Knotweeds ~ not all bad

Knotweed is a word that can strike fear into the hearts of many a gardener, homeowner, property developer or frankly anybody who has been unfortunate enough to suffer at the roots of Fallopia japonica, more commonly known as Japanese knotweed. This plant has earned its fearsome reputation through years of insidious growth smothering the gardens of unsuspecting people, ripping up the foundations of their homes and costing millions of pounds each year in the UK alone.

There are however many different types of knotweed, none quite as infamous as Japanese knotweed but many far less fearsome and even pleasant. American bistort for example grows from under 30cm to 1.5m high and looks like a white flowered grass. Like Japanese knotweed it has edible parts to it, however rather than the fresh stems, in American bistort, it’s the roots which are edible, either raw or roasted resembling the flavour of roast chestnuts.

Another interesting knotweed species is the water smartweed, a variation which grows in water looking similar to a lily. The water smartweed also has some edible qualities, though the best bit of that plant is the stems again like Japanese knotweed.

Of course there are the plants in the knotweed family which share the same invasive qualities as knotweed itself does; common knotweed for example, is one that likes to sprout up where it’s unwanted. However, it’s somewhat easier to get rid of than Japanese knotweed removal is, simply pulling it up is fairly effective, especially if you catch it before it produces seeds and failing that it can be stopped with herbicides or covering it over with landscaping fabric and mulch; a far cry from its sibling which punches through building foundations, tarps, tarmac and all manner of structures.

Of course if you do find anything resembling knotweed in your garden, it would be a good idea to check and double check which type of knotweed it is, if it’s the dreaded Japanese knotweed, time can be a big factor, the longer it’s left, the more ground it will cover, whether you can see it or not; the roots can spread several meters out and around any visible stems, so you need to really nip them in the bud. Where possible the best approach is likely to use a herbicide either injected into the stems or sprayed over the leaves. Picking the stems while they are very young can be an effective means of slowing it down, however you need to be very careful of what you do with them, since even small parts of the plant can regrow, and it’s a crime in the UK to cause knotweed to spread. But of course, if in doubt, ask an expert!