Photo by Susan R. Crispin, Michigan Natural Feature Inventory


Wild Lilac
By Angie Jackson

Lilacs, known for their sweet and elegant aroma, are one of the most common garden shrubs in the country. Wild lilac (Ceanothus sanguineu) is a threatened species in Michigan that occurs in the Keweenaw Peninsula.

As a nitrogen-fixing shrub, wild lilac supports the growth and health of other plants. It is also an important browse species for animals such as white-tailed deer, mule deer and Rocky Mountain elk.

Physical Appearance:
Wild lilac is a perennial shrub with red or purple stems and white flowers. Its leaves are 4-7 cm long, oval shaped and green. Leaves are alternatively arranged, and sometimes the undersides are hairy. Lilacs will grow up to three meters tall in small bush arrangements, with clusters of flowers growing up to 12 cm long.

Preferred Habitat:
In Michigan, wild lilac prefers volcanic cliffs and volcanic conglomerate ridgetops characterized by scattered, shrubby tree areas, such as the northern Keweenaw Peninsula. In the western United States, wild lilac grows in canopy gaps, in mixed conifer forests and on slopes. It thrives in sunlight and hot, dry climates.

Life Cycle:
Wild lilacs flower in late May and June, and fruit in July. Seeds are covered with a water-resistant coat that only opens with exposure to heat. Fire, logging and other occurrences that expose the seeds to heat lead to rapid germination. Following this process, growth is rapid, but individual wild lilacs have relatively short life spans of 5-10 years.

Like other shrubs in the Ceanothus family, wild lilacs fix nitrogen through a symbiotic process with the bacteria of the genus Frankia. This process enhances the growth of nearby plants, restores soil and aids the repair of unhealthy land. Researchers say some forest ecosystems in the Pacific Northwest may rely on wild lilac as a main source of nitrogen input.

List Status:
Wild lilac populations are secure in British Columbia, Washington, Oregon, California, Idaho and Montana. However, it is a threatened species in Michigan, with only five occurrences in Keweenaw County. Most Michigan occurrences have been near roads, making wild lilac populations in danger of road development and pesticides. Road use and foot traffic have also established the presence of several invasive plants such as Canada bluegrass and spotted knapweed in the shrub’s habitat, potentially inhibiting its survival.

Protection Efforts:
Currently, there is not a state-wide protection program in place for wild lilac. However, research suggests that controlled burns would help manage the plant and its habitat. Because wild lilac seeds require heat to open, fire would aid in spreading seeds and removing canopy-covering plants to provide sunlight.

At MNA, staff conduct routine controlled burns to manage natural areas and promote habitat health and diversity. Burns remove gaps from the forest canopy, allowing for the conservation of rare and endangered species such as wild lilac.

How You Can Help:
Help promote healthy natural communities by joining the MNA burn crew. Controlled burns are led by trained professionals who redo their training each year. During the training process, new MNA burn crew members are taught to handle the equipment, as well as methods for controlling fire like creating fire breaks and backfires. To learn more about prescribed burns, contact MNA Stewardship Coordinator Andrew Bacon by emailing abacon@michigannature.org or calling (517) 655-5655.


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