Over that past few years, I have had several opportunities to do a bit of research on listings on the Colorado Noxious Weed List. (See http://www.colorado.gov/cs/Satellite/Agriculture-Main/CDAG/1174084048733)

Plants on the list are introduced to our area by a variety of methods. Some plants escape cultivation (like wild caraway). Others come in as volunteers in pots of other plants being sold at big box garden centers. And some…well some we have bought at the garden center and voluntarily planted them in our gardens in the past!

It is interesting how many of the plants listed got their start in our area as introductions for gardens (They are called “escaped ornamentals”). They were sold in garden centers and nurseries for our gardens before we realized how invasive they were. This would explain the protest of “But it is so pretty!” I get when I tell someone that a plant is on the noxious weed list. Sure, it’s pretty – that’s why people bought it for their gardens years ago.

Escaped Ornamentals Currently on the Colorado Noxious Weed List

A few examples of current members of the noxious weed list that started as offerings for our gardens (but are now illegal to sell) include the following:
bouncingbet (Saponaria officinalis)
myrtle spurge (Euphorbia myrsinites)
purple loosestrife (Lythrum salicaria)
common tansy (Tanacetum vulgare)
dames rocket (Hesperis matronalis)
moth mullein (Verbascum blattaria)
oxeye daisy (Chrysanthemum leucanthemum)
Russian olive (Elaegnus angustifolia)
yellow toadflax – also known as butter & eggs (Linaria vulgaris)

Pretty amazing, isn’t it?

Candidates for “Noxious Weeds of Tomorrow”


Nasella tenuissima

So this has me constantly thinking about what we may be planting now that are the (trumpet fanfare) Colorado Noxious Weeds of Tomorrow! I have no doubt that some of our current garden center buys will be on the list years from now, it’s just a question of which ones and how far they’ll spread before they warrant being listed.

Some of the possible candidates in my head include the following:

Mexican feather grass (Nasella tenuissima) – Have you ever seen how invasive some ornamental grasses (like some Miscanthus species) are in other areas of the country? Well, this beautiful little grass definitely shows some invasive tendencies. I love the way it looks in my garden, but each year, my feelings that it should probably be eradicate from my garden grow stronger. (The picture above shows a group at the local xeriscape garden in winter. “But they’re beautiful!” you probably protest, right?)

Mountain bachelor button (Centaurea montana) – This really has a beautiful flower! We’ve been trying to eradicate it from the utility company’s xeriscape demonstration garden where I volunteer for years. Some people report growing it with no invasiveness, but further investigation reveals that they deadhead it diligently and pull up any unwanted seedlings. So…it sounds like it still definitely wants to be invasive, but some people are willing to put extra time into maintenance to keep it manageable (and which of us gardeners doesn’t have a pet invasive plant they’re willing to spend extra time taming?).

Catmint (Nepeta mussini) – I bought this little beauty home as a freebie from the garden where I volunteer. After four years, I had it coming up in the cracks in my pavers, in the cracks of the sidewalk, all over my garden beds, and even one under the windshield wiper of the car! That was the last straw. For the past four years I’ve been eradicating it from my landscape. Now not ALL catmints are invasive, but many agree this particular species is very invasive. (Garden catalogs describe it as “reseeding vigorously.) Since I like the look of the plant, I’ve replaced it with Nepeta faasenii ‘Walker’s Low.’

So what about you? Any nominations for the “Noxious Weeds of Tomorrow” list?