A good preliminary practice before you start any landscape design, is to find the latest list of invasive species for the area in which your project is located. Some of the plants catalogued on the lists are favorites that might surprise you. They have spread to the point of being a nuisance to the local native ecosystems. The lists change. Something that may have seemed the hot nursery plant a few years ago, has now lost its popularity and become more of a rude, uninvited visitor. Because you understand how important it is to use vigorous, un-daunted plants for challenging situations like roadsides, you may be considering one of these thugs, without realizing it has turned pushy and ill-mannered. Cogon Grass, also known as Imperial Blood Grass, was considered quite stunning in gardens over a decade ago, but has become a monstrous and scary threat to roadside plantings in the Southeast. It can take out a Pine forest with its Borg-like root system. Avoid using any of these invasive plants (or their close relatives) in your landscape designs, especially on roadsides. Our vehicle corridors act as a catalyst for spreading these plants, and keeping them in check is very costly to taxpayers! You can browse a lot of the lists, both in the United States and internationally, at the United States Department of Agriculture Library and Invasive Species Information Center.
You may see some familiar faces in the invasive species lists. Heirloom shrubs and picturesque vines turn up at times. You’re not a bad person for liking some of the plants on the list. They may evoke fond memories. I don’t think you need to go out and torch any of the category-one list makers in your own yard, even though you might feel like it sometimes! But,for the seed distribution corridors that are our roadsides, more caution is advisable. Stay away from the offenders.
By the way, torching Cogon Grass will not eliminate it! Sometimes the rhizomes (root mat) can grow 5 inches deep, so it will re-sprout from the scorched tips. A lot of the broad-spectrum herbicides are ineffective without repeated doses, timed just right. Maintenance equipment that has worked in invaded areas has to be disinfected to remove the highly-viable seeds that drift through the air in the spring. It is the Ebola of the plant world.
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.
Don’t be too frightened of invasive species. They can be conquered if eradication is given priority status. As a designer, you need to know what not to plant, but you also need to know which of these bad guys has already become established on your site, and put measures into place to get rid of them before investing precious money and time on bringing about your newly-designed landscape transformation. Always include this important consideration as you begin your projects.