“Is my rhody confused?” our customers ask. “They’re flowering now, in the fall. Will they still bloom in the spring?”
To some extent this happens every autumn. The hours of daylight and darkness are the same in the fall as in the spring, and the temperatures are a similar combination of warm days and cool nights. Since we also usually have a few good fall rains after a dry spell in the summer, all of this adds up to these conditions giving the plants the false idea that it’s spring. Sometimes people even trigger this growth response by feeding their shrubs a synthetic, as opposed to an organic, fertilizer sometime in late August or September.
Some years we see more such fall flowering than others. In the fall of 2011, after many plants were shocked by the salt spray of hurricane Irene in August, there were spring flowering trees in bloom as well as many Rhododendrons. No matter what the cause, however, everyone would like to know if their plants will still blossom the following spring. The answer to that is “It depends.” Plants that put out only a few fall flowers should still have a good show of color the following spring. But if a shrub has opened most of its buds in autumn, or has been very shocked by drought, salt burn or other stressful conditions, it may not flower well the next year.
To help with spring flowering no matter what Mother Nature dishes out, water your plants deeply every week or two. Amend the soil from the top down by applying an inch of compost or composted manure periodically. Wash off salt spray promptly after a hurricane, and don’t give your plants a synthetic fertilizer in the fall.