The Japanese lilac, scientifically known as Syringa reticulata, is a species of flowering plant in the family Oleaceae (which also contains privet and forsythia). Also referred to as the Japanese tree lilac, it is a deciduous tree or large shrub in nature. It is native to Japan and China where it naturally occurs in forests, woodlands and scrublands in these regions.
The tree produces large panicles of creamy white flowers against the dark green foliage in late spring to early summer. It has a moderate growth rate, an upright growing habit, and a rounded shape. It is commonly grown as an ornamental in Europe and North America. Japanese tree lilac is the only species of lilac that attains a tree-like form and size.
Japanese Tree Lilac can be grown as an understory tree or as a specimen tree. When in full bloom, the shrubs appear beautiful in the landscape. It even attracts butterflies, bees, and other pollinators to the garden.
Botanical Characteristics
- It grows as a small to medium-sized tree, reaching heights of 20 to 30 feet (6 to 9 meters) tall, with a spread of 15 to 25 feet (4.5 to 7.5 meters).
- It has an upright, rounded form with a dense canopy of dark green leaves. The leaves are ovate to elliptic, arranged oppositely along the stems, and turn yellow or pale greenish-brown in the fall before dropping.
- The leaves are 2-4 inches long and 1-3 inches wide, and are present on the tree early in the year, often by late March.
- Flowers are creamy-white and borne in long panicles up to 12 inches long at the ends of the branches. The somewhat fragrant flower clusters bloom in early summer and remain attractive for 1 to 2 weeks.
- After flowering, Japanese lilac produces small, brown capsules that contain winged seeds. Capsules contain 2 winged seeds. The capsules appear in large clusters that remain on the plant through winter. The fruit is a cluster of capsules containing seeds that are scattered by wind.
- Bark and stems are glossy reddish-brown, with numerous lenticels. Bark resembles cherry bark; older trees develop scaly, grayish plates.
- It suited to USDA hardiness zones 3 to 7, although some cultivars may exhibit slightly different tolerances.
- Generally the plant has a lifespan of about 30 years but with proper care it can get to 50 years or more.
- Japanese Tree Lilac is not a great choice for wildlife, however it does have value as a nesting location for many songbirds, according to North Dakota State University.
Different Cultivars of Japanese Lilac Tree
‘Ivory Silk’ (Syringa reticulata ‘Ivory Silk’)
One of the most popular cultivars, ‘Ivory Silk’ usually feature abundant clusters of creamy white flowers and upright, vase-shaped form. It reaches heights of 20 to 25 feet (6 to 7.5 meters) tall and spreads of 15 to 20 feet (4.5 to 6 meters) wide.
‘Golden Eclipse’ (Syringa reticulata ‘Golden Eclipse’)
This cultivar features golden-yellow foliage in spring, gradually transitioning to greenish-yellow as the season progresses.
‘Summer Snow’ (Syringa reticulata ‘Summer Snow’)
‘Summer Snow’ usually feature a profusion of large, white flowers that bloom in early summer. It has a rounded, compact form and reaches heights of 15 to 20 feet (4.5 to 6 meters) tall.
‘Ivory Pillar’ (Syringa reticulata ‘Ivory Pillar’)
This cultivar usually has a narrow, upright form. It produces abundant clusters of fragrant white flowers in late spring to early summer.
‘China Snow’ (Syringa reticulata ‘China Snow’)
‘China Snow’ is similar to ‘Ivory Silk’ but has slightly smaller flowers. It features an upright, rounded form and produces masses of creamy white flowers in early summer.
‘Mt. Fuji’ (Syringa reticulata ‘Mt. Fuji’)
Named after Japan’s iconic mountain, ‘Mt. Fuji’ feature large, showy flower clusters and strong fragrance. It has a rounded, spreading form and reaches heights of 20 to 25 feet (6 to 7.5 meters) tall.
‘Regent’ (Syringa reticulata ‘Regent’)
‘Regent’ has smaller leaves than other varieties. It produces abundant clusters of white flowers in early summer and is known particularly in Japan for its resistance to powdery mildew, a common fungal disease affecting lilacs.
How to grow and care for Japanese lilac (Syringa reticulata)
| Location | Choose a spot with full sun to partial shade and well-drained soil. Ensure adequate space for mature growth. |
| Planting | Dig a hole twice as wide as the root ball, place the tree, backfill with soil, and water thoroughly after planting. |
| Watering | Keep soil consistently moist, especially during the first few years. Water deeply and infrequently. |
| Fertilizing | Apply balanced, slow-release fertilizer every spring and summer time. |
| Pruning | Prune in late winter to early spring, removing dead/damaged branches and thinning the canopy as needed. |
| Mulching | Apply organic mulch around the base to conserve moisture, suppress weeds, and regulate soil temperature. |
| Disease/Pest Control | Monitor for pests/diseases, treat promptly with appropriate methods such as pruning or applying insecticidal soap. |
| Winter Care | Provide protection for young trees in harsh winters, avoid heavy pruning in fall to prevent frost damage. |
Common Diseases That Affect Japanese lilac (Syringa reticulata)
Powdery Mildew
Powdery mildew is a fungal disease that appears as a powdery white coating on the leaves, stems, and buds of plants. It thrives in warm, humid conditions and can weaken the plant over time by inhibiting photosynthesis. To prevent powdery mildew, ensure the trees are properly spaced, avoid overhead watering, and prune out any infected branches.
Bacterial Blight
Bacterial blight, caused by the bacterium Pseudomonas syringae, can cause dark brown or black lesions on leaves, stems, and flowers of Japanese lilacs. Infected tissue may also appear water-soaked or slimy. To manage bacterial blight, prune out infected branches and avoid overhead watering. Copper-based fungicides may help control the spread of the disease.
Verticillium Wilt
Verticillium wilt is a soil-borne fungal disease that can commonly affect Japanese lilacs. It causes wilting, yellowing, and browning of leaves, often starting on one side of the plant. The disease progresses over time, eventually causing branch dieback and plant decline. There is no cure for verticillium wilt. Planting Japanese lilacs in well-drained soil, avoiding stress on the plant, and removing and destroying infected plant material can help prevent the spread of the disease.
Leaf Spot
Leaf spot diseases, caused by various fungi such as Septoria and Cercospora, can cause small to large spots or lesions on the leaves of Japanese lilacs. These spots may be brown, black, or reddish in color and can coalesce to form large patches of dead tissue. Leaf spot diseases are often more prevalent in wet conditions or when plants are stressed. To manage leaf spot, remove and destroy infected leaves and avoid overhead watering.
Pests that commonly affect Japanese lilacs (Syringa reticulata)
Lilac/Ash Borer (Podosesia syringae)
The lilac borer is a type of clearwing moth whose larvae bore into the branches of lilac and related plants, including Japanese lilac. Infestations can lead to branch dieback, wilting, and eventual decline of the affected plant. Look for entry holes in the bark and sawdust-like frass (excrement) near the base of the tree. Pruning out and destroying infested branches can help manage lilac borers.
Lilac Leafminer (Gracillaria syringella)
Lilac leafminer larvae feed on the tissue between the upper and lower surfaces of lilac leaves, creating serpentine mines that may cause leaf distortion and discoloration. While lilac leafminers rarely cause significant damage to the health of Japanese lilacs, severe infestations can lead to unsightly foliage. Pruning out and destroying infested leaves can help manage lilac leafminers.
Aphids
Aphids are small, soft-bodied insects that can congregate on the undersides of leaves and along new growth, sucking sap from the plant and excreting honeydew. Heavy aphid infestations can lead to stunted growth, distorted leaves, and reduced vigor in Japanese lilacs. Insecticidal soap, neem oil, or horticultural oil can be effective in controlling aphids.
Scale Insects
Scale insects are small, immobile pests that feed on the sap of plants by piercing the leaves, stems, or branches with their mouthparts. They often appear as small bumps or scales on the surface of the plant, and heavy infestations can lead to yellowing, wilting, and premature leaf drop in Japanese lilacs. Pruning out infested branches and applying can help manage scale insects.