RHS Journals
The Garden
April 2008
Hearts and flowers
Outstanding among spring-flowering small trees, Cercis have never received the popularity they deserve but, as Phil Clayton discovers, a wave of recent introductions may change that.
Images: Tim Sandall
Despite the ever-widening range of garden plants, the number of flowering trees for small gardens remains limited. Some spring to mind: ornamental cherries and crab apples of course, rowans, laburnum and the odd magnolia. While there are others, few are readily available – a surprising fact given the decreasing size of new gardens.
One fine example, long-regarded as among the best for early summer, is Cercis siliquastrum (Judas tree). This leguminous native of the eastern Mediterranean has been cultivated in the UK for around 400 years, and can be a dazzling sight. In late April or May, clusters of bright pink or purple (white in f. albida ) pea flowers appear. Cercis exhibit ‘cauliflory’, that is, they are stem-flowering, blooms curiously bursting from joints of as-yet leafless branches – in some cases pushing out from the main stem. While young, Cercis are shrubby, but with age, a trunk or multi-stemmed structure forms; trees seldom top 10m (33ft) (6–8m (20-27ft) is usual). Foliage is heart-shaped and, in a good year, bunches of broad purple pods appear; seed inside germinates well, a reliable method of propagation for the species.
Sadly Cercis has never been popular. This could be to do with its biblical associations (legend tells us this was the tree Judas hanged himself from after the great betrayal) or the fact it likes hot, dry conditions. Historically the best UK examples have been in southeastern England, but today they thrive across much of Britain. There is, however, more to Cercis than the Judas tree. From various other species come an expanding range of exciting garden trees.
Foliage and flowers
Cercis canadensis (redbud), native to North America, is similar to Judas tree, but larger and with leaves of brighter green. The rosy-pink flowers (white in C. canadensis f. alba), while attractive, are slightly smaller.
Redbuds have, however, produced some fine selections. The best known is C. canadendsis ‘Forest Pansy’. One of the first to be named, this is among the finest of trees for foliage effect. Sumptuous purple, heart-shaped leaves provide a wonderful contrast with other plants and it has become a favourite with garden designers, partly because it has a long season of interest. Plants produce quantities of rose-pink flowers in spring and, as these fade, new leaves emerge, waxy and shining in the spring sunshine, expanding each day until the tree is resplendent in its purple gown. The leaves are of good colour throughout summer, until in autumn they create yet more drama, turning reddish, then yellow before falling. If anything ‘Forest Pansy’ is more adaptable than a Judas tree – it will take some shade, especially when young, and does best in shelter and a moist, well-drained soil.
American beauties
‘Forest Pansy’ was developed in the USA, where breeding work has produced more selections, the first of which are now appearing in the UK. These are as yet relatively untested here, and only time will tell how well they perform, but the recent success of ‘Forest Pansy’ promises much. With a graceful, weeping habit is C. canadensis Lavender Twist (‘Covey’), spectacular in flower with cascades of bloom on bare, pendulous, slightly twisted branches, followed by large, heart-shaped leaves. It is a fine specimen plant, unlike any other hardy ornamental tree, and suits small gardens well; trees are grafted and reach no more than 3m (10ft). Similar in size and habit, but of different appearance is C. canadensis ‘Cascading Hearts’. This has leaves half the size of Lavender Twist and is denser and neater – it also produces pink flowers.
Among upright selections there is great variety. Most compact of all, C. canadensis ‘Little Woody’ has appeal, its small, dark green, puckered leaves attractively tinged with red when they emerge. They are neatly arranged up the stems, each directly above the next, as if placed by hand. It reaches around 2–3m (7-10ft). Slightly larger is C. canadensis ‘Ace of Hearts’ , which has the makings of a superlative garden plant. The leaves, small but perfectly heart-shaped, are held up the stems with elegant poise. In flower, however, this plant really performs. Its pale blooms, soft mauve with darker markings, are produced in large quantities, studding the dark stems in late spring.
Other larger C. canadensis selections noted for their flowers are ‘Appalachian Red’ with red blooms, and ‘Flame’, a selection from 1902, but seldom cultivated. It is remarkable for its large double flowers of soft pink, produced freely in mid to late May. The most dramatic for foliage is new ‘Hearts of Gold’ . Its large leaves are golden yellow, brightest when young, although they slowly turn pale green. It seems strong-growing and produces mauve blooms. If variegated foliage appeals, ‘Floating Clouds’ will be of interest. Its leaves are splashed irregularly with white – some have more white than green, others just a few flecks. It has a slightly irregular growth habit and its leaves can be a little distorted in shape. Not yet available in the UK is ‘Bloodspot’ , a vigorous, upright-growing selection with purple-flushed leaves similar to ‘Forest Pansy’.
Cercis canadensis var. texensis (syn. C. reniformis) has a more shrubby habit with rich-green, glossy rounded leaves. From this, too, come promising selections. ‘Oklahoma’ has particular attraction, especially in flower, for the blooms are rich purple, more intense in colour than other selections. They are produced in great profusion, smothering the stems, undoubtedly a dramatic sight on mature plants, which can reach 8m (27ft) in height. The leaves look tougher than on C. canadensis selections with a shiny, wrinkled appearance. A weeping cultivar, C. canadensis var. texensis ‘Traveller’, and white-flowered ‘Texas White’ are also available.
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