Questions are coming into OSU Extension offices about masses of white, cottony, fiber wafting through Ohio’s forests and landscapes. Charles “Chuck” Behnke, retired OSU Extension educator, was known to call the diaphanous fluff “Mother Nature’s navel lint.”
There’s some truth to Chuck’s metaphor because the culprits behind the fibrous phenomenon are female eastern cottonwood trees (Populus deltoides, family Salicaceae). Cottonwood trees are dioecious which means there are male and female trees. Monoecious means male and female reproductive organs are found on the same tree.
Small male and female flowers form on short, pendulous stems hanging from twigs; a flower arrangement called a catkin. Pollen from the catkins on male cottonwood trees drifted on the wind to pollinate female flowers in early spring.
Once pollinated, the female flowers developed small, green seed pods that have now split open to shed tiny seeds surrounded by fibrous strands of white “cotton.” The filmy fibers carry the seeds aloft and give the cottonwood its common name. Seed production appears to be unusually heavy this year throughout Ohio.
Cottonwood cotton seems to be appearing everywhere. Coupled with the "Year of the Aphid" with sticky honeydew spewed onto everything, the fiber may occasionally present a diagnostic challenge.
Aside from asking for an identification of the cotton-like fluff, Ohio landowners may state that they’ve never seen the fluff drifting around their landscapes before. Owners of cottonwood trees may remark that their trees never produced cotton before.
Changes in wind directions may explain why cottonwood fluff is appearing in unexpected places. Our prevailing winds blow from west to east across Ohio. However, winds have been blowing from the north for the past several days possibly driving cottonwood cotton into locations where it was not commonly deposited in the past.
If a cottonwood tree owner says they’ve never seen their tree produce cotton before, it’s important to ask about the age of the tree. It takes several years for female cottonwood trees to mature to produce seed.
Another common question is whether or not the cottony material will contribute to nasal allergies. Apparently, there’s no evidence that cottonwood cotton triggers allergic reactions. If people are currently suffering from hay fever, the source would be another allergen such as wind-borne pollen from grass, weeds, and other trees.
However, the male pollen from cottonwood trees that blew around earlier this season can produce hay fever symptoms and the result is nothing to sneeze at. According to the May 3, 2003, issue of the New Mexico State University’s Southwest Yard & Garden newsletter, “Because of their pollen, the male varieties of poplar (the genus Populus, which includes the cottonwoods) are banned in Albuquerque.”
Cottonwood cotton from the female trees is usually just a short-lived nuisance. However, massive quantities of the fluff may clog air conditioners, car radiators, and swimming pool filters. Also, the delicate fiber is highly flammable, so it can be hazardous around open flames.
Wild eastern cottonwoods are commonly found growing near streams and rivers. The shade provided by the fast-growing trees with huge, spreading branches is appreciated by anglers and picnickers.
The downside is that fast growth means weak wood. Cottonwoods are notorious for dropping large branches. It’s best to vacate the area during high winds.
Still, eastern cottonwoods have their place if planted in the right spot. They are tough trees that are tolerant of drought and a wide range of soil pH. The cotton problem can be solved by selecting “cottonless” cottonwoods such as the cultivars ‘Siouxland’ and ‘Sparks’ as well as the hybrid Populus x canadensis ‘Robusta’. These selections also have other valuable qualities not found in the straight species.