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|Summer Flowering Magnolia|
Question. Here it is, July 5, 2001, and this silly Magnolia tree has a number of flowers in full bloom. Why is this tree blooming out of "normal" sequence?
Answer: Spring-blooming woody plants initiate flower buds on previous year's wood, then rely on chilling to stimulate maturation of the flower buds. In other words, the flower buds require a certain amount of chilling before they break out of dormancy.
Different species and even cultivars within a species vary in their requirement for chilling units. In general, plants that flower earlier in spring require fewer chilling units than plants that bloom later. Plants such as magnolia and some rhododendron commonly rebloom sporadically in the summer and into the fall. Though the total amount of bloom for the following spring might be reduced, this out of sequence blooming is not harmful, and usually there are still plenty of buds left to provide a spring show.
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Last updated: 7 July 2001/tlm.
The Plant & Pest Diagnostic Laboratory at Purdue University.