Invasive species cause headaches for area parks
HOMER LAKE – Autumn olive is a good thing to plant if you want to fix nutrients in your soil. But, as often is the case with good things, you can quickly get too much of autumn olive.
Once you've had autumn olive pointed out to you at the Salt Fork River Forest Preserve near Homer, you'll see it everywhere. Before Homer Lake was a park, it was a state tree nursery, and state officials encouraged planting it between rows to fix nitrogen in the soil.
Decades later, it is the "monster invasive species" at Homer Lake, according to Natural Resources Director Dan Olson of the Champaign County Forest Preserve District.
Each of the forest preserves has its monster. At the new River Bend, it's two types of honeysuckle. At Lake of the Woods, it's the Bradford pear. At Middlefork, the cleanest site, it's garlic mustard.
A similar situation exists at two Urbana parks, Busey Woods and Meadowbrook Park.
Derek Liebert, Urbana's natural areas coordinator, said bush honeysuckle, vine honeysuckle, sweet clover and garlic mustard have been rooted out by volunteers at Busey Woods.
For a 50-acre remnant like Busey Woods, a strong group of volunteers can make a difference, but the park district has also used a grant to bring in heavy forestry mowers in the south end of Busey Woods.
There's little bit of autumn olive at Busey Woods, Liebert said, and more of it at Meadowbrook Park.
Autumn olive may be ornamental, like multiflora roses, and garlic mustard may be delicious, but they're not native to central Illinois, and, like kudzu in the south, they adapt all too well, crowding out native species that get along better with the flora and fauna of the flatlands.
Autumn olive, a native of east Asia, can grow up to 20 feet high. It loves poor soil, blocks the sunlight from the other species and resists burning. It takes a chain saw, or the hiring of a forestry mower crew, to rip it from the earth, and then its stumps must be poisoned.
Olson was spending a perfect August morning near the site of Homer Lake's recently announced wetlands meadow.
An indigo bunting – a native bird – flashes blue against the sky. Ironweed, another native, gives color among the grasses and Queen Anne's lace. He makes a mental note to remove a Canadian thistle, another invasive species.
To his left stood a wall of autumn olive. The leaves are, well, olive-colored on the top side, silver-scaled on the bottoms. Some of the shrubs show red berries, giving away the plant's over-fecundity.
"It's still sold in some (garden) stores, which is crazy, if you ask me," Olson says.
On a trail, the olive plants crowd in from either side. They have filled in some trail sections, requiring a chain saw remedy, since branches can grow 6 feet a year.
"Along with all the other bad things about autumn olive, it detracts from the aesthetic beauty of the trail," Olson says.
Only a gray dogwood "gives it a run for the money" in reproducing and taking over the section; autumn olives, Olson says, put out hundreds of thousands of seeds a year.
On the west side of the forest preserve, a stand of autumn olives has been attacked by forestry mowers. A few desirable species, oak and ash and hickey, have survived, and pin oaks run in rows.
Near Collins Pond, Olson points to the remains of another chopped-down stand. Autumn olives attempted to emerge from the stumps, but chemicals cut them off.