Visit the Arboretum almost any day from late April through early June and you’ll find a lilac (Syringa) in bloom. With about 400 individual specimens representing more than 160 taxa, and with almost all known Syringa species present, the Arboretum’s lilac collection is one of the most comprehensive around.
Our earliest blooming lilacs [pdf] are Syringa oblata and its subspecies S. oblata subsp. dilatata. The latter is generally more ornamental, and a cultivar of it, ‘Cheyenne’, is noted both for its flowers and its purplish fall foliage color, a rarity in lilacs.
The mid-season blooming common lilac [pdf] (S. vulgaris) is perhaps the best known and loved lilac. Hundreds of cultivars have been selected and named over the years, most of them wonderfully fragrant [pdf]. Flowers may be single or double and come in white, pink, and many shades of purple. Lilac hybridizers crossed S. oblata with S. vulgaris, resulting in hybrids (S. x hyacinthiflora) with large, fragrant flower clusters that bloom slightly before or with common lilacs.
Late lilac (S. villosa) is one of the latest blooming shrub lilacs. Starting in the 1920s, Canadian horticulturist Isabella Preston [pdf] crossed late lilac with S. reflexa and introduced many cultivars of the hybrid (S. x prestoniae), including several with true pink flowers. These and several other late-blooming lilac species have been widely hybridized; their flower clusters are finer textured than those of common lilac and many are fragrant, though not as wonderful as common lilac, to my nose anyway.
The very latest blooming Syringa are the tree lilac species: Japanese tree lilac (S. reticulata subsp. amurensis) and Pekin lilac (S. reticulata subsp. pekinensis). They both bear cream-colored flower clusters that have a strong scent, which can be a bit overwhelming up close.
Stop in and see these and many more lilacs in the coming weeks.
Nancy Rose, editor of Arnoldia