 3, that is winters with long spells of severe cold. In practice Annabelle can be grown across most of the UK and northern Europe, and the reason is the same one that governs the pruning. Because the flowers come on shoots of the year, it makes no difference if winter freezes the shrub back to ground level. It sends up new shoots from the base and flowers the same summer, from July and into September.
The first year after planting is the exception. The roots sit shallow and have not had time to establish. Lay on 5-10 cm of leaves or spruce branches in November and take the cover off in April once the ground has thawed.
Annabelle compared with panicle and bigleaf hydrangea
| Feature | Annabelle (H. arborescens) | Panicle hydrangea (H. paniculata) | Bigleaf hydrangea (H. macrophylla) |
|---|---|---|---|
| Flowers on | Shoots of the year | Shoots of the year | Last year's wood |
| Pruning in spring | Hard, down to 20-30 cm | Shorten by about a third | Only dead wood and spent flowers |
| Flowers after a winter that freezes the shrub back | Yes | Yes | No |
| Colour changes with soil pH | No, white stays white | No | Yes, blue in acid and pink in limy soil |
| Flower shape | Round heads up to 30 cm | Conical panicles | Balls or flat lacecaps |
Panicle hydrangea is looked after in almost the same way but grows considerably larger and takes more sun. It has its own walkthrough in the article on growing panicle hydrangea.
What you plant under the shrub
The hard spring pruning has a consequence that is rarely mentioned. From March to the end of May the spot stands more or less empty, because the shrub is down at 20-30 cm and the new shoots have not filled out. Solve it from below.
Plant bulbs in September or October in a ring 30-40 cm out from the stems. Daffodils, crocus and grape hyacinth finish flowering before the hydrangea has taken over the space, and their leaves have time to die back while the shrub starts to cast shade. We at Florea plant them in groups of 15-20 rather than scattered, because the effect shows more clearly when the shrub is freshly cut. You will find the selection among bulbs and tubers for autumn planting.
For the rest of the season, shade tolerant perennials do the same job closest to the ground. Flower heads cut in August, when they have started to shift from white towards green, dry well and hold their shape in a dried arrangement. If you want to build the whole bouquet yourself, there are seeds that are good for cutting.
Author: Emma Vogiatzi
Fact-checked by Erik Hoekstra
Last updated 2026-09-01