Sunday, August 14, 2011

Japanese Knotweed - Invasive Species

So...the saga of the backyard septic installation continues.  We were happy to see our grass growing in the new backyard fill, even though there was also a prevalence of weeds.  There was one plant that I had never seen before, which I hoped was some sort of nice bush I could use in my landscaping.  It sprouts with a reddish tinge, grows quickly, and has broad oval pointed leaves.
 Unfortunately, as a visiting friend warned us, this plant is Japanese knotweed, which is highly invasive.  Apparently there was a landslide where various contractors were getting fill dirt from, but was from a location highly infested with knotweed - a highly aggressive invasive species.  So, my options are now to use poisonous chemicals, cover with heavy black plastic for a number of YEARS, or cover with 5 FEET of new clean soil.  Pulling up from the roots can actually spread it worse, since root systems can be 45 feet long, and only a small root fragment can restart a colony.  Another option is to cut it down up to 6 times a season for 5 years or more, which is sometimes used for large stands of it, but it can regrow to full size within a month or two.
 I asked the Kodiak Water and Soil Conservation District to come and look at it, and they suggested they could target spray it with something, and only kill a little grass since the knotweed are not yet well established.  It might or might not fully address the problem.  What a pain!

1 comment:

Zoya, Patrick, Nora and Stuart said...

I'd kill it now! That stuff is bad and looks ugly in the spring. Go check out the places it is growing now (like above the stoplight on the hillside - and I think there is another patch need Cost Savers) and you will know the future unless you act now! Also I can't believe that contractors are spreading that kind of fill around town!

My invasive problem is hawkweed - and it is already hopeless. I just try and keep it from blooming. Patrick