Stressed trees changing colors in South Dakota

SIOUX FALLS, S.D. (KELO) — The southeast portion of South Dakota has been under a state of drought for much of the past several months, and for some of the largest living organisms in our communities, that lack of moisture is causing stress.

Driving around, whether you’re in the Yankton area, Sioux Falls or Mitchell, you may have noticed a peculiarly autumnal sight, leaves beginning to change color, despite temperatures in the 80s and 90s.

You haven’t lost a month or two, and your eyes are not deceiving you. Certain trees are beginning to change color, and according to John Ball, Extension Forestry Specialist with SDSU, that’s a bad thing.

This shift in color in the region began within the last few weeks of July, Ball said, which means the color change has begun around two full months early. “Normally we’re gonna get color when we start getting a good frost,” Ball said. “We haven’t got a good frost yet. This is all due to stress.”

That stress is attributable to two main issues in the southeast, Ball said. Drought and aphids.

“The long-term drought has stressed the trees — and we’re seeing an abundance of aphids,” Ball said, explaining that these bugs strip the sap from the leaves of trees. “Both these, and often in combination, are a stress on a tree.”

Stress in trees, particularly this time of year, manifests in the form of premature fall coloration.

Ball said this color change is often marginal, causing discoloration just at the edges of the leaves, or just in the outer reaches of the branches.

“The reason for this is that the trees are not keeping up with the normal production of chlorophyll,” Ball said. “That’s the normal green color.”

“When trees get really stressed, they can stop producing chlorophyll as a means to conserve energy for the survival and wellbeing of a tree,” explained Bryan Peterson, Urban Forestry Specialist for the City of Sioux Falls.

This conservation of energy due to drought is causing more yellows and reds to come out in the leaves, and in some cases is even causing leaves to fall.

Ball predicted that if we continue through the summer with very little moisture, we’ll likely be looking at a fall season with few leaves left on trees. If we get plenty of rain, the leaves are likely to stick around, though they will remain changed in color.

One additional effect that an increase in rain could have, according to Ball, is that trees which have begun to drop leaves could begin to sprout new ones. “That’s not good,” he said. “That foliage is coming on in hot, dry conditions, and it’s coming on too late.”

Both Ball and Peterson recommend tree watering as the best remedy for trees experiencing this change in color.

While watering will not bring back the color in the leaves, it can help with long term health of the tree.

“Longer term, if the trees do drop leaves, you still want to water them,” said Ball. “If you don’t what you may see is what you saw this year.”

Ball said the dry conditions last year lead to a lot of trees drying out, “so this spring there were a lot of maples and birch — that the top of the trees were bare and have since died back.”

If this happens, the best case is that the tops of your trees merely take a few extra weeks to months to put on leaves, but there’s also a chance that the twigs themselves die out, leaving the entire top of your tree dead.

When if comes to watering a tree, there is a wrong way to do it.

“[A lawn sprinkler system] is wonderful for grass and turf, but it does not effectively water trees,” said Peterson. The issue, he explained, is that lawn sprinklers are set up to water grass, which prefers continuous but shallow watering.

Trees, meanwhile, require more spaced out yet deeper watering. “To get enough water to soak into that top 18 inches of soil you would have to run your irrigation system for many many more hours than you would for your lawn,” Peterson said.

Running your sprinklers for a period of time long enough to impact your trees would likely result in a flooded lawn, and an extremely high water bill.

Instead, Ball recommends using a hose and/or a sprinkler to water for a half hour. “Push a screwdriver into the soil, and hopefully it’s moist down about six-inches — then you really don’t need to water again until you push it down and it’s dry down to six inches,” he said.

If you’re not up to the idea of watering your own tree, or worried about whether you’re doing it right, Peterson recommends contacting an expert. “We do put out a list on our website of all the arborists that are licensed in the city,” he said.