Halesia are also known as silverbells or snowdrop trees because of their lovely pendent white flowers. After the flowers come distinctive winged fruits that persist into winter, making them a real feature.
Originally considered to be a genus of four-to-five species, those pesky scientists have looked at the genus again and decided that there are in fact only three species of Halesia. The reclassification states that there are two species in North America, H. diptera and H. carolina, which takes in the formerly distinct species H. monticola and H. tetraptera. Then there is the Chinese species H. macgregorii.
They are all deciduous small trees or shrubs, ranging between 3m and 15m tall in cultivation, though in the wild some specimens have been known to reach 30m. They share the pendent bell-shaped flowers. Most are pure white, hence the snowdrop name, and a few have a rosy pink tinge to them. They hang on slender stalks in clusters or short racemes, giving a massed effect in the spring.
The leaves unfurl with the flowers or sometimes afterwards. In autumn, after hot conditions they can turn a nice buttery shade of yellow, though it is not always a dramatic display and they fall quickly. The winged fruits are attractive, graduating from an initial bright green to tan or dark red/brown. They continue to hang from the branches throughout the winter, adding interest.
H. carolina, the best-known species, is a large group because of the subsuming of formerly distinct species such as the mountain silverbell, H. monticola, under its umbrella. This has led to a certain degree of confusion in the trade.
If we stick to the RHS terminology, there is H. carolina, with subgroups Vestita Group Award of Garden Merit (AGM) — a fast-growing tree, often with pink-tinged bell-shaped flowers — and Monticola Group, which has larger leaves and flowers.
H. diptera, the other American species, stands out for having two- rather than four-winged fruit. The Chinese silverbell, H. macgregorii, is rarely seen in gardens. It is the smallest of the species, with an upright habit and small, tubular white flowers.
The native habitat for Halesia is beside streams or as part of the understorey in mountain woodland, so they prefer a moist but well-drained, deep, humus-rich soil. It needs to be neutral to acidic too — planting in alkaline soils will lead to chlorosis. Aspect can be sun or partial shade.
It is best to use Halesia as a specimen tree in a mixed or woodland border, ideally against an evergreen backdrop to allow the white flowers to stand out best. They are also effective in small group plantings. Underplant with bulbs to increase the seasonal interest.
What the specialists say
James Harris, owner, Mallet Court Nursery, Somerset
"Halesia, or silverbell, as the Americans call it, is justifiably a very popular garden tree with masses of pure-white pendent flowers in summer. Halesia is a member of Styracaceae and is named after the clergyman and scientist Stephen Hales. The name is often mispronounced.
"It was first proposed that there were four species, three in the USA and one in China. A recent study by the Californian Academy of Sciences has concluded that there are only two species in North America, H. carolina and H. diptera.
H. carolina is now treated as a single taxon that subsumes H. tetraptera and H. monticola. I think that the naming of the silverbells will be confused for some time.
"H. carolina has the potential to become a large tree and can grow to 50 feet, whilst H. monticola — the mountain silverbell — is a smaller tree but has larger flowers and fruits. The silverbells prefer a moist but well-drained, lime-free soil. I have not experienced any problems with Halesia, nor any diseases.
"We offer H. carolina and H. monticola at our nursery, and usually have a good demand, but this winter orders have been fewer. We also offer the Chinese species H. macgregorii, which we introduced a few years ago. It is another very attractive silverbell with creamy white flowers. Here we usually call it the snowdrop tree."
Robert Player, proprietor, Garden Associates, central London/Hertfordshire
"Why oh why are these trees or really most of the Styrax family not more widely planted? Nurseries are starting to stock them on a more regular basis but their potential and elegant beauty are being missed.
"In central London I grow the snowdrop tree, the snowbell tree and the epaulette tree, all flowering at slightly different times. To the botanist there is a very different scientific make-up of the flowers, I’m sure, but to the appreciative casual viewer they provide just a breathtaking sight of clusters of upside down crocus-like flowers — I don’t think they really resemble snowdrops — and some varieties have a pinkish flush.
"H. monticola and H. carolina both come from the US and are the two most available species. H. monticola is large in frame, leaf and flower but has a tendency to become rather twiggy and messy. H. carolina is, in my opinion, even messier and is often a large twiggy shrub with a penchant for suckering — but in early May, just before the arrival of its leaves, hold onto your hat.
"They may lack the retina-burning intensity of some of the more vulgar cherries but they stop you in your tracks by their sheer elegance, their dainty nodding flowers and the sheer number of them — simply awesome.
"Later in the year, rather unusual winged fruits appear, looking like tiny chocolate oranges with some of the segments eaten, however evenly, which does bring interest into the autumn/winter months as the foliage is certainly seasonally unremarkable. I would never plant the Halesia as a main player, centre stage in the garden, but as reliable co-stars they are invaluable."
Species and varieties
H. carolina is a lovely, deciduous small tree that produces pendent clusters of white, bell-shaped flowers with a golden centre and delicate fragrance in the spring, at the same time as the fresh green foliage that has downy pale-green undersides. The flowers are followed by persistent winged fruits that will often stay on the tree into winter. In autumn the leaves turn golden yellow. Height: 8-15m. Spread: 10m.
H. carolina Vestita Group AGM (H5) is a fast-growing, medium-sized deciduous tree that produces hanging, bell-shaped white flowers, sometimes tinged pink, in the spring, followed by four-winged pale-green fruits. Its oval leaves turn yellow in the autumn. Height: 12m. Spread: 8m.
H. carolina (Vestita Group) ‘Rosea’ is a rare selection that produces masses of hanging, pale-pink flowers in late spring, standing out against the dark-green leaves. Height: 8m. Spread: 6m.
H. carolina Monticola Group has larger leaves and flowers than the straight species. It is a vigorous shrub or small tree with pure-white bell-shaped flowers before or with the oval, downy leaves. Height: 12m. Spread: 8m.
H. carolina (Monticola Group) ‘Variegata’ is a large shrub or small tree that features leaves with an attractive cream/gold margin. When established, it produces masses of pretty white flowers in early summer. Tends to have a multi-stemmed habit. Height: 5m. Spread: 4m.
H. diptera is a large shrub or small tree. It has a more shrubby habit than H. carolina and is less floriferous. Its stand-out features are its broader leaves and two-winged fruits. Height: 6m. Spread: 10m.
H. diptera Magniflora Group is a rarely seen small tree that produces slightly larger white flowers than those of other snowdrop trees. They cascade down the branches in late spring or early summer. Height: 8m. Spread: 6m.
H. macgregorii is a very rarely available species that hails from China. Produces pendulous, slender white flowers in late spring or early summer. Leaves are mid-green in colour. Height: 4-6m. Spread: 4m.
Thank you to Floramedia, which supplied the main image for this article from its photo library