July 2024 Treecologist Tribune

Welcome to the dog days of summer! I recently learned that the “dog days” were historically those following the heliacal rising of the star system Sirius, which Hellenistic astrology connected with heat, drought, sudden thunderstorms, lethargy, fever, mad dogs, and bad luck. That sounds about right….

We received an intense rainfall of nearly 2 inches at the beginning of June and then no rain whatsoever until June 29. Luckily, the dry spell ended in July—we have received approximately 9.5 inches of rain during around 7 rainfall events from June 29 through July 26. But we have to take this with a grain of salt, because rain doesn’t necessarily replenish life. First, rain must soak into the land to benefit trees, soil, and other lives that need it. Unfortunately, most of the suburban landscape has no soil to hold this rain, and instead, the water rushes downhill across the surface, causing flooding as we’ve seen recently across the Triangle. Soil is the sponge that holds water, and, without it, the land becomes barren and susceptible to drought. Alan Savory said it best when he stated: “It’s not drought that causes bare ground, it’s bare ground that causes drought.”

During early July, it was also very hot. High temperatures are common in NC, but it has been a bit hotter than normal. There have been 9 days where temperatures hit or exceeded 100 degrees. The record for the most 100-degree days in RDU is 12, set in 1999. On July 5 this year, the temperature was 106 degrees, the hottest day ever recorded in NC’s history.

From the standpoint of a tree, the speed at which we transitioned from a spring with mild weather and fairly plentiful rainfall to a full-fledged summer with intense heat and no rain was devastating. While most trees are suffering right now, those growing in poor soil conditions are in bad health and dying in droves. This is especially true for young trees planted in the last several years. Being stressed also makes them vulnerable to pest attacks, which creates even more issues. As avid readers know, the solution is to promote healthy soil by doing the following:

• Add 3-12 inches of arborist wood chips extending from the trunk to the edge of the canopy.
• Leave the leaves that fall from the canopy in this bed to rot every year.
• Feed the soil in this area under the tree with compost and compost teas.
• Plant native small trees and shrubs in these beds to promote even healthier soil and the exchange of nutrients between the tree and these additional plants.
• Do not harm the life in the soil under/around the tree by using traditional fertilizers, harmful pesticides, herbicides, mosquito sprays, and other products that cause death.

Building soil takes time, but it’s worth the investment. As we build deeper, healthier soil, it holds more water and boosts the health of all plants rooted in that soil. This becomes a positively reinforcing cycle leading to more, positive outcomes at a faster pace. If we could do this throughout the Triangle, we would see local temperatures cool, and rainfall would become more frequent and less intense during the growing season. This is also true on national and global levels. You can learn more about this in my book, From Wasteland to Wonder. For those wanting a deeper dive on the topic of how trees and soil affect and are affected by local water cycles, I recommend the book Water in Plain Sight, by Judith Schwartz.

We could also talk about how structural pruning and inspections are so important right now, particularly in light of severe storms and hurricanes. But we have covered these topics in depth recently. Instead, we’ll pivot to something fun, and then I’ll answer a reader’s question.

Something fun: I recently had an insightful discussion with Matt at YourForest podcast. It’s one of my favorite podcast conversations thus far because we had no pre-set agenda and no time constraints. I highly recommend it! If you want to hear other podcasts featuring me, you can search my name on Spotify, and you can also find some linked from the book page.

Now let’s turn to a question from Ashely. She writes, “I would love to hear any tips you have to make the process of watering easier.” This is a timely question! When it comes to watering trees and shrubs, I offer the following insights and ideas:

• The rule of thumb is that a tree needs approximately 10 gallons of water per inch of trunk diameter per week during the growing season. So, a tree with a 12” trunk diameter needs ~120 gallons of water per week.
• Figuring this out can be challenging, so you can use my approach: Feel the soil with your fingers. Grab a pinch from under the arborist wood chips beneath the canopy and roll it around in your fingers. Is it dry and dusty? The tree needs water. Is it damp and holds a bit of form? No water is needed. Is it sopping wet and muddy long after any watering or rain event? Your tree is receiving too much water, which is just as bad as too little water because the roots can drown. Roots need oxygen and other gases just like we humans.
• Watering should be frequent and slow versus infrequent and fast. This allows the water to seep down into the ground.
• If possible, use well water or rainwater captured from your roof to water your trees and shrubs. Municipal water often contains harmful chemicals that are less than ideal. That said, even municipal water is better than nothing for a thirsty tree.
• For watering, I recommend an open-ended hose rather than a sprinkler system. The sprinklers can cause disease issues by repeatedly splashing water on the trunk and foliage.
• You can use a product like a tree-watering bag. These have the advantage of releasing the water slowly.
• Better yet, try this great approach my colleague Nora taught me: Clean a used milk jug and use a pin to prick a few holes in the bottom. Fill the jug with water and place it underneath the canopy of your tree, near the trunk. This will slowly drip water into the roots. This is a free product that reuses waste and delivers water slowly—a triple win!

I hope this is helpful. Please let me know what questions you have, and I’ll answer them in future editions of this newsletter. Also, please let us know if we can help care for your trees during this hot growing season—we would love to be of service!

Until next time, my friends!