When maintaining a native plant habitat for monarchs or other pollinators, proper management is a must. Mowing is one practice that can help control woody vegetation or weedy species and prevent undesirable species from setting seed if timed appropriately. It is important to apply pollinator-friendly best management practices when using any habitat management technique, such as mowing, grazing, prescribed fire, or pesticide application.
Best Mowing Practices for Monarchs
Mowing can be an effective management tool to control woody and weedy species and manage undesirable species from setting seed. Mowing also may stimulate the growth of desirable nectar plants. However, mowing too often or during certain times of the year may result in higher mortality for wildlife, including monarchs and other pollinators. Monarch eggs, larvae, pupae and even adults may be killed directly by the mower, and mowing can remove critical habitat for monarchs and other species. To limit monarch mortality, use the following recommendations:
- Avoid mowing the entire habitat. Leaving refuge areas for wildlife will allow for recolonization of the mowed site. Leave areas that may be good nesting or overwintering sites (leaf litter, dead stems, other ground cover) for pollinators or other wildlife. Marking habitat areas may prevent accidental mowing, and signage helps communicate why an area is not mowed.
- Avoid mowing monarch habitat when monarchs are present (see Recommended Management Timing map above). Mowing milkweed mid-summer in areas where there is a lull in monarch activity, such as the Southern Great Plains, may promote milkweed growth and late summer or early fall breeding (Baum and Mueller 2015; Fischer et al. 2015). Always survey for monarchs before conducting mid-season mowing.
- Mow after native plants finish blooming and dispersing seed.
- Mow once or twice per year. Consider mowing within an integrated vegetation management framework on just the areas of heaviest weed infestation. Mowing too frequently disrupts growth and the ability of flowering plants to compete with grass. During the first year of some restoration projects (e.g., prairies), more frequent mowing may help with weed control. Many DOTs have adopted deferred mowing programs to benefit monarchs and other species.
- See Okies for Monarchs’ “Best Management Practices for the Monarch Butterfly in Oklahoma Rights-of-Way”.
- Use a minimum cutting height of 10-12 inches (shorter may be needed for early establishment
mowing). This effectively removes seed producing parts of most invasive plants and minimizes wildlife impact.
- Use a flushing bar and cut at reduced speeds to allow wildlife to escape prior to mowing.
- See Okies for Monarchs’ “Best Practices for the Monarch Butterfly in Oklahoma’s Rangelands”
See Monarch Joint Venture’s handout titled “Mowing: Best Practices for Monarchs” for additional information including regional time frames during which management activities may be less detrimental to local monarch populations. While the document is targeted for mowing best practices, the timing windows are applicable across different management techniques as well.