You may have noticed a lot of the grass stimulated by this spring’s moisture is now turning purple at its top. That is Downy Bromegrass (Bromus tectorum) more commonly referred to as “Cheatgrass.” As soon as temperatures stay hot it will dry out and become one of the most aggressive flash fuels on the landscape. It also tends to reduce the dominance of desirable native species since it starts early and spreads seed aggressively. Another plant which is obvious this spring is the Yellow Sweetclover which is emerges heavy after earlier moisture springs. This plant has a lot of pollen, fixes nitrogen in the soil (fertility enhancer) but also contains high levels of Coumarin which can generate bleeding internally if large amounts are consumed.
So how do you manage these plants? Both can be controlled with herbicides at different times. But many landowners first consider mowing these plants to regain aesthetics and desired condition. There are a few safety guidelines to follow when mowing at any time.
Consider running your mower a little higher than on lawns. This will reduce damage to desirable grasses so that they still have enough leaf matter to conduct photosynthesis leading to strong roots. It is possible to “overgraze” with a mower by running too low to the ground. Also running the mower a little higher reduces the chances of hitting debris, rocks and critters such as snakes. This not only reduces strain and wear on your mower but also reduces the chances of generating a spark which can ignite a wildfire in “flash fuels” such as cheatgrass.
If you are going to mow cheatgrass, considering doing it while the plant is still green so the seeds are not ready to be spread by the mower. Also mowing green plants early in the morning when humidity is high, temperatures are cool, and wind is down reduces chances of wildfire starting and spreading. Best practices recommend walking the field to identify safety risks before you mow. Wear appropriate boots to prevent bites from assorted residents and make sure to remove or mark possible debris.
Once you take your clean mower into a location to mow make sure that you clean it and your clothing off before you leave the site. This will prevent spread of your problems to new areas. If you have mowed down heavy accumulations of problem weeds consider bagging them and disposing of them. After you mow – clean the equipment at the site to prevent seed spread.
It is possible to impact weedy species by repeated mowing but you can also impact the desirable species on site and generate heavy moisture loss due to lack of litter and ground cover. Annual problem plants are easier to control with mowing than perennials but you need to investigate if the target plants reproduce by seed, runner, or both. If it’s by seed impacting those plants before their seeds form is crucial.
Remember that mowing with a sharp blade spreads less weed seed than using a dull blade and simply “beating” the weed into submission. Keep your hands and feet clear of risk areas on the mower and keep all factory installed guards in place and in good condition. If operating on a gravelly or stony site take note of where your mower can throw stones. Spectators need to be well clear of that range – especially short spectators like children.
“Mulching” mowers often drive plant material and seeds back to the soil. In the case of species like Downy bromegrass this just helps it get thicker. This species is a challenge and may require application of a product like Plateau in late summer/ early fall to get control. Cheatgrass has had trials to graze off the seedheads or mow them only to adapt by forming seeds at a lower level. The USDA Ag Research Service is testing several bacteria which have potential to control cheatgrass.
If you are mowing in the sun and heat remember protection, but avoid distractions like cell phones, music players and radios. You need to pay attention while mowing.
Make sure your mowing efforts to “improve how things look” don’t make it worse the next season by propagating more weed establishment. Remember that mowing is all about approach and timing. Consider safe and early for your efforts. Happy field cutting.