Ah, fall. That time of year when a respite from oppressive heat and humidity comes to south Mississippi. Fall, to me, is the best time of year. Growing up in Michigan I appreciated the great leaf color show every year. If pressed, I will admit to missing that (but not the awful dreary weather that comes with it). Most of the plant species in south Mississippi are not known for their fall color. Sure, there are some Swamp Red Maples (Acer rubrum) and Sweetgums (Liquidambar styraciflua), but most don’t have really good fall color. One primary reason for that is the lack of cold temperatures. Blueberries do have some fall color, some cultivars and species more so than others. But, let’s talk more about why fall color happens in the first place.
Many blueberry leaves turn red in the fall — or so it seems. Actually the red pigments are there the whole time, it is just that the chlorophyll (green) overshadows the other colors. In the fall, these chlorophyll pigments degrade, leaving behind the red and orange colors. Chlorophyll breaks down in sunlight so the plant needs to continue synthesizing new chlorophyll to keep the green color in its leaves. The conditions that promote this are warmth and sunshine, both at their peak during summer. Part of the chlorophyll degradation is the plant preparing for winter — it is reallocating nutrients back to the root system. Since leaves are mainly disposable on deciduous species, it makes sense for the plant to take nutrients like Nitrogen and return it to a permanent plant structure. Once stored in the roots it can be reused in the next year.
Blueberries have anthocyanins in the leaves. Once the chlorophyll is lost, the leaves appear red due to the color spectrum of light it is absorbing. This is a natural process that helps the plant maintain leaves while it reallocates nutrient reserves to the root system. Of course there are times of the year when we don’t want to see red leaves on blueberries, especially in the spring after a frost/freeze event, but seeing red during the fall is a natural, normal thing that portends the coming winter.
Great red fall color can be seen on commercial blueberry cultivars, but also native Vaccinium species like V. elliottii and V. darrowii. Below is a photo of ‘Springhigh’, a southern highbush blueberry released from the University of Florida blueberry breeding program.
Many blueberry plants are still green here in south Mississippi. Many won’t turn red, or at least not completely, before falling off the bush. Some cultivars retain their leaves throughout the winter. So much variation among blueberry cultivars and species! Enjoy the fall — while it lasts.