Tree Health Update – Spring 2021 – Sioux Falls
Spring time is coming on fast. I have been seeing aspen and some silver maple flowering and its only early March. But what is most concerning is the amount of conifers (mostly spruce and pine) that have died or are in bad shape coming into this spring of 2021 around the Sioux Falls area.
Its been a rough few years.
Remember how wet 2019 was? If not, we received over 300% of our annual rainfall that year! It was very wet. And then, southeast South Dakota especially was categorized into a severe drought beginning last late summer (2020). And even though we just got a few much needed weather events to provide some moisture, its not been enough. We are still in drought conditions.
The excess water in 2019 was just as severe and hard on most trees as the drought we are in now. Plant roots need to breath in order to absorb water and nutrients, and they can’t do that if the little air pockets in soil are full of water. So the affect is the same as drought, no water into the canopy. So in reality, the trees have essentially now been in severe drought conditions for more than 2 years!
What I’m seeing.
What is most obvious right now are the spruce and pine trees. Especially those planted within the past few years. I’m seeing spruce dead and dying this spring that looked healthy last fall. Most customers are telling me the trees were green and normal in the fall and by late February the needles were brown and falling off. What happened was the trees were on the verge of death last fall with no moisture. This winter finished them off by sucking the last of the water in the needles out with those few cold windy snow storms we had. Plus, very little snow cover and mild temps, made the water loss within the needles even.
What to expect this year?
Unfortunately, more and more trees will be getting sicker and showing signs of the drought stresses. Those that have already died were the extreme cases. Trees are very slow motion plants when comparing how we live day to day. It can take up to 3 years before a tree would show signs of stress from something like a drought. It all depends on how healthy the trees were going into the stress event. That is why we are seeing the recently planted trees show signs of stress first, they were already stressed from being transplanted.
We can expect more and more trees to show signs of the drought stress (especially conifers). I anticipate a lot more spruce to decline and succumb to the drought within this year. Those that do make it, will have a good chance of being attacked by Valsa Canker(formerly Cytospora), among other diseases. The impact of the drought will be seen less in established deciduous trees. But without a turn around in weather this year, the impacts will be greater.
What to do?
There isn’t anything we can do about the weather. But we can water (correctly) and provide mulch. And those two things are usually the largest limiting factors to tree health in our region.
Watering your trees when its dry is very important. But care must be taken to water with intent and so its available for the trees. Also, be sure to not overwater. More often in not in the urban areas of Sioux Falls, I run across over-watered trees than under-watered.
The water needs to be applied slowly (over the course of hours) but in large amounts (think of an inch of rain). So your lawn irrigation is not adequate and often detrimental. My advice, cut way back on the lawn watering and hand water your trees. Use a tree watering bag, 5 gallon bucket with tiny holes in the bottom, or a soaker hose. Water no more than every 10-14 days after providing as close to what you think an inch of rain would be.
Don’t overthink it, just do your best to make the soil wet and keep it wet. Not soggy, but just wet enough to stick together slightly if you squeeze it in your hand.
Mulching the critical root zone (area under the canopy) is the other part to watering where the trees will benefit. Grass will outcompete a tree for water and nutrients. The difference between a tree that performs well and a tree that struggles is often the difference between good mulching and reducing turf competition.
There should be 2-4 inches of mulch on the ground, evenly spread out, going from an inch from the trunk out to the drip line of a tree (edge of the canopy). If you don’t want to lose that much lawn, at least go out 2-3 feet radius from the trunk (5-6 foot diameter circle).
I like a shredded hardwood mulch. For spruce and pine trees, the mulching should go out past the drip line. Any less and the trees WILL struggle as they get older. Lastly, no weed barrier or anything like that should be between the mulch and soil. The weed barrier fabrics negate the benefits of the mulch (you may as well have grass).
Thank you for reading! Having healthy trees in South Dakota can be a challenge. Especially when the climate favors grass and is as erratic as its been the past number of years. But it is not impossible, it just takes a little more effort and care than other parts of the country. If you have questions on the care of your trees, you can find more resources on my website. Or can reach me via email: email@example.com or call/text 605.759.6020