Seeding Native Mixes
Before invasive plants spread to the point from nuisance to menace on our roadside landscapes, they were used to stabilize soil in very difficult situations. Weeping Love Grass, Lespedeza, Crown Vetch, and Kudzu were used to quickly hold the 2:1 slopes adjacent to bridges and areas with limited space for gentle grading. The dust bowl was still fresh in everyone’s mind. How bad could things get compared to that, right?
In the seventies the rapid dominance and persistent seed bank of these vigorous ground covers started being noticed as a problem. Transportation agencies began fighting back in the past couple of decades to combat the damage of the spread of invasive species. But, at the same time, people who had experienced the wildly successful establishment of these plants continued to use them. Some information sources continue to this day to list them as recommended species for erosion control.
Contractors push back when new regulations against fast and cheap ground covers are proposed. Native species mixes don’t perform as well as the old-time erosion control favorites, especially on difficult roadside situations. Native seeds are more expensive and harder to find in the trade. They take longer to germinate, and erosion control regulations often call for establishment in just a few days. It is difficult to argue for more expensive native seed.
Those that love the way things have always been done tend to look at native grasses as weeds. Farmers have fought them in agricultural situations. Broomsedge has a particularly bad reputation as an indicator plant for bad farming and poor soil conditions. The mindset against non-pasture crops is very strong.
You can find more information about trees in The Advanced Guide to Roadside Design: How to Create Successful Public Landscape Projects, part of The Advanced Guide series.
The way to change attitudes is to demonstrate reliable success and profitability using native species mixes. Seeding is relatively inexpensive, regardless of species, so the cost difference between invasive seeds and native seeds is negligible. Going native will not break the budget of your construction project, and can save big bucks for long-term maintenance costs. Natives naturally grow well in local soil conditions, so establishment happens easily. Native seeded species require much less babysitting to keep them within bounds. The cost to control invasive plants can run into the millions in some states. If you are designing vegetative seeding for erosion control:
• Be specific about the rate per acre and species choices you allow on your projects.
• Insist on double or triple rates of seeding on steeper slopes for more reliable establishment.
• Mix a native millet species in the seed mix for immediate cover, until the late bloomers start germinating.
• Include both cool and warm season species in your mix, since planting may not take place at the perfect time of year.
• Advertise that your firm or company uses native seed mixes, rather than old-timey invasive monocultures. Be proud of choosing erosion control methods wisely.
• Take pictures of successful native plots on difficult slopes to reassure skeptics your native mix will work.
• Point out the added maintenance cost of controlling invasive plant populations that shade out native competition, including costs to prevent invasives from toppling trees, breaking through pavement, and obscuring traffic signs—very dangerous!
• Let stakeholders know that invasive plants are dangerous and expensive—not just nuisances. Native mixes reduce costly labor and recurrent maintenance burdens.
Sell the idea of using native plants for erosion control to your clients. These mixes are quiet and well-behaved compared to their rude, bullying invasive competition. Using native mixes makes good economic sense.