Fall Fertilization: Drought vs. Saturation — Why Twin  Cities Trees Are Stressed in Late Summer  

If you noticed trees showing early fall colors, you’re not alone. While we expect rich reds and golds in late September, early color change beginning in August often signals that trees are stressed; it’s not seasonal magic. In 2025, Twin Cities trees are feeling the effects of two  extremes — drought and saturation — and both can harm their health heading into winter. 

Why Trees Are Stressed This Year 

1. Drought stress 

Extended dry spells mean soil moisture is depleted,  especially in sandy soils that can’t hold water. Roots  struggle to take up enough moisture, leading to  wilting leaves, early color change, and reduced  growth.

2. Saturation stress 

Heavy rains or poorly draining clay soils can cause  the opposite problem — waterlogged roots. Without  enough oxygen, roots weaken and can’t absorb  nutrients, leaving the tree vulnerable to disease. 

3. Late-summer impact 

By August, the combination of summer heat and  inconsistent moisture depletes trees’ stored energy.  This is when you might see sugar maples, birches,  and stressed oaks turning color weeks ahead of  schedule.

The Role of Fall Fertilization 

Fall is the ideal time to replenish nutrients. Fertilizing in  late September to early October: 

• Supports root growth before the ground freezes 

• Replaces nutrients leached out during heavy rains

• Helps trees store energy for spring leaf-out 

For the best results, aerate compacted soil before  fertilizing so nutrients can penetrate deeper. 

Watering Tips for Different Soil Types 

Every soil type in the Twin Cities behaves differently, so  your watering schedule should match your yard’s  conditions: 

• Sandy soil (drains quickly) 

◦ Water deeply every 4–5 days in dry weather. ◦ Apply mulch to conserve moisture. 

• Loamy soil (balanced drainage)

◦ Water once or twice a week, allowing the top  few inches to dry between watering. 

• Clay soil (holds water) 

◦ Water less often but for longer periods to  encourage deep roots. 

◦ Avoid frequent, “shallow” watering to reduce root rot risk. 

Pro tip: Water early in the morning so leaves dry quickly  and less water is lost to evaporation. 

Soil Aeration is Important

Compacted soil prevents both water and fertilizer from  reaching tree roots. Late summer or early fall is a great  time to:

• Use a core aerator for lawns around trees 

• Loosen mulch and add organic matter to improve  infiltration 

• Avoid piling mulch against the trunk (mulch  volcanoes trap moisture and invite rot) 

Takeaway

Early leaf color isn’t just autumn showing up early — it’s often a  sign that trees are struggling. By adjusting your watering schedule to your soil type, aerating compacted ground, and applying fall fertilization, you can help your trees recover from a stressful summer and enter winter  stronger.

-Wes, Certified Arborist Shadywood Tree Experts

Exceptional properties deserve exceptional care. Our certified arborists provide complimentary evaluations year-round, ensuring your trees remain healthy, safe, and beautifully maintained. Schedule a visit and experience a level of service that matches the quality of your home.

I’ll address some common pruning questions that we receive at Shadywood Tree Experts. If you don’t see your pruning question here please call our office at 952-933-0614 and we will connect you with one of our consulting arborists to help you with all your tree care needs. 

Does removing dead branches improve the health of our trees?

Answer: No. After a branch dies, a process inside the tree begins where a chemical barrier forms to prevent decay from entering the tree. This process is called compartmentalization. The branch is no longer connected to any of the tree vascular tissue and cannot draw from any of the tree’s resources. So, leaving dead branches has no effect on tree health. Dead branches are removed from trees because they can be unsafe or they are aesthetically displeasing.  

How often should trees be pruned?

Answer: Trees are pruned for many reasons. If you are pruning for clearance over your house, or over the lawn or driveway; then your pruning frequency will be based on how fast your trees are growing. Tree branches can grow from 4 inches a year up to 18 inches per year depending on the species. 

If you are pruning to mitigate risk of dead branches falling, then the pruning frequency will be based on the types of trees you have and how often they produce dead wood. Ash trees often go through a “restructuring” process where they shut down non-productive branches about every five to six years which results in hanging deadwood in the trees. If you have any ash or similar tree species, then it makes sense to plan on pruning every five to six years. The idea is to plan your pruning on what particular species of tree you have. 

Hazardous broken and hanging branches are quite often caused by wind events exceeding 20 miles per hour impacting weak spots in the trees. When these wind events occur then it’s a good practice to have your trees evaluated after these events for broken and hanging branches as well as any structurally deficient tree parts that could pose a risk for falling. 

Deadwood in your tree that’s two inches in diameter or larger is considered hazardous. If these branches are over infrastructure that would be harmed by the branches falling, then these branches should be dealt with in an expedient manner. So too, should branches with obvious defects. The longer a dead branch is left in the tree, the more likely the branch is to fail. Have these branches looked at when you notice them and formulate a plan. An experienced consulting arborist can help you identify all of the areas of concern in your trees and come up with a pruning plan that will meet your objectives. 

Our trees hang down over our house and touch the house, what should we do?

Answer: Have a certified arborist inspect your trees. A basic inspection should include identifying the tree species and their location as well as their distance from structures and power lines as well as their current condition. Estimate that branches grow about a foot a year (that’s an average, some are faster, some are slower). If the branches are touching or rubbing then you’ll have to take action. If the branches are 6 feet away then you probably have 5-6 years to do something. Remember, a tree has to grow every year to stay alive. If you have trees close to your house then you want to have a plan on how to train the tree to grow up and away from your house. It is generally a poor idea to remove large branches from trees close to structures as this leaves large wounds on the trees. Discuss the potential drawbacks of this with your arborist. If a tree has been planted or left to grow in a poor location, your arborist may recommend removal as a way to prevent future problems. 

Shadywood Tree Experts have experienced consulting arborists who can answer all your tree pruning questions and help you develop a comprehensive pruning plan for all of your landscape trees. Call us at 952-933-0614 to schedule a free visit. 

Jake Nitz ISA Certified Arborist #WI-0761A

Why Ash Trees are valuable (and why EAB is a problem):

• Minnesota has nearly one billion ash trees, according to the MN DNR.

• Ash trees were often planted to replace American elms lost to Dutch elm disease. 

• Ash, especially black ash, is an important species to our state's lumber industry.

• Emerald ash borer, a small insect, attacks all ash species: green, white, and black.

• Basically, it's a near-extinction event for ash trees in North America because they have no natural defenses against the insect.

• EAB population is currently peaking in the Twin Cities area with the vast majority of untreated ash trees declining rapidly or already dead.

• The only defense against this invasive and deadly insect is preventative treatment by a certified arborist.

Emerald Ash Borer (EAB) History:

• Globally: EAB is from Northeastern Asia where it only attacks weak ash trees; healthy ash trees can fight off EAB.

• Nationally: It first appeared near Detroit in June 2002, though experts think it was actually here since the 1990s.

• Locally: Found in St. Paul near the U of MN campus in May 2009.

Spotting EAB Symptoms:

• Starts with the top of the tree looking thin.

• Within 2-3 years, the upper canopy is mostly dead, but you might see a flush of healthy-looking growth lower on the trunk.

• The bark in the upper parts can look splotchy, called "blonding."

• Emerging adults make the distinctive “D” shaped holes, often more visible on medium sized branches.

• Tree death usually follows quickly, about 3-4 years after the EAB attacks.

What is an Emerald Ash Borer?

• Adult insects are slender, ⅜ inch long, emerald green in color and rarely seen.

• Cream-colored larvae are found under the bark feeding on the inner bark and cambium. They are slender as well and ½ to 1½ inches long.

• Larval feeding causes “S” shaped galleries, preventing water and nutrient movement in the tree, which is what eventually kills the tree.

What Can You Do About Emerald Ash Borer: Treat or Remove Ash Trees

• Slow the spread: do not move firewood. In other words, do not take firewood to your cabin. The majority of northern Minnesota counties are under EAB quarantine because of this.

• Treat your ash trees. If you are not treating your ash trees, they will die from EAB. 

• Missing even one every-other-year scheduled treatment can lead to serious decline and possibly death of your ash tree.

• If you haven't started treating by now, it likely is too late to save your ash trees.

How Shadywood Can Help:

• We have been protecting ash trees since 2009. We are the experts!

• We offer all the latest EAB treatment options.

• Our arborists are full-time, year-round professionals who will check out your ash trees before recommending a treatment plan. 

• Removing EAB-affected ash trees is risky because their branches far more quickly than other recently-dead trees become weaker and more brittle. Our team has the training, experience, and equipment to remove these trees safely and efficiently.

• We offer full tree pruning, removal and stump grinding services. In addition, our plant health care division can care for your valuable trees, evaluating their health, creating customized health programs to keep these trees healthy and flourishing for as long as possible.

The Future of Ash Trees:

• EAB is seriously changing the look of our streets, parks, and wooded areas.

• In just a few years, ash trees will be a rare sight in Minnesota's towns and forests.

• In Northern and central Minnesota, a valuable lumber resource will be lost.

• Research and testing is being done to find ash trees that are naturally resistant