Joy of Lilacs

S. pubescens, subsp. microphylla, from PII.

A fond memory of my childhood in Cincinnati is mom asking me to cut a bouquet from the two giant common lilacs, Syringa vulgaris, in the garden — the house then sweet with fragrance.

You may be familiar with the Olsen House in Cushing, Maine, the subject of Andrew Wyeth's paintings from the late 19th century of a Maine coastal family and farm. It’s adorned with towering lilacs.

Lilacs are truly an heirloom plant in northern gardens, often the only vestige of a homestead. Numerous cultivars exist, but lack heat, drought, disease and insect tolerances for successful culture in the South. ‘Tiny Dancer,’ a 2011 S. vulgaris introduction from Plants Nouveau, is described as heat tolerant, hardy in USDA Hardiness Zones 4-8. It reaches 4-5 feet high and 3-4 feet wide, producing violet-purple buds that open to fragrant lavender flowers in 4- to 5-inch long panicles. I look forward to trialing it in the Dirr garden.

Performance evaluations
Several researchers evaluated lilacs for performance in the southeast. Richard Bir reported excellent performance with S. vulgaris, S. reticulata, subsp. pekinensis, S. meyeri, S. ×prestoniae, S. ×josiflexa, S. pubescens subsp. microphylla, subsp. patula, S. ×chinensis, S. oblata, var. dilatata, and S. ×hyacinthiflora. Work was conducted at North Carolina State's Fletcher Research Station near Asheville, Zone 6b, ~2,000 feet elevation.

John Ruter, professor of horticulture at the University of Georgia, conducted a five-year evaluation (1996-2001) of 18 lilacs in Tifton, Ga., Zone 8a. I visited Tifton many times and it is one of the hottest parts of Georgia. 'Miss Kim' was one of Ruter's favorites, but grew only 2.8 feet by 3.3 feet. Two others were highly rated including S. × laciniata (7.3 feet by 9.7 feet), the most vigorous, and at that time NA 62974, now 'Old Glory' (6 feet by 4.6 feet). 'Declaration' grew 6.6 feet by 5.2 feet and S. meyeri, 3.7 feet by 5.7 feet. All received a rating of Good for flowering. 'Old Glory' was not devastated by late season Cercospora leaf spot.

Hope for the South
So what to do? Certainly the S. oblata complex including var. dilatata offers hope. At the J.C. Raulston Arboretum in Raleigh, N.C., I observed 'Frank Meyer' (white) and var. dilatata performing admirably with flowers in late March. The S. ×hyacinthiflora cultivars require less chill hours and are more heat tolerant. The Decanso hybrids have been underwhelming with 'Angel White,' 'California Rose,' 'Dark Knight' and 'Lavender Lady' tested at PII. In our trial at PII and the University of Georgia, 'Betsy Ross,' 'Declaration' and 'Cheyenne' (var. dilatata type) have maintained reasonably clean foliage into October. 'Cheyenne' has been the best and is now integrated into PII's breeding strategies. 'Declaration' and 'Betsy Ross' are also being utilized with numerous open-pollinated seedlings (November 2012). 'Betsy Ross' has flowered on 3-31-09, typically later than true S. oblata.

S. vulgaris

Hundreds of open-pollinated seedlings of S. oblata yielded several selections with deep purple buds and lavender flowers as well as white. Several yellow-foliage variants also appeared, one with white flowers. It's worth noting that with our long growing season and cultural techniques, most seedlings of S. oblata flower in two years. The compost heap is littered with less-than-stellar S. oblata. Flowers were fully open on 3-18-12 and late spring frosts guarantee degrees of injury.

Josh Kardos, PII breeder, has grown S. pubescens subsp. patula (large leaves) and S. vulgaris seedlings. I noted the subsp. patula developed rich maroon fall color. We plan to assess these for flower qualities in 2013. Might mention that foliage of subsp. patula was free of disease while S. vulgaris was infected. Perhaps subsp. patula, based on reasonable success of 'Miss Kim,' could lead to a clean-foliaged, heat-tolerant lilac reminiscent of S. vulgaris. Josée, the best for foliage in our trials. Greenleaf Nursery recently introduced Sweet Treat (‘GRESWT’), a selection from ‘Miss Kim,’ with increased heat and drought tolerance. It grows 5-6 feet high and 4-6 feet wide and is adaptable in Zones 3 to 8.

More hope
Syringa reticulata and S. reticulata subsp. pekinensis are also in the mix. My observations indicate subsp. pekinensis is better adapted to Zone 7. Plants of S. reticulata at the Milliken Arboretum in Spartanburg, S.C., leafed out and flowered early, appearing tired and tatty by mid to late summer. However, China Snow ('Morton'), a subsp. pekinensis cultivar, has performed magnificently. At the Coker Arboretum at the University of North Carolina and at the Raulston, large specimens of subsp. pekinensis are extant. Seeds of S. reticulata and subsp. pekinensis required a warm and cold stratification to induce germination whereas all other lilacs required only 30 days cold-moist stratification. A lesson for any Syringa breeder is to collect capsules when brown and starting to split, remove seeds and stratify. By November 2012, seedlings of many open-pollinated and controlled crosses from that year have germinated. The seedlings are transplanted to 2½-inch by 2½-inch by 3-inch cells in a seedling mix and grown under lights in a heated greenhouse. These plants are shifted to 3-gallon containers in April-May and grown to flowering. Ideally, seedlings that flower the initial growing season may be remontant or reblooming. This translates to flowering on new growth without the normal flower bud induction under short days and cooler temperatures.

S. meyeri ‘Palibin’

Have I exhausted ALL the possibilities for Southern lilacs? Not so, for a cadre of taxa including S. ×laciniata, S. protolaciniata, S. pubescens, and subsp. julianae, microphylla, and patula, along with S. meyeri and the hybrids Josée, Fairytale Series (particularly Tinkerbelle), ‘Red Pixie,’ Jack Alexander's 'Purple Haze' (sterile) and 'Lilac Sunday' (sterile) will live and/or rebloom in Zone 7. Syringa ×laciniata is the most successful based on 33 years' observations.

I’m always hopeful that a lilac or two will rise above the fray, and more than 50 taxa were tested in containers and in-ground at PII. A limited few have impressed — S. meyeri, S. protolaciniata, Tinkerbell, Josée, 'Red Pixie,' 'Purple Haze,' Lilac Sunday, 'Betsy Ross,' 'Cheyenne' and subsp. pekinensis. S. komarowii was beautiful in flower, but at season's close, the foliage resembled potato chips. Collectively, most of the S. × hyacinthiflora, S. × josiflexa, S. × prestoniae and S. vulgaris significantly underwhelmed. We continue to fine-tune the approach and hopefully will have lilacs for the South (and North) that offer the requisite objectives. In plant breeding, the dictums “Good is the enemy of great” and “We live in the future so might as well plan for it,” are the guiding tenets.

Michael A. Dirr is founder of Plant Introductions Inc.; www.plantintroductions.com.

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