American Nurseryman Magazine - Horticulture Magazine and Horticulture Books - Syringa oblata - February, 2014 - DEPARTMENTS

American Nurseryman Magazine - Horticulture Magazine and Horticulture Books - February, 2014

DEPARTMENTS

Field Notes: Syringa oblata



Photos courtesy of Missouri Botanical Garden/Plant Finder: Glenn Kopp

One of the most romantic things about plants is that every flower has a meaning, and for me the globally unique fragrance of zi? di¯ng xia¯ng, early lilac, means home. Syringa oblata is the City Flower of Hohhot, Inner Mongolia. The special fragrance makes early lilac a popular landscape plant in northern China. Every April and May, crowds of people visit Hohhot to picnic among the Syringa oblata. The City of Hohhot's Horticulture Department has planted countless seedlings of early lilac along the roadsides and throughout an entire park as a welcome to the annual visitors.

Name

Syringa oblata

Common Name

Early lilac; broadleaf lilac; zi? di¯ng xia¯ng

Hardiness

3 to 7 (4 to 6 best)

Mature height

8 to 12 feet

Mature spread

8 to 12 feet

Classification

Spreading multi-stem shrub or small tree

Landscape use

Specimen, screen or informal hedge; mixes well with other tall shrubs

Ornamental characteristics

Showy fragrant flowers; good cut flower; purple-red fall color; urban-tolerant with good soil drainage

Early lilac blooms one to two weeks earlier (thus the common name) than its more well-known and common lilac cousin, Syringa vulgaris, blooming for seven to 14 days sooner than common lilac in late April through May, depending upon the weather pattern. Flower color is typically pale purple, but white forms are common (variety alba). Half-inch-long florets develop on 2- to 5-inch-long panicles, followed by brown, dehiscent seed capsules that will persist if not removed. Flower buds develop in fall on the tips of growing stems (old wood), so do not prune plants in summer or fall to avoid removing flowering shoot tips. Removal of the spent panicles before seed set tends to improve flowering the following spring. Any necessary pruning for shaping or size control is best done at this same time.

Syringa oblata (Family Oleaceae), also commonly called broadleaf lilac, is a deciduous, spreading, multi-trunked shrub with arching branches up to 8 to 12 feet tall and wide. Native to northern China, early lilac has opposite, simple leaves with a variety of shapes from ovate-orbicular to reniform, wider than long, 2 to 4 inches wide by 2 to 3 inches in length. Foliage has acute to long acuminate tips, subcordate to truncate to broadly cuneate leaf bases, entire leaf margins with glabrous or slightly pubescent, dark green to bluish-green foliage that initially emerges bronzy-colored. Leaf petioles are ¾ to 1¼ inches long. Foliage develops a purple-red tint in fall, a characteristic unique among lilacs.

Most of the early lilacs growing in the United States appear to be Syringa oblata subsp. dilatata, often called Korean early lilac. This variety has narrower but longer flower panicles and corolla tubes, and narrower but longer leaves, on shorter, shrubbier plants. Such varieties are typically less cold hardy than those of northern China. There are many named varieties of hybrids between Syringa oblata and Syringa vulgaris (Syringa × hyacinthiflora) that are commonly called early flowering lilacs.

Early lilac grows naturally in full sun on the hillsides of thick forests near streams, and at altitudes of 1,000 to 8,000 feet. Although tolerant of many urban soil conditions, early lilac prefers organically rich, evenly moist, slightly acidic to slightly basic soils. Once established, very little fertilization is necessary. In less acidic soils, supplemental magnesium and iron improves leaf color and flower size.

Syringa oblata can be propagated from seeds and cuttings, or by grafting. In northern China, seeds are sown in furrows in greenhouses or outside, with spring best for both (although fall sowing is used). When seedlings have four to five leaves, they are thinned and/or transplanted to individual pots or planting areas. If clones are desired, fall or winter branch-tip cuttings root well. In northern China, grafting typically takes place in late June or early July. Veneer or splice grafts are commonly used. Inverted saddle grafts have been used on larger plants.

If bare root or container-grown plants are obtained, soaking the root system in clean, fresh water upon delivery for five to 60 minutes before planting has improved transplant survivability and establishment.

Early lilac is susceptible to the same diseases and pests as common lilacs. Early lilacs can get leaf spots, anthracnose, mildews and wilts caused by fungi and bacteria. Aphids may spread a few viruses among lilacs. Most of these issues arise during the peak heat and humidity of the summer, and are slightly reduced if plants have good air circulation. Root rots are common when plants are growing in poorly drained soils. Compared to Syringa vulgaris in southeast Missouri, Syringa oblata is more heat-, drought- and humidity-tolerant, and suffers from powdery mildew less frequently.

Slugs and leafminers are routine pests that damage foliage in northern China. Aphids, caterpillars, borers and scale are present, but less frequent.

In Missouri, I have seen many species of butterflies and hummingbirds visiting the flowers of early lilac. Deer and rabbits appear to prefer to eat other plants.

Wherever I may live, I hope to always have Syringa oblata present in the landscape. The early lilac fragrance will always provide some hometown comfort.

Li Yini, agribusiness:horticulture student
Sven E. Svenson, horticulture professor
Department of Agriculture, Southeast Missouri State University
Cape Girardeau, Mo.
sesvenson@semo.edu