Japanese Tree Lilac

(Oleaceae - Olive Family)

Form

• medium-sized ornamental tree or very large ornamental shrub
• maturing at about 25' tall by 20' wide, although larger under optimum conditions
• upright oval growth habit, becoming more rounded with age
• medium growth rate

Culture

• full sun to partial sun
• best performance occurs in full sun in a moist, well-drained soil of average fertility, but it is highly adaptable to poor soils, compacted soils, various soil pHs, and drought
• propagated by rooted stem cuttings, grafting cultivars onto rootstock, or seeds
• Olive Family, with no diseases and pests of ornamental significance (including resistance to powdery mildew, borers, and scales)
• commonly available, primarily in ball and burlap form, but increasingly in container form

Foliage

• medium to dark green, opposite, ovate, with an acute apex and dull shiny upper surface, and a subtle reticulate branching pattern of the leaf veins near the leaf margin
• fall color is faded green to chartreuse-brown, and ornamentally poor

Flowers

• creamy-white to creamy-yellow, very attractive and fine-textured pyramidal inflorescences, in early June and held well above the fully expanded foliage, as 10" to 12" long pyramidal inflorescences that are pungently fragrant to some, but unpleasantly fragrant or malodorous to most

Fruits

• immature fruits are lime-green, transitioning to chartreuse or light brown in Autumn, noticeable against the darker green foliage but not ornamentally attractive
• Winter-persistent, brown, ellipsoid, dehiscent capsules occur on large fruiting stalks, with the stalk often persisting into the following Spring

Twigs

• light brown and stout on young Winter stems, becoming shiny gray and lenticel-streaked but remaining smooth on young branches, and very much like the branches of Oriental Cherry (Prunus serrulata)
• stems are constantly forking in a dichotomous pattern, usually topped by twin terminal buds at the end of the growing season
• floral buds are slightly larger than vegetative buds

Trunk

• treeform may be either multitrunked, or single-trunked and limbed up, while the shrubform is multitrunked and branching widely at its base
• mature trunks are gray, very Cherry-like, remaining smooth for a long time with horizontal lenticels, then eventually transitioning to bark with plates and fissures

ID Summary

• ovate medium to dark green opposite leaves are mildew-free, while the stems, branches, and young trunks are smooth, brown to gray, heavily lenticeled, and have bark resembling that of Cherry
• the tree or large shrub is primarily known for its cream-colored large inflorescences that are held prominently above the canopy of expanded foliage, being pungently fragrant or malodorous to most, but conveniently flowering above the height of most human noses, and so sparing them in late Spring of the negative scent
• the only Lilac that regularly attains true treeform size and stature

USAGE

Function

• shrubform may be utilized in borders, rows, group plantings, or as deciduous screens
• treeform is found at entranceways, spacious foundations, large raised planters, as a lawn specimen, or as a street tree

Texture

• medium texture in foliage and when bare
• thick density in foliage and when bare (trees have an open to average density when they are young)

Assets

• large, showy, creamy-white inflorescences in early June
• shrubform and treeform selections (with the single-leader treeform being quite stately, especially when in flower)
• virtually disease- and pest-free, with no powdery mildew on the foliage

Liabilities

• inflorescences are considered by most to be unpleasantly fragrant
• poor fall color

Habitat

• zones 3 to 7
• native to Japan

SELECTIONS

Alternates

• trees with showy late Spring or early Summer inflorescences (Koelreuteria paniculata, Liriodendron tulipifera, Magnolia grandiflora, Magnolia virginiana, etc.)
• good ornamental street trees (all must be treeform) (Acer campestre, Amelanchier, Cornus racemosa, Crataegus x lavallei, Koelreuteria paniculata, Malus, Pyrus calleryana [with reservations due to suspect branching], Viburnum lentago, etc.)

Variants

• Syringa reticulata 'Ivory Silk' - usually flowers lightly at 5' tall and profusely at 10' tall, with about the same mature height and width as the straight species, may be grafted onto species rootstock and usually pruned to a single leader, for a stately street tree or specimen growth habit; the cultivar of choice

NOTES

Translation

• Syringa translates as "pipe", referring to the hollow stems.
• reticulata translates as "netlike", probably referring to the subtle branching pattern of the leaf veins.
• formerly known as Syringa amurensis japonica.

Purpose

• Japanese Tree Lilac is an ornamental tree that flowers profusely in early Summer, with large, fine-textured, creamy inflorescences that are held well above the foliage.

Summary

• Syringa reticulata is known primarily as a treeform Lilac with showy, early June, creamy-white inflorescences, without powdery mildew problems on its foliage, and properly used as a specimen, entranceway, or street tree.