This plant is taking over my flower bed.

(Question)

I started to notice the plant (picture attached) a year or so ago.  What I didn’t realize was how invasive it was becoming.  It is now entwined in my irises and spreading.  It is very difficult to pull out as there are so many shoots that are leading to many new plants.  It reminds me of shoots under the surface like grass or goutweed.  I would welcome any thoughts on how to deal with this invasion.

(Answer)

Finding plants that have become invasive in one’s garden is a cause for concern and dealing with them requires vigilance.  The attached photo certainly illustrates the problem with your irises, but makes it challenging to definitively identify the invasive plant.

It could be Vincetoxicum rossicum, commonly called dog-strangling vine.  This is a very aggressive vine that wraps itself around anything in sight, grows at least one to two meters and forms dense mats of vines.  It has become very prevalent in Ontario over the past few years and is quite a nusience to the home gardener and farmer alike.  If you are not familiar with it, the link below will bring you to a site which will give you information in order to identify and control it.

https://www.invadingspecies.com/invaders/plants-terrestrial/dog-strangling-vine/

Saponaria officinalis, also known as Bouncing Bet or Soapwort, is another possibility.  This perennial plant also spreads by a rhizomatous root system and has opposite leaves at each node along the stem.  Each leaf has three prominent veins that run from the base.  The fragrant clustered flowers that it produces in mid-late summer are usually pink.

The key to controlling invasive plants such as these is to deplete the nutrient reserves in the roots by cutting the plant off at ground level.  This has to be done constantly while the plant is growing so that the root will eventually starve to death.  Checking the area every couple of days and cutting back any new growth above soil level is essential.  Pulling out or digging out plants along with its roots, will only encourage more root development as any piece of root remaining in the soil, will attempt to grow again.  Now is a good time to start this cutting back process before plants reach maturity and begin flowering as then you’ll also have to deal with plant spread via seeds.