By Alex Hearing, Conservation and Parks Manager, Great Parks of Hamilton County

Over the last year, guests of Miami Whitewater Forest, Mitchell Memorial Forest and Shawnee Lookout may have noticed some rather naked-looking fields. You may have even thought to yourself, “Wasn’t there a prairie there?” or “Wow! Looks like a tornado demolished this forest!”

Don’t worry – these fields represent Great Parks of Hamilton County’s varied approach to invasive species management and removal based on the needs of the habitat. In this post I will highlight some of the techniques and equipment we use to stand out as leaders in conservation, preserving biodiversity in Southwest Ohio.

On our Conservation & Parks team, we spend a lot of time planning and deliberating our approach to invasive treatment among the wide variety of habitats we manage. “Sometimes it takes a sledgehammer, sometimes it takes a scalpel,” is a phrase we use to describe the needs of each site.

The Sledgehammer

The sledgehammer we’re referring to is a piece of equipment known as a “forestry mulcher.” This is a mulching unit that attaches to various mechanized equipment, spinning at 2,000 rotations per minute. We use it as an invasive-pulverizing machine.

This technique is used like a reset button in areas so inundated with Callery Pear, Bush Honeysuckle, or other woody invasives, that more delicate strategies would not be practical for the task. The mulcher can also be used in sites that may have wildlife sensitive to herbicides, such as wetlands, vernal pools (small, often temporary ponds that amphibians often use for spawning), and riparian areas (forested habitat along streambanks).

After the forestry mulcher clears the site, Conservation & Parks technicians follow up by cutting any remaining stumps or treating remaining invasive species with selective herbicides to minimize the impact on native vegetation. We pay particular attention to invasive woody plants by treating them with a high concentration “stump spray” to prevent resprouts and make follow-up treatments easier. The team also removes large debris and mulch piles that could potentially impact the growth of native plants and seasonal ephemerals.

Some sites managed as grasslands or prairies can be further enhanced with the use of prescribed fire (Rx Fire) after the mulching and regrowth. Rx Fire has many benefits, which could be a whole blog post itself. Some of the benefits include the removal of biomass (dead plant debris), allowing for more robust plant growth and propagation, reintroduction of nitrates to the soil, and keeping new woody plant growth at bay. Native habitats benefit and have evolved to exist with seasonal fires.

The Scalpel

Depending on the site, an almost surgical approach can be used. These techniques can be as simple as mindful mowing, or mowing done only once or twice a year during the time when critters aren’t using the area as much and when it benefits the native plants most. The small grasslands where we would use this approach are areas that we mowed more frequently in the past for picnic areas or ballfields but weren’t being used much by park guests anymore. From a sustainability perspective, mindful mowing allows Great Parks of Hamilton County to save on the use of fossil fuels and reduces work hours that would be needed to mow the park weekly, freeing us up to focus on projects like native tree plantings and habitat development. Reduced mowing also maintains food and shelter for wildlife and pollinators in an under-utilized space.

Appropriately timed mowing contributes to invasive species management by reducing the spread of annual or biannual invasive plants (such as thistles, teasels, and invasive grasses like Japanese Stiltgrass). It’s all about timing though, and some research is required for the mowing to happen right before the plant is expected to go to seed so that it will not have the energy to regrow seeds before the end of the expected growing season. Consistent follow-up is important, as many annual invasive plants can have dormant seed banks lasting over five years.

In some situations, our strategy calls for the use of herbicides. Herbicides, when used properly and selectively, allow for Great Parks staff to manage natural areas across a wider range to promote biodiversity, helping native species thrive. Whether they are green and leafy, flying and buggy, furry or slimy, the landscape and critters that depend on this strategy would look much less diverse and vibrant without this vital tool in our belt.

As mentioned before, one of our most used techniques for invasive treatment, and something that almost anyone can do in their backyard, is the cut-stump-spray method. This method is easy and affordable for most people and can help even in your own backyard. For this approach, woody invasives such as Bush Honeysuckle are cut to about 1-2” from the ground and treated with a 25-33 percent concentration of glyphosate. This mixture is about a 2:1 water-to-herbicide mix from concentrated glyphosate sold at most garden centers. The mixture can be applied by a handheld spray bottle, backpack sprayer, or even dabbing onto the stump with a paintbrush or “wick” (pretty much a sponge on a stick). The herbicide is carried by the exposed sapwood to the root system, killing it and preventing stump sprouts and regrowth. This method minimizes over-spray and is very effective in only managing the targeted species.

Finally, we employ foliar spraying (spraying the leaves) and basal-bark treatment using a range of herbicides that can be very specific to the species of the invasive plant, or, a broader range of chemicals to target a host of species. Generally, herbicides can be split into several groups: broadleaf selective, grass selective, and non-selective. Within those groups, certain chemicals are even more selective and can be used to reduce collateral damage and reduce the risk of over-spraying and harming pollinators. For instance, broadleaf-selective clopyralids can be used to target teasels and thistles with minimal impact on Milkweed (an important pollinator plant). Basal-bark treatment uses oil-based herbicides that soak into the bark around the base of hardier invasive trees like Tree of Heaven and Callery Pear. The tree will then die and can be removed the following season or left standing for wildlife habitat.

Certain non-selective herbicides, when used at the right time, can target invasives with minimal collateral to native species (such as fall Honeysuckle treatment, or winter Creeper treatment on warmer days in the winter). The tools used in herbicide treatment range from spray bottles and backpack sprayers to high-capacity sprayers used for larger-scale treatments.

Precautions are taken with all herbicides to reduce environmental impacts. Most of the herbicides we use are considered safe for pollinators, but as an extra measure, spraying is typically done earlier in the day when insects are least active. During the hottest days in the summer, we limit the use of mechanized gas equipment for both the safety of our staff and the air quality of the community. Chemicals are not used in the rain, so we can reduce runoff and prevent waste. Herbicides are not effective if they don’t have time to absorb into the leaves.

Putting These Management Tools into Action

Staff at Miami Whitewater Forest recently used a forestry mulcher to “reset” several overgrown sites throughout the park. The largest was property north of the hike/bike trail along Dry Fork Creek in Crosby Township. The site was cleared in winter 2022-23 and has improved dramatically with the regrowth of native species over the summer growing season, which also allowed us to ease our follow-up treatments.

This winter we mulched at Mitchell Memorial Forest on the hillside prairie across from mountain bike loop A, and at Shawnee Lookout in the prairie behind the Pioneer Cabin.

Running Buffalo Clover (RBC), once endangered in Ohio, has thrived at Shawnee Lookout and Miami Whitewater Forest thanks to mowing timed to reduce competition. RBC also benefits from soil disturbance in spreading its runs, or vine-like growth, from the central plant. Historically, grazing of plants and stomping of hooves by woodland bison would have helped to spread this plant, hence the name “running buffalo clover.” In a sense, we’re just riding around on mechanical buffaloes spreading biodiversity!

With a combination of timed mowing, grass-selective herbicides, and enthusiastic volunteers to hand-pull plants, Mitchell Memorial Forest has managed over 27 acres of Japanese Stiltgrass over the summer.

At Embshoff Woods Nature Preserve in Delhi Township, Great Parks Conservation & Parks crews have been hard at work at invasive species removal by clearing Amur Honeysuckle and Asiatic Bittersweet. Although the forestry mulcher was not used, park guests may notice large patches of cleared area using the cut-stump spray method near the park entrance. The crew also used basal-bark treatment on Tree of Heaven (Ailanthus) throughout natural areas in the park.

Invasive species treatment is a year-round job. These accomplishments are just some examples of our continual efforts to provide safe, enjoyable spaces for people to experience native ecosystems and homes for wildlife to flourish. More information on our restoration and natural resources management is available at the Restoration and Management page on greatparks.org.