Musk thistle expanding across region

PNT Staff Report

There are different weeds that are native to New Mexico, but some weeds like the musk thistle are trying to take over. The musk thistle is a tall plant with waxy dark green deeply lobed leaves with spines. The leaves can appear to be white to silver-gray.

Michael Roberts, a U.S. Department of Agriculture agronomist, said he doesn’t know how the musk thistle was introduced to the U.S., but it is an aggressive weed.

“I think it was back in the 30s or 50s when they got here,” Roberts said. “But they have just exploded in the last five to 10 years.”

The weed has spread to 45 of the lower 48 states in the U.S., including New Mexico, without the presence of natural enemies.

Roberts said any plant in its natural environment has enemies like the boll weevil or a bug that naturally keep it in check.

“When you take it out of its natural ecosystem, it has a chance to just go crazy,” Roberts said. “They are really tough plants and it doesn’t take much water to get them started.”

One plant can produce up to 10,000 to 20,000 seeds, which look like cottonwood seeds and can float a short distance. The weed begins to spread seeds about two weeks after first blooming in mid to late spring. It blooms from 7 to 9 weeks.

“They’re such a big deal as far as spreading that I don’t think people realize how bad they are,” Roberts said. “People see them as pretty wildflowers, they might take them home and try to plant them.”

The weed can grow up 2 to 6 feet high and 2 to 5 feet wide. The plant can choke out grass and other vegetation in the area. Once the weed dies, it leaves a bare place in the ground.

“Normally in a place where grass would be, you got that open, bare ground exposed to erosion,” Roberts said.

There are also chemicals that can be used to kill the plant, but Roberts advises using a minimal amount because there are some thistles in New Mexico that are endangered.

“The only way I know to remove them is to hoe them or go out there and chop them off at the ground,” Roberts said.