If you have nasal and/or eye allergy symptoms, or your asthma is flaring this time of year, you may have wondered what you are reacting to. Below are some pictures taken today and fun facts about common allergenic plants in the Nashville area this time of year.
Grasses are prominent allergens in Nashville from late spring until fall frost. These include Northern pasture grasses (Kentucky blue grass, fescue, Timothy, and others), as well as more heat-loving grasses like Bermuda grass, Johnson grass, and Bahia grass. This is one of the reasons I point out when asked why allergies are so bad in Nashville; we are on the border between Northern and Southern grasses and consequently have both!
Johnson grass is instantly recognizable this time of year. It looks like regular grass, just scaled up. Here is a nice stand, some of which is over 6 ft tall. It is in the same genus as sorghum (as in sorghum syrup) and is also closely related, as its appearance suggests, to corn and sugarcane. It spreads by runners and quickly establishes itself in unmowed areas.
The other prominent group of summertime allergens apart from grass is weeds (by which allergists mean non-grass, non-tree plants that are important causes of allergy). We are not into ragweed season yet (more to come on this when it starts pollenating in August!), but a number of other weeds are contributing to allergy symptoms this time of year. Below are pictures of two of the most common weeds, English plantain and black seed plantain. These closely related plants grow very well in disturbed soil, and consequently are found close to us in our yards, gardens, and mowed fields.
English plantain (center of the picture) in its natural environment--nestled among other plants in a lawn. Its fondness for disturbed soil makes it a marker for human activity, and the remains of its pollen in sediments is used as evidence of ancient human agricultural activity. The fact that it grows well near to us contributes to its importance as an aeroallergen.
Black seed plantain, also nestled in a lawn. This native of North America is one of the most common weeds in our lawns and also a contributor to summertime allergies.