Hydrangea arborescens
Smooth hydrangea
Common names: Wild hydrangea, Snowball hydrangea, Ball hydrangea, Woodland hydrangea
At a glance
- Light
- Partial shade
- Hardiness
- Hardy down to −30 °C
- Pruning
- Feb–Mar
- Flowering
- Jun–Sep
- Spacing
- 100 cm, rows 100 cm
- Water need
- High
Photo: H. Zell · CC BY-SA 3.0 · Source
This description was machine-translated.
Description
The smooth hydrangea, botanically Hydrangea arborescens, is a deciduous shrub native to eastern North America that grows 1 to 1.5 m tall and nearly as wide. From June to September it bears large, rounded flower heads up to 25 cm in diameter, which open pale green, then creamy white, and finally age to greenish to papery brown. In the wild form, small fertile flowers sit in the center of the flat flower clusters. In the widely grown cultivar 'Annabelle', nearly all flowers are sterile and form enormous balls. Unlike most bigleaf hydrangeas, it sets its flowers on shoots of the current year, so it blooms reliably even after harsh winters. It can be planted in beds in partial shade, in front of woody plants, in groups, or in large containers. Over the years it forms short runners and becomes broader.
Care instructions
Plant the smooth hydrangea in spring or autumn in a partly shaded spot with humus-rich, moist soil. It thrives in sun as long as the soil never dries out, with morning and evening sun being ideal and harsh midday sun less so. Space plants about 1 m apart. Water regularly and thoroughly, especially in summer. Drooping leaves at midday indicate it needs water. A mulch layer of leaves or bark compost helps retain soil moisture. Cut it back hard every year in late winter. Common mistakes are drought and insufficient pruning: the flowers are then too heavy for the thin stems and bend over after rain. More sturdy cultivars such as 'Incrediball' help with this.
The care notes were machine-translated from German.
Garden year
FloweringJun–Sep
Soil & site
Soil pH
Soil type
humus-rich, moist, loamy, nutrient-rich, well-drained
The smooth hydrangea loves humus-rich, nutrient-rich and evenly fresh soil that still lets water through. Loamy soils are ideal; on sand, work in plenty of compost. It tolerates slightly acidic to neutral soils and a little lime, but on very chalky soil the foliage turns pale. Waterlogging harms it too, yet in summer the soil must never dry out.
Feeding
Heavy feeder
Months
Mar, Jun
The smooth hydrangea produces many new shoots and large flower balls every year, so it has a high nutrient requirement. In March, when growth begins, work mature compost and horn shavings shallowly around the shrub. In June, give organic fertiliser once more, and then no more, so that the shoots can ripen before winter. In a container, give liquid fertiliser for flowering plants every two weeks until early summer.
Pruning
The smooth hydrangea flowers on new shoots, so cut it back hard every year in February or March. Shorten all shoots to about 20 to 30 cm above the ground or to two or three pairs of buds. This produces strong shoots with large flowers that do not flop over. The less you cut, the taller the shrub grows, but the stems become thinner and bend under the flower balls. Also remove weak, thin shoots completely.
Overwintering
The smooth hydrangea is fully hardy and needs no protection in the bed. Because it flowers on the shoots of the current year, flowering does not fail even after severe winters. Only late frost can damage the fresh growth, but it then sprouts again. Leave the dried flower balls standing over winter; they look lovely with hoar frost, and cut them off only in late winter. In a container, put the pot against a sheltered wall and wrap it in horticultural fleece so that the root ball does not freeze through.
Propagation
Methods
- Cuttings
- Division
The easiest way to propagate the smooth hydrangea is by division: in spring or autumn, dig up the shrub, divide it with a spade into pieces with roots and shoots and replant them straight away. Suckers with their own roots can simply be cut off in spring. Cuttings work in June and July: take 10 to 15 cm long, non-flowering shoot tips, remove the lower leaves, cut the large leaves in half and insert them into loose seed compost. Kept bright, warm and moist, they root after a few weeks.
For your garden
Grow Smooth hydrangea yourself
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