RIVER VALLEY — As surprising as it is that a crabapple tree is blossoming on October 4, it was even more surprising to find out that it’s not that uncommon.

According to Rosie Lerner, a retired consumer horticulture specialist educator for Purdue University, landscape plants blooming out of sequence in the fall happens to some extent in many years. Rhododendrons, crabapples and saucer magnolias are some of the most commonly reported species blooming in the fall.

Here’s how it works, Lerner writes: “Spring-blooming woody plants initiate flower buds on previous year’s wood and rely on chilling to stimulate the buds to mature. In other words, the flower buds require a certain amount of chilling before they break out of dormancy to open their flowers. Cool nights—like we’ve enjoyed recently—can provide enough chilling to cause plants to bloom out of their ‘normal’ sequence. And in some cases, stressful conditions (such as summer drought) can substitute for some of the required chilling.

“Another factor for some plants is that the flower buds they initiate in late summer do not develop the proper plant growth inhibitor hormones that normally keep the buds dormant. In such cases, autumn warm spells can induce these flower buds to open.

“Although blooming out of sequence may reduce the total amount of bloom for the following spring, it is not harmful. Usually, there are still plenty of buds left to provide a spring show.”