Fall Blooming Lilacs - What's going on?

Stressed Lilacs may re-bloom in fall. 

Lilacs in Minnesota typically bloom in the spring and are noted for the fragant purple / pink flowers. Some of us are noticing that the Lilacs are blooming again in late summer due to stress from unusual weather conditions.

Healthy lilacs in bloom

Unhealthy Lilac shrub blooming in October.

Julie Weisenhorn, a professor and horticulture educator at the University of Minnesota Extension, explains that this second bloom is a survival strategy for future generations and does not harm the plants. This re-blooming, observed during an unusually warm September and October, is not normal and indicates stress from past extreme weather, including dry summers and a unusual winter weather.

While Minnesota is not currently in a drought, the wet period can also contribute to this phenomenon. Plants sometimes take time to react to stressors like blights, pests, and weather fluctuations, leading to behaviors such as lilacs blooming again in the fall.

Care for the Lilacs in the spring and fall.

Take care of your lilacs to keep them blooming in spring. You may want to treat your blighted bacteria or mildew fungus infected lilacs with in the spring to keep them healthy. There are chemical sprays available to treat lilac bacterial blight and other general anti-fungal sprays. Most chemicals require full coverages spray in the spring of interval of 7-10 days, especially after each rain.

In the fall, it is best to take action for the prevention of continued infection can be mitigated by removing leaves and matter below the lilacs and burning or burying the matter. It is not advisable to compost the potentially fungus infected leaves, as the compost temperature will not kill the fungus.

Check at your local nursery or hardware store for the sprays for your Lilac trees.

Sources: https://restorelilacway.com/lilacs-reblooming-confused-by-fall-weather/