Japanese knotweed- overhyped?

daveyjp

MrsFingersCrossed wrote: »

Can of worms! I've read it doesn't spread by seed too but it seems too much of a coincidence that we'd viewed a house where it's in the vicinity (with a maintenance plan in place) and just weeks later new shoots appeared on our doorstep. We'd recently filled in the property questions form (for our buyer) saying none on the premises or in the vicinity, so horrified to discover said suspicious weed in gravel. We're reassuring ourselves the statement is still true because we pulled up tiny shoots and incinerated them, hence no JK on premises, still. But a shock nonetheless.

The rhizome system grows underground and if the winter is mild it will do so between October and March. I was asked to go and look at an outbreak a few weeks ago, the new very substantial shoots were just starting to appear from the old crowns, in addition there were very spindly new growth shoots 3-5m from the main outbreak.

If left these plants will develop into new crowns and what was an outbreak a metre or so across becomes 3-5m across in a very short period of time. Thats when it gets expensive to remove.

moneyistooshorttomention

I've checked out those photos of crowns and will know how to identify that particular aspect now.

One question about those crowns being = Are they always above ground or could they ever be lurking out of sight beneath the soil surface?

daveyjp

The main crown will be just below, the rhizomes can be metres deep and these will develop into crowns.

You are better leaving the plant at this time of year and applying glyphosate to the leaves at the end of summer. The weedkiller will then reach the rhizome network and the plant will die off.

I see vast outbreaks on my regular train journeys and in the last month the plants have gone from nothing to about a metre high.

Gingernutty

My neighbour has small crowds of stems busting through concrete that's a good 5 inches thick.

The crown will be below the concrete.

Hoploz

Have been round my land this weekend checking for it! No sign I'm glad to say. Bought last autumn, the question on the sellers form about presence of JK was one of several that were left unanswered. I hadn't really thought much about it till I read this and did a bit of research!