Reblooming plants reflect the growing season
UNIVERSITY OF MINNESOTA EXTENSION - www.extension.umn.edu
Lilacs blooming out of season are referred to as being "remontant." Photo: Allan Paul Eilen
Lilacs usually bloom in spring, but many people are seeing them bloom again now. Why?
Like so much in Minnesota, the weather has a lot to do with this phenomenon.
Environmental stress such as heat and drought may cause plants to respond in a variety of ways. For example, plants may flower and produce a great deal of seed, called “masting," due to stressful environmental conditions. Plants that rebloom are termed “remontant” when they flower a second time in one growing season.
Neil Anderson, in the UMN Department of Horticultural Science, filled me in on how plants become remontant. Spring-blooming plants produce or “set” their buds soon after blooming. If bud set is followed by environmental stressors such as heat or drought and then a cold period simulating winter, flower buds may break dormancy and open.
This can occur with many different perennial plants in the landscape when a plant’s minimum number of cold (chilling) hours has been met. Plant hormones that promote dormancy and prevent the buds from opening are broken down during the cold period, releasing the flower buds to open. And, voila! Lilacs in autumn.
The good news is that late blooming won’t significantly affect next year’s spring bloom, since it usually only affects a few, but not all, of the flower buds developed for next year.
It’s a good idea to note these observations in your gardening journal and record how the plants perform next spring. In the meantime, enjoy lilacs in autumn!
