When Aliens Attack!

Saint John is under attack and most of its citizens are blithely unaware!  We have many aliens living in our lawn and invading our garden. Fortunately, most of them are not more than an aggravation.

I mean stop and think, lawn lover; what it would have been like if our pioneer ancestors had stomped out the dandelion when they realized it was escaping from their vegetable garden?  Or if Shakespeare had never mentioned the grape-stealing Starling, so it was never released into Central Park?

These things aren't true so we gardeners must soldier on.

Unfortunately, some invaders are not so benign. A strangling plague of Japanese Knotweed (or Mexican Bamboo as it is also known) can kill trees, and pretty old-fashioned Dames Rockets out-compete important natives like milkweed and goldenrod.  The "Valley" as seen from the highway is a gallery of these plants. Well, it is until the mortal combat taking place ends and all that is left is Polygonum cuspidatum.  It is this knotweed that is the arch-villain of this post.


Polygonum cuspidatum (or its aliases Fallopia japonica, Japanese Knotweed, Mexican Bamboo, and Fleeceflower)

Jeff Hallworth, P. Ag., Coastal Invasive Plant Specialist for the BC Ministry of Forests and Range, noted that, "Knotweed is considered by most experts to be amongst the world's worst invasive alien plants and one of the most difficult of all plants to eradicate." The Comex Valley Echo via Canada.com

How do we get rid of it? It seems the best bet is to keep it bush-hogged to the ground and never letting it get tall enough to flower. This will help deplete its energy. Tilling does not seemed to be recommended as it can spread from a small piece of root. So tilling can spread it.

In the Spring, or once it is hacked back, cover the patch with tarps:

Begin by investing in some plastic or poly tarps, with which you'll cover your patch of Polygonum cuspidatum and smother it. Invest the money in the biggest tarps you can find -- the investment will save you a lot of labor (see below). If the landscape area from which the Japanese knotweed emerges is covered in the early spring with tarps, Japanese knotweed's growth is immediately impeded.  By David Beaulieu, About.com Guide

The above article also recommends keeping it cut to the ground as a part of a three-pronged approach that includes injections of herbicides such as Round-up. As a sustainable gardener, this last suggestion is not something I can personally recommend.  According to the No Kidding article from Comex, the UK spent over a billion pounds using pesticides to try to eradicate it. So chemicals alone are not the answer anyway.

So, if it's so horrible how did it get here? This quote from the DAISIE pamphlet on Fallopia japonica gives a clue.

Fallopia japonica and F. sachalinensis were introduced into Europe as garden ornamentals in the 19th century and soon escaped from cultivation. Because of its showy blossoms, F. japonica became a popular plant in Victorian gardens of Europe, winning a gold medal in 1847 from the Society of Agriculture and Horticulture at Utrecht as the most “interesting” plant of the year.

Other noxious weeds thrive here in the city. Some of which compared to Japanese Knotweed may only seem more than scabby minions to its criminal master mind, but they should not be underestimated. Dames Rockets (Hesperis matronalis), Goutweed (Aegopodium podagraria L.), Rosa multiflora, White Popular (Populas alba), Sea Spray Rose (Rosa rugosa), Common Lilac (Syringa vulgaris) are all alien invaders taking a toll on our city.  We are not immune just because we are in the north .  Our mild winters and summers make for a wonderful pleasant home for these invaders.

So don't buy them, don't propagate them, make sure you properly identify them before destroying them; as most resemble an innocent native species, such as Northeastern Rose (Rosa nitida). Then dispose of any remains in the city compost.

In the future make sure when you buy that pretty Lilac that it is a non-suckering hybrid. Try a hardy rose based on a native species, like Metis (available at Cornhill Nurseries) which is a Rosa nitida cross. If you are not sure then buy your plants from a garden centre that employs or is owned by a professional horticulturalist and have them point you to the alternatives.

Here is a Flickr photo essay on the invasive weeds found here at Seaside Park. It's good to know your enemy.