How to get rid of cottonwood trees

Q We had a 30- to 40-year-old cottonwood tree on our property. Several years ago it became diseased and unfortunately we were not able to correct the issues and she died. About six months ago, we had it removed and stump ground. About two months ago, our yard started to spout growth from the root system of the tree that has spread nearly 50 yards from the site of the cottonwood. The more we mow or even rip them out from the root, the faster the growth grows.

My question is pretty simple but I do not know if the answer is: How do we remove or kill the roots? We have a sprinkler system so I cannot rotor till the entire yard. Is there something that I can apply or spray? I have not watered the grass at all and still they grow.

Jason R.

A The cottonwood tree sprouts grow in response to the removal of the large tree. That is their survival mechanism for dealing with their flood plain habitat. As an old tree washes away, the roots left behind sprout to fill the void left by the old tree. These sprouts draw nourishment from the roots of the old tree until they develop their own root system. This is what you are noticing as the compensatory regrowth and the reason you want to kill the roots.

A systemic herbicide applied to the sprouts that will translocate into the root system can be used to speed the death of the roots, but that will take time. Such chemicals do not kill the whole root system. Cutting the sprouts at or below ground level each time they sprout (within a couple of weeks of their appearance) will also work, though it may take a little longer. The principle behind each of these methods is to allow the sprout to grow, extracting stored food from the root, and then to remove the sprout and the food it extracted to ultimately deplete the food stores in the root. The length of time to accomplish this depends on the size of the root and the stored food reserves.

In time, with cutting of the sprouts, decomposing fungi will enter the old roots if these fungi are not already there. The food reserves in the roots will deplete even faster as the fungi consume the dying roots. Anything you do to encourage the fungal growth — such as providing moisture and nitrogen fertilizer for the lawn — will enhance the depletion of the root food reserves. If you allow a sprout from the roots to remain too long before removing it, the sprout will begin storing food in the roots underground. This will allow the roots to support development of sprouts for a longer period of time.

Persistence is the best "herbicide" whether you use chemical controls or physical removal of the sprouts. Frequent removal of the sprouts during the growing season will ultimately (within one to two years) result in success.

Send your gardening questions to Yard and Garden, Attn: Dr. Curtis Smith, NMSU Agricultural Science Center, 1036 Miller Rd. SW, Los Lunas, NM 87031. You may also send to [email protected] or leave a message at https://www.facebook.com/NMSUExtExpStnPubs.

Curtis W. Smith, Ph.D., is an Extension Horticulture Specialist, retired from New Mexico State University's Cooperative Extension Service. NMSU and the U.S. Department of Agriculture cooperating.

NEW BRIGHTON, Minn. -- It's a pretty-looking problem plaguing yards across the Twin Cities. And you must be careful about how you get rid of it.

Cottonwood trees are shedding and that has some yards looking like we're in January instead of June.

"I don't know if there's a tree truly that's not a nuisance, but this one can kind of get to you after two weeks," said homeowner Amy Lee.

Frustrating fluff coats her yard and that of her neighbors. A gentle yet overwhelming reminder of the type of trees that tower above.

"I would guess that because of the lake there's probably 75 cottonwoods in this circle," she said.

The cottonwood seeds are in drift mode in Minnesota, piling up like snow on driveways, lawns and along roads.

"They're highly flammable," said Fire Marshal James Lange of the Fridley Fire Department.

He's seen the damage firsthand when he said a homeowner tried to burn the cottonwood fluff as a means of removing it.

"And then [the fire] went across their lawn, jumped the fence, burned up their fence, went to their neighbor's yard, their other neighbor's yard. And then it burned up a deck, burned up a shed," Lange said. "They thought it's just gonna burn this little area, and it travels just like lightning, just very fast and very difficult to control once it gets into the woods."

Several years ago, YouTube videos of people lighting cottonwood on fire sparked a small spree of frees in Coon Rapids. The fire department there responded to half a dozen fires in a two-week span.

To safely get rid of the fluff, Fire Marshal Lange suggests using a rake or leaf blower.

"We have a sprinkler system, so every other day we get up and the cotton has kind of been melted down into our lawn, so that helps a little bit," Lee said.

Water can also be helpful when it comes to your air conditioning units. When turned on, they suck up the cottonwood floating in the air. It can clog the unit, making it worker harder than it should.

To clean the cottonwood, HVAC companies suggest hosing it down with water. Just make sure to turn the unit off at the thermostat or by removing the power pin next to the unit outside.

Given the amount of cottonwood trees near her home, and the high temperature, Lee estimates she hoses her AC unit down every other night.

After washing the cottonwood out of your AC unit, turn it on to make sure it's properly cooling your home. If not, you might need to call a professional to check it out.

Jeff Wagner

Jeff Wagner joined the WCCO-TV team in November 2016 as a general assignment reporter, and now anchors WCCO's Saturday evening newscasts. Although he's new to Minnesota, he's called the Midwest home his entire life.

How do you keep cottonwood trees away?

How do you kill a cottonwood stump?

What is the purpose of cottonwood trees?

What's the lifespan of a cottonwood tree?