Spiraeas and Allies
What are they?
The species in this group are all shrubby members of the Rose Family (Rosaceae). They mostly have showy panicles made up of a large number of relatively small, pink or white, flowers.
Where are they found?
None of these species are native to the UK and all originate as garden ornamentals, occasionally being found where persisting from original plantings. They may appear on roadsides, rough ground, in hedgerows or in open, heathy or grassy places such as commons and suburban lanes. Most of these species are rare in the wider countryside but may often be encountered in parks or municipal plantings.
Identification
Some of the plants on this page can be tough to identify and it may require more than one visit to an individual plant to check a range of features, particularly amongst the sorbarias and the pink spiraeas. Details required can be seen in the individual species descriptions, but for the pink spiraeas can include leaf length and width plus details of marginal teeth, leaf veining and leaf hairiness. Details of flowers include size and shape of flower spikes and the shade of colour in pink-flowered plants. For the sorbarias, the best identification features lie in the fruits.
Note: there is much confusion over the English names for the spiraeas in this group, with the same names being variously used for a range of different species. Bridewort, Hardhack and Steeplebush get variously used for the pink-flowered species and bridal-wreath or Bridal-spray variously for the white species. I have tried here to take a concensus from a variety of sources, but the scientific names provide a more reliable baseline. It is probably also fair to say that a lot of pink-flowered plants sold through retail outlets are wrongly labelled.
As far as the pink-flowered spiraeas are concerned, many plants in the past were assumed to be S. salicifolia, until the presence of hybrids in the horticultural industry was better understood. At present, local botanists are working through known populations to check identifications, with many being reidentified as one or other of the hybrids, in particular, S. x pseudosalicifolia.
Confusing Bridewort Spiraea x pseudosalicifolia
A garden hybrid between S. salicifolia and S. douglasii. Widely recorded in the region in recent years, with most plants probably originating as garden throw-outs but some may have been planted in the past for pheasant cover. Flowers June to September. A spreading, suckering shrub, forming stands of stout, twiggy branches, to 1.5m in height. Flowers pink, carried in upright, branched spikes at the tips of the stems. Leaves 3-8cm long and 1-2.3cm wide, lanceolate, regularly toothed along the margins and with few hairs on the veins beneath.
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Billard's Bridewort Spiraea x billardii
A garden hybrid between S. alba and S. douglasii. Recorded at a small handful of locations across East Anglia. Flowers June to August. A spreading, suckering shrub, forming stands of stout, twiggy branches, to 1.5m in height. Flowers pale pink, carried in upright, branched spikes at the tips of the stems. Leaves at least 4cm long and at least 2cm wide, lanceolate to elliptic-ovate, rather coarsely toothed along the margins (except at the narrowed base) and with a good covering of hairs on the underside.
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Steeplebush Spiraea tomentosa
(Hardhack) Introduced from eastern North America as a garden ornamental. Recorded once in central Norfolk. Flowers July to September. A suckering shrub, forming stands of stout, twiggy branches covered in rusty hairs, to 1.5m in height. Flowers pink, carried in upright, branched spikes at the tips of the stems. Leaves 4-8cm long and 2-4cm wide, oblong-ovate, coursely serrate along the margins and with white, felty hairs beneath.
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Japanese Spiraea Spiraea japonica
Introduced from Japan. Planted as an amenity ornamental in parks and churchyards and occasionally recorded as a garden throw-out. Flowers June to September. A twiggy bush to 1.5m in height. Flowers pink, carried in flattened heads at the tops of the stems. Leaves 5-12cm long and 1-2.5cm wide, narrowly oblong, doubly serrate along the margins.
This species is often grown as the cultivar 'Goldflame', which has leaves opening with yellow, copper and red tones in the spring, later becoming greener.
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Van Houtte's Spiraea Spiraea x vanhouttei
A hybrid of garden origin. Planted as an amenity ornamental in parks and churchyards and occasionally recorded as a garden throw-out or where planted in hedges. Flowers May to June. A twiggy bush to 2m in height. Flowers appear in showy, rounded clusters along the lengths of the stems. Leaves 1.5-4cm long and 1.5-3cm wide, broadly ovate, coarsely toothed along the outer half of the margins.
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Bridal-spray Spiraea x arguta
A hybrid of garden origin. Planted as an amenity ornamental in parks and churchyards and occasionally recorded as a garden throw-out. Flowers May to June. A slender, twiggy bush to 2m in height with delicate, arching branches. Flowers appear in small, rounded clusters along the lengths of the stems. Leaves 1.5-4cm long and 0.5-1.5cm wide, broadly lanceolate, very finely toothed along the margins.
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Oceanspray Holodiscus discolor
Introduced from western North America as a garden ornamental. Recorded from Newmarket. Flowers May to August. A thinly-branched bush to 6m tall in the wild, but typically less in cultivation. Flowers creamy white, carried in weeping panicles, said to resemble the white crests of waves (hence the English name). Leaves somewhat resemble hairy hawthorn leaves.
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Ninebark Physocarpus opulifolius
Introduced from eastern North America as a garden ornamental. Grown as a garden plant and often included in amenity plantings in urban areas. Flowers May to June. A spreading shrub, eventually reaching 3m in height, but often less. Flowers white, in rounded heads, rather like those of hawthorn. Leaves with few hairs, mostly three-lobed. Older branches develop layers of flaking bark.
Plants in cultivation are usually yellow-leaved forms.
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