Maybe nothing! Don’t be alarmed if the leaves of your evergreen rhododendron are drooping and curling downward this winter. It may look concerning but, the drooping and curling is the species response to cold temperatures. This response, known as thermonasty, helps protect the plant from freezing temperatures. A recent visit to the Missouri Botanical Garden reminded me of this occurrence. The garden has several rhododendron varieties and while it was not bitterly cold, the leaves were responding to the temperature. Some diseases show the same symptoms. If the curling continues when the weather has warmed contact the extension office for help.
Rhododendrons are a common evergreen or deciduous flowering shrub. They are available in various shapes, sizes and colors. They can attract numerous pests and be susceptible to many diseases. Despite this, they remain popular spring-flowering options for gardeners and can be a healthy beautiful mainstay in the garden.
Providing rhododendrons with the environment they prefer goes a long way in having a healthy plant. They thrive in well-drained, organic-rich, moist, acidic soil. There are shade and sun tolerant varieties but no rhododendron does well in a southwest sun exposure- that is too much sun for these plants.
Despite the cold temperatures, the visit to the Botanical garden was great. There are beautiful plants to see, even on a cold overcast day in February. The garden has a number of different witch hazel species on the grounds. The native vernal witch hazel, (H. Vernalis) and H. mollis, the Chinese witch hazel were a delight to see in full bloom. The native species had a wonderful fragrance. If you are looking for a native shrub this spring, this is one to consider. Along the pathways, national and state champion tress are a marvel to see. I can’t help but wonder at the changes and challenges these majestic trees have endured Indoors at the garden, the annual orchid show was taking place. The yearly event displays the gardens orchid collection. The first orchids were a gift in the 1870s! The collection has grown over the years to include hybrid development and orchids increased from collection and gifts.
There are 6.500 plants in the collection and the annual show displays the best of the best. Even in winter, the botanical garden has something for everyone. If you have not visited and find yourself in St. Louis, it is quite an experience no matter what time of year.
Kathi Mecham is a MU field specialist in horticulture.