by Andrea Williams
Very often when I talk to people about invasive plants, I hear, “It’s all green, isn’t it?” Yes, almost all plants are green—and all vertebrates exhale CO2. There is an even greater diversity of life within the plant kingdom than the animal, but we seem to appreciate it less (although even I will admit to being more excited seeing a mountain lion than a California nutmeg). Would we accept a world in which roof rats, wild pigs, and pigeons were the only wildlife we saw? But very often we shrug when faced with a solid stand of invasive non-native plants, which have little to no value as habitat or food, and not much in the way of landscape interest.
Gardeners and landscapers create interest by using plants that vary in structure and color. They also look for plants that are hardy with few pests and diseases, grow quickly, and have a profusion of attractive flowers or fruits. Unfortunately, these are also characteristics of an ideal weed, and several of the invasive plants we are troubled with today originated in horticulture. I tend to think of garden plants in terms of a “change your mind” factor: if I planted this now, and then changed my mind about it, how hard would it be to remove? If the answer is anything other than “not hard”—if it spreads by roots or stems that are difficult to pull, if it seeds aggressively, if it won’t stay where I planted it—I prefer to avoid it, as I know these plants are weeds. If they’re not weeds in my yard, they’re weeds to someone nearby, and just like I don’t want dogs squatting in my yard, I don’t want cotoneaster popping up either.
When gardens scale up into landscapes, it makes me think of kitchens. Landscapes tend to follow similar design fads, with plants coming in and going out of vogue as people change their minds about what looks good. When I see sweet alyssum I think avocado and gold appliances; when I see Mexican daisy I think granite countertops and maple cabinets. And I, for one, can’t wait for the daisy fad to pass, since it’s spreading onto MMWD lands and beginning to displace native species.
In the interest of protecting our limited water supply and ensuring the efficient delivery of landscape water, MMWD developed and adopted Water Conservation Ordinance 414, which requires certain things to be considered when designing and installing landscaping. One of these requirements is not planting species known to be weeds. To that end, MMWD has put together a handy list of plants not to plant, with alternatives for species still in use despite a high degree of difficulty in the “change your mind” department. Some species are still allowed, even though we know their weedy ways—there isn’t a turf grass out there that isn’t invasive—but by doing a few simple things you can reduce the risk to wild areas. Aside from “spaying and neutering” your plants by removing fruits of wind- or bird-dispersed plants like English ivy and cotoneaster, you can dump your yard waste in your own compost pile or green bin, and NEVER off the side of the road! People who would never dump an old avocado green refrigerator in wild lands might think nothing of tossing green waste over the side, because “It’s all green, isn’t it?” But unlike the fridge, that green can spread, as it has off the side of Bolinas-Fairfax Road where someone dumped cape ivy and periwinkle. And that’s trash that multiplies on its own!
By changing our minds a little—valuing native plant diversity, planting species with an eye to potential problem plants, and disposing of green waste responsibly—we can have (or prevent) a huge impact on the places we love.