There are some avid walkers residing in this region! An who could blame them? The trails of Afton, Hastings, Lake Elmo, Cottage Grove, and surrounding areas are magnificent. They lead rovers through prairies, beside rivers, over mounds, and into woodlands. Perhaps readers have gone for a stroll in recent weeks. If so, they may have noticed something unusual. Brown, crunchy leaves are blowing about in Mother Nature already.

Joe Zeleznik is the Extension Forester at North Dakota State University. In a 2007 issue of the North Dakota Climate Bulletin, he elevated the scientific reasoning behind fall colors. Chlorophyll, carotenoids, anthocyanins, and tannins are groups of biochemicals. The levels of each chemical begin to vary each autumn. When this occurs, canopies appear yellow, red, brown, and orange.

Just as Minnesotans are photographing their warmtoned backyards and parks, leaves descend from trees. Due to the days becoming briefer and chillier, hormones in select trees deliver chemical messages to their leaves. Then, abscission cells gather at the end of stems. At a slow rate, the cells repel the leaf from its branch. The tree quickens the separation. Finally, a gust of wind thrusts the leaf from where it grew.

Sverre Sandgaard is the Natural Resources Manager for Carpenter Nature Center. He holds a degree in natural resources and forestry. In addition, Sandgaard was born in, raised in, and is a current resident of Cottage Grove, MN. He led The Journal down a path and past several trees at Carpenter Nature Center on August 18. When adjacent to an elm tree that was shedding leaves, The Journal questioned, “When will leaves usually leave this sort of tree?”

“Much later…usually you’re looking at mid-October,” Sandgaard answered. “Again, it kind of just depends on the year… it could be a lot of things.”

One of the reasons a tree may rid of its leaves earlier than normal is if it is stressed. The drought in Minnesota has been aggravating species this summer. Data from August 10 revealed that a portion of Washington County was in a D1 moderate drought while the remainder was in a D2 severe drought. Areas in the midst of a D1 drought experience abnormally miniature rivers and lakes in terms of depth. D2 droughts have many more dangers. One of them is noted on the U.S. Drought Monitor. It reads, “Landscaping is stressed; leaves change colors early.”

Early leaf loss could also be the outcome of a perishing tree. Sandgaard used ash trees as an example: “Right now…probably part of what you’re seeing in Cottage Grove is the Emerald Ash Borer. There’s a lot of ash trees…in Cottage Grove. I have a lot of big ash trees that have been there forever and…they just don’t look right, there’s a lot of dead branches.”

When arid conditions and the risk of disease or infestation are combined, a tree is further endangered. Sandgaard proved this point to The Journal with an illustration: “It’s the same thing with a person. If you’re hungry and lack nutrition [and] you lack maybe not a lot of clean water… And then I come in and I’m some disease, it’s gonna hurt you more than a normal healthy person.”

While Sandgaard highlighted the organisms that were suffering, he educated The Journal on ones that were thriving. A sugar maple, for instance, appeared “fine.” Sandgaard indicated that its location is a common area for stormwater to flood in. Therefore, the sugar maple was moisturized. Sandgaard contributed additional insight to its success: “They obviously don’t have any disease currently going after them so, that’s for sure,” Sandgaard added.

In conclusion, if readers in close proximity to Cottage Grove witness fall colors and descending leaves before late September/early October (declared the “typical date for peak fall colors” for southern Minnesota by the Department of Natural Resources), they should not fret. Rather, they can invest energy into maintaining their trees. This is the guidance that Sandgaard desired to elevate: “Try not to prune in the summer…Try to prune any tree when it’s in its dormant period. Basically, late fall; winter is the best time; early spring before they start growing again. That way you’re not likely to spread any diseases.”

In the 1980s, ash trees were introduced to Cottage Grove. Sundgaard labelled them as a “hearty” that “grows fast.” Today, they are being killed by Emerald Ash Borer and their leaves are falling.Photo by Sadie Jones

Amidst the drought, this sugar maple has yet to go into dormant. Its leaves continue to produce chlorophyll. Photo by Sadie Jones