The Season Of Vigilance: Noxious Invasives, Introduced Weeds And You

-Olivia Wylie, Master Gardener Denver

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The saying goes ‘a weed is a flower whose virtue hasn’t been found yet.’
But you have to wonder with some of the weeds in the garden. What exactly, you think as you sweat and tug, is the virtue of bindweed’s strangling grip on other plants and your garden? What’s the virtue, you think with nervous venom as you pull on your gloves, of a spurge that can give you blisters, kill your dog, and is invasive?!

Unfortunately, the virtues of these plants are exactly what makes them weeds. Adaptability. Tenacity. Ability to survive harsh conditions. It sounds like a compliment when you’re reading a garden catalog, but with the wrong plant in the wrong place, it’s a recipe for disaster on a garden-wide, city-wide or even state-wide level.

Sadly this disaster has played out many times, and today we carry the burden of our forbears’ horticultural mistakes across the country. To combat this issue, a Federal Noxious Weed act was passed in 1974, and our own Colorado Noxious Weed Act was passed in 1996. The Act supports the creation of programs to combat the invaders, and the Department of Agriculture maintains a list of plants to look out for called the Colorado Noxious Weed List.

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This list is invaluable as a resource, and is broken down into several sections. Quoting from the Colorado Department Of Agriculture,

List A Species in Colorado are designated by the Commissioner for eradication.

List B Species are species for which the Commissioner, in consultation with the state noxious weed advisory committee, local governments, and other interested parties, develops and implements state noxious weed management plans designed to stop the continued spread of these species.

List C Species are species for which the Commissioner, in consultation with the state noxious weed advisory committee, local governments, and other interested parties, will develop and implement state noxious weed management plans designed to support the efforts of local governing bodies to facilitate more effective integrated weed management on private and public lands. The goal of such plans will not be to stop the continued spread of these species but to provide additional education, research, and biological control resources to jurisdictions that choose to require management of List C species.

Watch List Species that have been determined to pose a potential threat to the agricultural productivity and environmental values of the lands of the state. The Watch List is intended to serve advisory and educational purposes only. Its purpose is to encourage the identification and reporting of these species to the Commissioner in order to facilitate the collection of information to assist the Commissioner in determining which species should be designated as noxious weeds.’

But we all know what happens when we leave the work up to the government and sit on our laurels. It’s up to every gardening citizen to know your noxious invasives, your invasives, your introduced weeds and what to do about them!

Know Thy Enemy

We could spend entire articles on the exact definition of invasive species, and in fact a wonderful white paper on the subject can be found at this link. But here’s the skinny.

niNoxious Invasive- the long winded definition is quoted from the 1974 Act, and runs ‘Noxious Weed means any living stage, such as seeds and reproductive parts, of any parasitic or other plant of a kind, which is of foreign origin, is new to or not widely prevalent in the United States, and can directly or indirectly injure crops, other useful plants, livestock, or poultry or other interests of agriculture, including irrigation, or navigation, or the fish or wildlife resources of the United States or the public health.’

Put plainly, not only will Noxious Invasives make you livid, they can make you sick. These are the true thugs of the plant world. Generally these beasts will be found on the Commissioner’s A list. These include vile things like Myrtle Spurge/ Donkey Tail Spurge, Euphorbia myrsinites. Originally introduced as a ‘lovely and tenacious rock garden addition’ (a direct quote from an old seed catalog, the company shall remain unnamed!)  it was indeed tenacious. TOO tenacious. And if you decide to pull the stuff, it retaliates with sap that causes painful blisters. Get it in your eyes? You’re taking a trip to the ER my friend. Dogs that encounter the sap can actually die. Not such a great addition after all, and if you see it in your garden it needs to be eradicated by (almost!) any means necessary. Before you tackle it, PLEASE pull on goggles, a long sleeve shirt and pesticide-grade gloves. In fact, I prefer to pull on a thin pair of fabric gloves and my nitrile pesticide gauntlets go on over those. You can never have too much protection.

dtInvasive Species-  an invasive species is best defined as a non-native plant that could cause harm to the native ecosystem by competition pressure. When you pull prickly lettuce before it smothers your lovely little columbines, that’s a perfect example. These plants are tougher, more prolific, easier spreading or in some way advantaged over other plants, and if allowed will run roughshod over our native flora.
Dalmatian Toadflax is the classic example. I’ve taken out of town friends on a drive through the foothills and heard them exclaim ‘oh look at that yellow field!’ I look over and give a heartfelt groan, because I know that field has nothing living in it save a single invading species that has choked out native plant life.

isIntroduced Species-Where list A Noxious Invasives could be compared to a plant felony, plants that fit the Introduced Species are more of a misdemeanor: they’re trouble, but not ecological disaster. Defined as ‘an organism that is not native to the place or area and has been accidentally or deliberately transported to the new location by human activity’ in the 1974 Act, they’re your neighbor’s old mint bush sending shoots into your yard. In my Capitol Hill neighborhood, the quintessential example is the Cap Hill Weed (no not THAT weed),Campanula rapunculoides or Creeping Bellflower. Local lore says it was introduced in the 1920s to grace the great old mansions that once stood in their majesty along these streets, and it’s been with us ever since. It wanders from garden to garden in the older parts of town, sneaking under trees and into small areas, worming into bare spots in the grass and gaining a foothold most anywhere. Some people have simply accepted it as a garden plant like their grandmothers did, but most of us fight it tooth and nail because we’d like to have a garden with more than one plant in it!

Fighting The Good Fight

Delving into reclamation and eradication tactics for species that are toxic, invasive or introduced pests is a paper in itself, and many have been written. The Colorado Noxious Weed Species List has details on the treatment of every species it lists. But here’s some general tips.

  • Safety First. Wear gloves, wear long sleeves, wear safety glasses or goggles if you run any risk of getting poked in the eye or sprayed with sap
  • Get The Root!  Pulling does little good if there’s a root stocked with nutrients ready to shoot up new leaves under there. If you use pesticides, make sure your choice specifies ‘kills the root’.
  • Tenacity Is A Virtue. Don’t get discouraged if the plants come back again and again. keep using your favorite eradication method, and you can wear these invaders out!

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One response to “The Season Of Vigilance: Noxious Invasives, Introduced Weeds And You

  1. Excellent article, thanks!

    Liked by 1 person