Syringa vulgaris L., Lilac

Account Summary

Growth form and preferred habitats

Syringa vulgaris is a deciduous, decorative, garden shrub or small tree 4-7 m in height with opposite, ovate leaves 4-12 cm long. It flowers in April and May, the 'wild' or original introduced form of the plant having mauve or rarely white, terminal, pyramidal, panicles 10-20 cm long.

The plant prefers moist, well-drained, moderately fertile soils of alkaline or neutral reaction. It does well on chalk and limestone, but cannot tolerate very acid, very dry, very wet or very shady conditions. It is not a very aggressive coloniser or competitor, but once it is established, which may require several years' growth, S. vulgaris is long-persistent, its vigorous suckering habit enabling it to form small clones over a period of decades (Clapham et al. 1987; Phillips & Rix 1989).

Introduction and spread

S. vulgaris has been in cultivation in B & I for more than four centuries having been introduced from SE Europe pre-Gerarde's Herball, ie probably sometime just before the publication of the book in 1597 that first describes its cultivation in England. The species is a Balkan native of rocky hillsides from N & C Romania, Yugoslavia, Bulgaria, C Albania and NE Greece (Phillip & Rix 1989). It now seems that many gardeners have over the subsequent centuries developed a love/hate relationship to the plant. The flowers of Lilac cultivars are beautiful and fragrant for a few weeks in early summer, but after this the blossoms die disgracefully, hanging in ugly, brown, persistent panicles and all that otherwise remains for the rest of the growing season is month after month of rather dismal foliage taking up garden space. In late summer, lilacs are frequently attacked by a powdery mildew called Erysiphe syringae, there is no autumn leaf colour display and the seed clusters also fail to present any aesthetic attraction (Clapham et al. 1987; Buczacki 2007).

The heyday of the species greatest popularity was the 19th century and most of the numerous, more than 150, single- and double-flowered cultivars were selected and developed from then, or else from the early years of the 20th century (Griffiths 1994; Sell & Murrell 2007). It became common practice to graft the newly selected cultivars onto the original S. vulgaris rootstock which has the property of suckering freely (Buczacki 2007).

S. vulgaris was first recorded in Britain beyond the garden confines around 1879. It is largely by the power of its vegetative reproduction that the different cultivated forms of Lilac have left gardens and become so familiar a feature of the wider environment into which the species continues to spread at the present time. The increase of S. vulgaris records since the 1962 BSBI Atlas (Perring & Walters 1962), led T.D. Dines to describe the rate of change as, "astonishing", attributing it most probably to better recording of aliens in general, plus a genuine increase of the species presence (Preston et al. 2002).

Flowering reproduction

The many small, bisexual flowers that make up the inflorescence borne in April and May are 15-20 mm in diameter, strongly perfumed, often double. The calyx is yellowish green, divided one-third of the way to the base into four lobes. The corolla varies in colour from pale to dark lilac, blue, purple, pink or white, the tube 8-12 mm, the four lobes 7-8 mm, obovate and rounded at the apex. There are two stamens, adnate to, and enclosed within, the corolla. The style is solitary, green and stays within the corolla tube. The flowers attract insect visitors (mainly bees) that pollinate them and the fruit is a dry, smooth, hard, grey, ovoid capsule, 8-12 mm long that splits into two cells to release four papery-winged, wind-dispersed seeds. Presumably these wind-carried seeds are the primary means of the species' escape from gardens (Ridley 1930; Edlin 1964; Sell & Murrell 2007).

The current author (RSF) has not been able to locate information on some aspects of the basic biology of the plant, such as for instance whether or not it is self-compatible, the level of seed production, seed viability and longevity in soil, germination requirements, and other similar information and statistics.

Fermanagh occurrence

This familiar flowering garden shrub was previously ignored and un-recorded in Fermanagh. It appears rare to occasional in the just eleven tetrads so far recorded, scattered across the east of the VC. The finds are all in roadside hedgerows, where it appears as isolated individuals or as short stretches of suckering shoots. S. vulgaris can occur in situations quite remote from habitation. This suggests to RHN and the current author (RSF) that it most likely originates locally as self-sown garden escapes, rather than as deliberately planted individuals, or dumped garden material. Apart from its initial role in 'jumping the garden wall', seed reproduction appears of less significance in the wild in maintaining the species than the observed active vegetative spread.

British and Irish occurrence

Elsewhere in Ireland, Reynolds (2002) suggests Lilac is deliberately planted in hedgerows. However, usually it is rare, often solitary and forms a patchy distribution in hedgerows, appearing as a relict in old, neglected gardens, on the margins of woods and on waste ground. Generally, it occurs thinly and irregularly distributed near habitation in the lowlands.

Reported instances of plants established in quarries, on cliffs, amongst sand-dunes, by roadsides, shrubberies and thickets in other parts of B & I suggest an origin involving either self-sown seed or discarded garden waste (or both), although it at first might appear unlikely that such a decorative and attractively scented shrub or small tree could be a garden outcast on the scale required to match its present day distribution and frequent occurrence.

Another frequently mentioned habitat is alongside railway lines, where the winged seed from gardens backed onto the railway provided a source of propagules that, being caught in the slipstream of traffic, are swept along to colonise fresh sites, sometimes remote from habitation. In some situations, eg in W Berks, it has become locally abundant by the railway a good distance from any houses (Crawley 2005). In some areas of England, as in Ireland, it probably remains under-recorded, possibly due to lingering recorder prejudice against non-native species (Halliday 1997; Greenwood 2012).

Locally under-recorded in Fermanagh

The presence of this unmistakable and familiar garden shrub was only realised relatively late on in the Fermanagh Flora survey, so it is very probably more frequent in non-garden habitats than has been so far recorded. In adjacent Co Tyrone (H36), for example, S. vulgaris has been recorded from no less than 60 5-km squares, strikingly more than in Fermanagh, and clearly the result of a greater awareness of garden escapes in that VC (McNeill 2010).

The New Atlas editors have commented on the much wider occurrence of S. vulgaris throughout B & I when compared with the 1962 BSBI Atlas. This suggests that Lilac might be actively spreading in more recent years.

The details of the ten other Fermanagh hedgerow records are: Druminiskill, 3 km SE of Derrylin, 27 May 1995, RHN & HJN; Carrignabrook, 2 km E of Glen Bridge, 3 August 1995, RHN & RSF; Knocks Td, 1 km NE of Magheraveely, 4 August 1995, RHN & RSF; Knocks Td, ENE of Lisnaskea, 7 August 1995, RHN & RSF; Drummaw, 1.5 km WSW of Magheraveely, 2 May 1997, RHN; Eshnadeelada Td, 7 km NNE of Lisnaskea, 15 July 1997, RHN; Tullynageeran Td, 1987-99, I. & D. McNeill; near Killyreagh House, Tamlaght, 17 May 2005, RHN; Cloncoohy, 3 km SSW of Teemore, 11 September 2010, RHN & HJN; and E of Summerhill Lough, 15 September 2010, RHN & HJN.

Threats

None.

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