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In this section a brief account is given of the principal cultivars of lilac, which, as in so many other shrubby genera, have largely displaced the original wild forms in gardens. They fall into two groups. The first and by far the largest and most important, comprises the garden-bred sorts of S. vulgaris, to which have been added in this century various hybrids between it and the closely related S. oblata. The second group is made up of hybrids between members of the series Villosae. The two groups are as distinct horticulturally as they are botanically, and no viable hybrid between them has been raised.
The International Registration Authority for cultivars of the genus Syringa is The Royal Botanic Gardens, Hamilton, Ontario, Canada. A tentative International Register of Cultivar Names in the Genus Syringa, compiled by Dr Owen M. Rogers, was published in 1976 by the Agricultural Experiment Station of the University of New Hampshire, Durham, New Hampshire, USA. To this we are indebted for details of raiser and date of introduction, when not given in Susan McKelvey’s The Lilac, in which a detailed account is given of all cultivars raised before the mid-1920s. This work is one of the great classics of horticultural literature, besides being the authoritative monograph on the genus Syringa. For an excellent short account see: F. P. Knight, ‘Lilacs’, Journ. R.H.S., Vol. 84 (1959), pp. 486-99.
The Kew collection of lilacs has been greatly extended in recent years. The most complete collection is to be seen in Withdean Park, Brighton. It was established in the early 1960s by Mr J. R. B. Evison, then in charge of the Department of Parks and Gardens at Brighton, under whose care it is.
I Lilacs of the Vulgaris Group (Series Syringa)
At the beginning of the last century the gardener had few sorts of garden lilac to chose from. Apart from the common blue there was only the white and the purple or Scotch lilac, and a few minor variations of these two, but by the middle of the century new varieties were coming into commerce in increasing numbers. The first to receive a cultivar-name of modern form was ‘Charles X’ (1831-2), but the use of names of this kind, usually the sign that a horticultural group has come of age, did not become general until the 1870s. Few of the old lilacs have remained in commerce, but most were acquired by the Arnold Arboretum in the 1870s and 1880s when they were still comparatively new, and still grow there, in a collection that must be the largest in the world – about 400 different varieties. Most of the sorts still available have been raised since the 1880s and a remarkably high proportion were the creation of the great firm Lemoine, of Nancy, which with its countless philadelphus, deutzias, weigelas and lilacs has done so much to beautify the gardens of the temperate world. The first double lilacs were raised by Victor Lemoine in the 1870s, from crosses between single-flowered varieties and a double, almost sterile mutant called S. vulgaris azurea plena. The history of this cross, as told by Victor Lemoine to the American lilac enthusiast T. A. Havemeyer, is quoted in McKelvey, The Lilac, p. 264.
Some lilacs raised this century are the result of crossing S. vulgaris with the closely related S. oblata; see S. × hyacinthiflora, p. 531. It would be inconvenient and indeed pointless to list these hybrids separately, and they are identified below by placing Hyacinthiflora in brackets after the name. The distinctive character of these hybrids lies not in the flowers themselves as in the fact that they are borne earlier than in the varieties deriving from S. vulgaris purely – in the first half of May or even in late April – and thus help to lengthen the season. They show hybrid vigour and tend to grow rather tall and lanky, a character that makes them suitable more for growing at the back of a mixed planting than as specimens. There must, incidentally, be a suspicion that some of Lemoine’s later productions have S. oblata in their parentage even though they are classified as cultivars of S. vulgaris. ‘Maréchal Foch’ is an example.
Cultivation and Pruning. – The lilacs of this group need full sun or the lightest shade, and thrive best in areas where the summers are warmer than the average. To be obtained at their best they must be given generous treatment. Any soil is suitable except a very acid one, and a deep, stiff but well-drained loam is best of all. A chalky soil is very much to their liking, provided it is deeply dug and well fertilised. A mulch of compost or well-rotted manure helps them, and so too does a dressing of bone meal. They need a minimum spacing of 10 ft, and 15 ft is not too much. An important item in the cultivation of the finer lilacs is the removal of the flower-trusses as soon as they fade, so as to prevent the formation of seed, thereby concentrating the energies of the plant in the new growth and the succeeding crop of flower. This dead-heading may not be practicable once a plant has reached its full height, but should always be done when the plant is young. The lilacs need no systematic pruning, but in order to obtain fine trusses the weaker and superfluous shoots may be cut out at the same time as the old inflorescences are removed. But some modern sorts, especially those of the Hyacinthiflora group, are of vigorous and rather lax habit. These should have their branches shortened by about one-third after flowering, to stop them becoming too lanky. Isolated bushes – and a fine, shapely lilac is an admirable ornament for a lawn – should be trained to a single stem by removing all the lower buds and subsequently the lower branches. However, in North America, where borers are an insect pest, they are better grown on several stems, each arising from ground-level – the vigour and size of the plant being maintained by cutting out the oldest shoots in sequence. As the lilacs of this group form no terminal bud, and naturally fork their branches every year, some pruning and training is at first needed to get a tree-like example.
Young lilacs should be treated with patience, as some years may pass before they produce trusses of the characteristic size, shape and colour. The flower-buds of newly planted lilacs should always be removed. Old plants that have grown out of shape or lost vigour respond very well to hard cutting, which should always be done in winter or early spring.
Propagation. – Most lilacs of this group can be propagated by means of half-ripe cuttings, or by soft-cuttings in a mist unit, but the young plants develop slowly. It is of more interest for the private gardener to know whether the plants he buys are on their own roots or grafted. Propagation by layering has long been practised by British growers and is gaining favour on the continent and in the United States. The advantage of having the plant on its own roots is obvious, but its price is inevitably higher than one that is grafted or budded. Plants on common lilac stock grow well and are said to give better blooms than ‘own-root’ plants, but the disadvantage is that, unless a watch is kept, the variety in time becomes overwhelmed by suckers; if it is not known in advance that the plant is grafted then the case is worse. With privet as the stock the scion does not grow so well nor last so long, if it has to rely for the privet’s roots for its sustenance, but plants produced by modern methods are supposed to be planted with the graft union well below the surface of the soil, the purpose of the privet’s roots being simply to sustain the plant until the scion has struck its own roots.
The following selection comprises most of the common lilacs available in Britain, and all those that have received awards from the Royal Horticultural Society. The colours of the lilacs are notoriously difficult to describe, partly because they are impure, and none the worse for that, and partly because they change so much in hue and tone as the flower ages. Susan McKelvey, in her splendid treatment of this group, often devotes five lines to describing the colour of a single cultivar, using the Ridgway colour chart. But she admitted that these detailed specifications were intended only for verification, and stressed that tone, i.e., the degree of saturation, is more important than hue. In the following summary account, the cultivars, apart from the whites, are arranged in two colour-groups – those whose flowers are in the paler shades of near-blue, lavender and pinkish mauve, and those in which the colour is more saturated. The lilacs in the first group assort together amicably. The dark lilacs need more careful placing.
single white flowers
‘Jan van Tol’. Van Tol, Boskoop, c. 1916. – Flowers snow-white, about 11⁄4 in. wide, in long, drooping panicles. Corolla-segments narrow, widely spaced. The result of a cross between ‘Marie Legraye’ and ‘Mme Lemoine’.
‘Mme Felix’. Felix and Dykhuis, 1924. – Flowers in shapely, erect panicles. Raised from ‘Marie Legraye’. A good lilac for forcing.
‘Marie Legraye’. Mme Legraye (?), before 1879. – This old variety was once much used for forcing, and is the parent of many other whites. Flowers ivory-white from yellowish buds. Anthers conspicuous (considered to be a defect in a forcing lilac). Panicles rather narrow and lax.
‘Maud Notcutt’. Notcutt, 1956. – Flowers flat, with broad segments, about 1 in. wide, well displayed in shapely trusses about 1 ft high, carried well above the foliage. Habit fairly upright. According to the raisers the cut sprays last well in water. A.M. 1957.
‘Mont Blanc’. Lemoine, 1915. – Flowers from greenish buds, very large, in unusually tall and broad conical trusses.
‘Primrose’. G. Maarse, Aalsmeer, Holland, 1915. – A sport from ‘Marie Legraye’, with primrose-yellow flowers. A weak grower. A.M. 1950.
‘Vestale’. Lemoine, 1910. – A fine, vigorous lilac, bearing its flowers in long, well-filled rigidly erect trusses. A.M. 1931.
double white flowers
‘Edith Cavell’. Lemoine, 1916. – Flowers large, from cream-coloured buds. Panicles large and rather lax.
‘Mme Lemoine’. Lemoine, 1890. – Flowers large, more or less hose-in-hose, in erect, compact trusses. Very free-flowering, even when young. A seedling of ‘Marie Legraye’, crossed with a double lilac. F.C.C. 1897; A.G.M. 1937.
‘Miss Ellen Willmott’. Lemoine, 1903. – Flowers opening from greenish buds, pure white, hose-in-hose, with broad lobes. Trusses long, open, pyramidal. A.M. 1917. It is usually listed in catalogues as ‘Ellen Willmott’.
‘Monique Lemoine’. Lemoine, 1939. – Flowers hose-in-hose, in broad trusses. A.M. 1958.
‘Souvenir d’Alice Harding’. Lemoine, 1938. – Flowers warm white, hose-in-hose, in tall trusses. Useful for its late flowering, at the end of May or in early June.
single pale flowers
‘Ambassadeur’. Lemoine, 1930. – Flowers pale near-blue from pink buds, flattish, well-shaped, with a white eye. Trusses broad.
‘Blue Hyacinth’ (Hyacinthiflora). Clarke, 1942. – Flowers hyacinth-shaped, with long, slender tubes, well spaced, pale blue from mauve buds.
‘Buffon’ (Hyacinthiflora). Lemoine, 1921. – Flowers mauve-pink, about 1 in. wide, with cupped lobes, borne in dense, broad trusses. Lax habit.
‘Capitaine Baltet’. Lemoine, 1919. – Flowers large, violet-purple, fading to a bluer tone. Trusses large, not dense.
‘Clarke’s Giant’ (Hyacinthiflora). Clarke, 1948. – Flowers mauvish pink on the inside, pale lavender outside, about 1 in. wide, in very large, loose trusses. Erect, vigorous habit. A.M. 1958.
‘Diplomate’. Lemoine, 1930. – Put into commerce at the same time as the similar ‘Ambassadeur’, this seems to be uncommon in the trade. The small flowers are slaty blue from deep rosy pink buds, freely borne in open trusses.
‘Esther Staley’ (Hyacinthiflora). Clarke, 1948. – Flowers vivid carmine-red in the bud, opening a pleasant shade of bright pink. Vigorous, erect habit. A.M. April 25, 1961. A.G.M. 1969.
‘Firmament’. Lemoine, 1932. – Flowers near-blue, from pink buds, medium-sized. A charming lilac, in the same style as ‘Ambassadeur’ and ‘Diplomate’.
‘Lamartine’ (Hyacinthiflora). Lemoine, 1911. – Flowers about 1 in. across, pinkish mauve, opening towards the end of April. A tall erect bush. This was one of a batch of hybrids between S. oblata var. giraldii and various cultivars of S. vulgaris raised by Emile Lemoine and put into commerce in 1911 (his father Victor Lemoine died in that year at the age of almost ninety). ‘Lamartine’ was planted at Kew in 1912, and received an Award of Merit when shown from there on April 26, 1927. According to the raiser himself, these hybrids did not prove popular with gardeners. Perhaps their lanky habit and early flowering told against them.
‘Lucie Baltet’. Baltet, before 1888. – Flowers flesh-pink in open trusses. A charming lilac, now uncommon but represented in the Kew collection. Mrs McKelvey considered it to be ‘one of the loveliest of the single lilacs’.
‘Mme Charles Souchet’. Lemoine, 1949. – Flowers large, in broad trusses, near-blue, borne very freely. Possibly a derivative of the Hyacinthiflora group, as it flowers in early May.
‘Maréchal Foch’. Lemoine, 1924. – Carmine-pink buds, opening pinkish mauve and ageing to lilac pink. Large, well-formed trusses. Its tall and narrow habit, as well as its early flowering suggests some Hyacinthiflora influence in its makeup, though, like the preceding, it is classified as a pure S. vulgaris.
double pale flowers
‘Alphonse Lavallée’. Lemoine, 1885. – Large flowers, lavender blue shaded with pink, from purple buds. One of Victor Lemoine’s first double lilacs, now uncommon.
‘Belle de Nancy’. Lemoine, 1891. – Flowers deep purplish pink in the bud, opening lilac-pink and fading to bluish mauve, in rather long, narrow clusters.
‘Capitaine Perrault’. Lemoine, 1925. – Flowers large, in wide trusses, rosy mauve. Useful for prolonging the season as it is one of the last to flower.
‘Edouard André’. Lemoine, 1900. – Carmine pink in the bud, opening rosy pink, in broad, open trusses.
‘Edward J. Gardner’. Gardner, Wisconsin, USA. – Flowers semi-double, light pink, in long trusses; buds rich purple. A fine new variety, introduced to this country by Messrs Notcutt.
‘General Pershing’. Lemoine, 1924. – Flowers of variegated appearance, lilac-pink mixed with paler pink and light violet.
‘Katherine Havemeyer’. Lemoine, 1922. – Flowers large, at first lavender-purple, fading to a pinker tone. Trusses dense, broadly pyramidal. One of the finest and most widely grown of lilacs. A.M. 1933. A.G.M. 1969.
‘Mme Antoine Buchner’. Lemoine, 1909. – Flowers hose-in-hose, deep vinaceous purple in the bud, opening soft carmine-rose tinged with mauve. Trusses long and open. A lovely, softly multi-coloured lilac. A.G.M. 1969.
‘Michel Buchner’. Lemoine, 1885. – Flowers pale rosy lilac, in tall trusses.
‘Olivier de Serres’. Lemoine, 1909. – Flowers light violet shading to a pinker tone, in large trusses. Strong growing, but not flowering freely when young.
‘President Grévy’. Lemoine, 1886. – Flowers deep pink in the bud, opening lavender blue with a paler margin. Clusters large and pyramidal. A.M. 1892.
single dark flowers
‘Andenken an Ludwig Späth’ (‘Souvenir de Louis Spaeth’). Späth, Berlin, 1883. – Flowers deep wine-red, holding their colour well, borne in slender trusses about 1 ft long. Vigorous, spreading habit. Although nearing its centenary, this lilac has maintained itself against all rivals, and remains one of the most popular of all. A.G.M. 1930.
The use in Britain of the French name for this lilac is inappropriate, as was pointed out by the Royal Horticultural Society in 1930. It was suggested that the name might be anglicised to ‘Souvenir of L. Spaeth’ (Journ. R.H.S., Vol. 55, p. 279).
‘Charles X’. – This cultivar, put into commerce in the 1830s, probably derived from the old purple lilac, and was raised in France. What is believed to be the true clone is still offered by nurserymen; it has magenta-purple flowers in conical trusses.
‘Congo’. Lemoine, 1896. – Flowers deep purplish red in the bud, paling somewhat when open to a rich lilac-purple, in large, open clusters. Compact habit.
‘Etna’. Lemoine, 1927. – Buds dark claret-red, opening rich purplish red. Late.
‘Mme F. Morel’. Morel, 1892. – Flowers reddish purple in the bud, opening light violet-purple, in very large clusters.
‘Massena’. – Flowers with very concave lobes, deep reddish purple. Spreading habit. A.G.M. 1930.
‘Réaumur’. Lemoine, 1904. – Flowers deep reddish purple, shaded with violet. Late flowering. Vigorous, bushy habit.
‘Sensation’. De Maarse, Boskoop, 1938. – A remarkable lilac, quite unlike any other. The flowers a rich vinous red, edged with white, in tall trusses. A plant at Kew produces a branch-sport with white flowers.
double dark flowers
‘Charles Joly’. Lemoine, 1896. – Flowers dark reddish purple paling to a whitened plum-purple, the recurved segments showing the paler undersides. Erect habit.
‘Condorcet’. Lemoine, 1888. – Flowers purplish red in bud, opening violet purple, in dense trusses.
‘Maréchal Lannes’. Lemoine, 1910. – Flowers large, more or less double, in broad-based clusters, violet with an infusion of pink.
‘Mrs Edward Harding’. Lemoine, 1922. – Flowers semi-double, purplish red, rather quickly fading to pink. Usually considered to be the best double red. Tall growing. A.G.M. 1969.
‘Paul Thirion’. Lemoine, 1915. – Flowers likened by Mrs McKelvey to large double violets in form, carmine in bud, opening rosy red, fading to lilac pink, in dense, broad trusses. Late flowering (after ‘Mrs Edward Harding’). A.G.M. 1969.
II Hybrids of the Villosae Section
The first crosses between members of the section Villosae were made in France late in the 19th century, and a few later by Lemoine (see under S. josikaea), but none of those that were put into commerce attained much popularity and only ‘Floréal’ is mentioned below. Those best known in Britain were raised in Canada and belong for the most part to the Prestoniae group (see S. × prestoniae) or to the similar Josiflexa group (S. × josiflexa, see under S. josikaea). The Prestoniae group is the larger by far of the two, with about 100 named cultivars, but the amount of variation in this group does not justify such a multiplication of names. Although the parentage of most is known, some of the later cultivars were raised from open-pollinated plants, and could therefore have more than two species in their parentage. The flowers of these lilacs, with the long, slender tube and narrow limb characteristic of the section, render the group as a whole very distinct from those deriving from the common lilac. This, and their privet-like scent, may account for the fact that they have not yet won general popularity. They are of easy cultivation in any good soil and attain mostly a height of 10 or 12 ft and as much in width. Unless otherwise stated they flower in June. They are easily propagated by cuttings.
‘Audrey’ (Prestoniae). Preston, 1927. – Trusses conical, dense, about 9 in. long and wide. Flowers light magenta pink outside, almost white within. A.M. 1939.
‘Bellicent’ (Josiflexa). Preston, before 1948. – Flowers clear pink (pale Rose Bengal), fragrant, in trusses about 9 in. long. The most admired of the Ottawa hybrids, with flowers of an unusually clean shade of pink. Journ. R.H.S., Vol. 84 (1959), fig. 163. It flowers towards the end of May. F.C.C. 1946; A.G.M. 1969.
‘Elinor’ (Prestoniae). Preston, 1928. – Flowers in dense panicles about 7 in. long, Magenta Rose in the bud, opening pale lilac-pink outside, pale violet inside. A.M. 1951; A.G.M. 1969.
‘Ethel M. Webster’ (?Prestoniae). Preston, before 1948. – Flowers flesh pink, in lax panicles.
‘Floréal’ (Nanceana). Lemoine, 1925. – Flowers in rather dense trusses about 10 in. long, light lavender-purple. A spreading shrub, flowering freely in May. Lemoine distributed it originally as ‘S. henryi Floréal’. Mrs McKelvey pointed out to him that as a hybrid between S. × henryi and S. sweginzowii it could not be regarded as a variety of the former, to which he replied: ‘Les catalogues d’horticulteurs n’ont pas la prétention d’etre des documents botaniques, et je ne désire pas changer ce nom.’ (McKelvey, The Lilac, p. 108).
‘Fountain’ (?Swegiflexa). Preston, before 1948. – This is believed to be a cross between S. reflexa and the original clone of S. × swegiflexa, sent out by Messrs Hesse in 1935. If so, it is a back-cross and certainly seems to be near to S. reflexa. It makes a large bush, with drooping panicles of pink flowers in May.
‘Guinevere’ (Josiflexa). Preston, before 1938. – Trusses about 9 in. long and wide, conical, drooping at the tip. Flowers purple in the bud, opening lilac-purple and fading to a pinker tone. This is the type of S. × josiflexa.
‘Hiawatha’ (Prestoniae). Skinner, 1934. – Flowers in rather short, broad trusses, deep reddish purple in the bud, paler on opening. Low, spreading habit. It is earlier flowering than the Prestoniae hybrids raised by Miss Preston herself. It is recorded that in selecting seedlings Miss Preston chose those in lighter shades, while Mr Skinner favoured the darker-coloured sorts.
‘Isabella’ (Prestoniae). Preston, 1927. – Flowers pale lilac-purple outside, almost white within, in trusses about 1 ft long, dense. This is the type-clone of S. × prestoniae, described by Mrs McKelvey in her monograph and named by her in honour of Miss Preston. A.M. 1941.
‘Kim’ (parentage uncertain). Preston, before 1948. – Flowers mallow-purple, in broad panicles about 10 in. long. A.M. 1958.