Ask SAM: Cactus spreads when broken

This column is provided by Larimer County Extension's Small Acreage Management (SAM) Program to assist rural residents.

Dear SAM,

What can I do to keep cactus from taking over my property?

Thornton

Dear Thornton,

Cactus is part of our native prairie vegetation. The two most common types are prickly pear and hedgehog cactus. Both produce colorful flowers, often yellow or greenish, from May through July.

With a healthy plant community, you can expect to find a few cacti scattered on your property. When they start taking over, it's time to think about why.

Some cactus species can spread when pieces of a plant are broken off. When a passing deer knocks a pad off a prickly pear, that pad can grow roots and develop into a new plant.

Livestock on a pasture can have the same effect as a herd of deer. All those hooves running around can result in dozens of new cacti.

Cactus is a plant that should not be controlled with mowing. Imagine how many deer that bush hog mower represents! While most of the chopped up pieces will desiccate and die, enough could survive to create a cactus infestation. Consider this before mowing to control weeds or manage your grass.

The same is true of harrowing. Never harrow a field if you are concerned about an increasing cactus population.

Cactus infestations, like many undesirable plant problems, can be caused by overgrazing. As grasses are weakened from excessive grazing, more water, nutrients and light become available to the cacti. Think of it as a garden where the animals are pulling out the grass to make more room for the cacti.

After you correct any management problems, you might have to reduce the existing cactus population to bring it back to a tolerable level.

You can dig the cactus with a shovel. Place the removed plants in a bucket so they can be burned or otherwise disposed of. If you leave them on the ground, they might take root.

If you choose to use herbicides, picloram (e.g. Tordon 22K) is recommended. Picloram is a restricted-use pesticide, so a private pesticide applicator license is required to purchase the concentrate.

Spot spray the plants you want to kill. Unless the infestation is especially severe, broadcast spraying is unnecessary. Picloram will kill many broadleaf plants, so avoid spraying desirable species.

Do not expect fast results. Cacti are slow to absorb herbicides. Use a surfactant to help the herbicide penetrate the plant. Adequate control may take one or two years to achieve.

For more information on cactus control, go to http://wildlife.tamu.edu/publications/L5171.PDF.

SAM

Have a question about rural living? Write to Ask SAM, Larimer County Cooperative Extension, P.O. Box 543, Fort Collins, CO 80522.