Weeds: A Stitch in Time Saves Nine–Yellow Flag Iris

Bag full of iris seed capsules and root sections

Bag full of iris seed capsules and root sections bound for landfill (don’t compost!)

Weeds are a fact of life for every farmer, forester, ecologist, gardener, and property owner.  Plants, like all living things, are concerned with survival and reproduction and mankind has assisted in this endeavor, both to our glee and to our dismay. Some weeds are only “obnoxious”, or “a pain in the grass” as Kitsap County Noxious Weed Coordinator Dana Coggon is fond of saying.  Others are noxious weeds, a legally defined term. In Washington, 50% of all invasive, noxious weeds have escaped from gardens; the remainder have been accidentally introduced by travel and trade.

My current weed challenge is a formidable one of the noxious, escaped-from-gardens kind.  Our large, nearly one acre pond, with it’s year round moist ground and many visiting birds, is a perfect environment for weeds to thrive in the vegetative buffer  surrounding the waters edge.  When we purchased our property in the early 90’s, the pond was mowed to the edge and surrounded by nothing but turf.  In 20 years we have planted a zillion plants around the pond with birds and wind delivering a variety of volunteer natives.  Now the water is obscured from view in areas, according to our landscape plan.

The vegetative buffer is the life blood of our yard and as it has increased and grown up, so have the number of creatures we witness from birds to dragonflies to salamanders.  The buffer is an amazingly dense, protective habitat.  I have always hand weeded around the pond, yanking Himalayan and evergreen blackberries from day one, but doing so gets both harder and easier yearly.  In other words, the more beneficial, native plants get established and sizable, the better they outcompete and shade out weed seedlings, reducing the number to pull.  This same situation makes tenacious noxious weeds more of a challenge.

pond viewBecause of the breadth and height of the buffer (over my head in some places), a plant can get a toe hold before I notice it, making removal more difficult.  This is what happened with the noxious weed yellow flag iris  (Iris pseudoacorus) which now covers massive areas of the pond, growing in water as much as 30″ deep.  Except for bloom time in late spring when it’s yellow flowers are beacons; the grassy, long, sword-like foliage blends in with the cat tails.  Closer examination requires bushwhacking through salal and donning hip waders.

The Negative Impacts of Yellow Flag Iris

The term ‘noxious weeds’ includes non-native grasses, flowering plants, shrubs and trees as well as aquatic plants that invade wetlands, rivers, lakes and shorelines.  Like many noxious weeds, yellow flag outcompetes native plants.  In the wetland environment, yellow flag creates a monoculture that reduces the ability of populations of waterfowl, and other wildlife to support themselves.  Living things that rely on native plants for food or specific habitat for reproduction and life cycle completion are negatively impacted by yellow flag’s ability to clog waterways and displace natives like rushes and sedges.  It is also toxic to livestock, avoided by most herbivores, and causes skin irritation in humans.  Yellow flag is considered invasive in Vermont, Virginia, Connecticut, Massachusetts as well as New Zealand and Australia.

My Control Plan

Foliage only for yard waste recycle--no roots or seeds!

Foliage only for yard waste recycle–no roots or seeds!

My own lack of knowledge allowed this plant to thrive for too long, making eradiation harder.  If only I had acted on removing it when I first learned its classification as Class C noxious weed in Washington, I wouldn’t have needed to remove 2 utility trailers full of yellow flag iris over the long labor day weekend in 2013.  Nor would I likely be working towards a 3-5 year eradication plan with Dana Coggon’s advice.  “A stitch in time saves nine” is the weeder’s mantra.  Or as Dana’s weed newsletters state: “One a day keeps a million away”.

Blooms in late April, early May in W Washington

Blooms in late April, early May in W Washington

Two years ago, when the yellow flowers showed up on the opposite side of the pond, Istarted annually removing all the fruit capsules from the iris to at least prevent spread from seed.  One of the reasons yellow flag is such a daunting noxious weed is that in addition to disk-like seeds that disperse with water movement, the perennial, rhizomatous roots spread laterally from the main plant and any fragments of root are capable of floating off and taking hold. Apparently, one continuous rhizome can support hundreds of flowering plants.

The easiest time of the year for me to remove the 4 angled fruit capsules is late summer when the water level of the pond is lowest.  I remove the individual seed capsules from the long stems and put them in trash bags for the landfill.  The remainder of the flowering stalk has no reproductive capacity and therefore goes in the regular yard waste recycling.  The Kitsap County Noxious Weed Program in partnership with Kitsap County Solid Waste department offers special noxious weed bags that homeowners can use, with a voucher to dispose of the worst noxious weeds at county waste facilities at no charge.

unripe and ripe seed capsules

unripe and ripe seed capsules

Last year my control efforts redoubled per a new handout that Dana created on controlling yellow flag, which includes a new tactic that I hadn’t previously considered–cutting all leaves and stems below the water line.  The idea being, reduce the plant’s ability to photosynthesize, therefore starving the root of energy.  The research she found on this technique states it to be most effective if the plants are cut before flowering–for my area of Washington, that’s March.  Hmmm. that’s when my pond’s water level is the highest.  However, that’s also before many of the native plants surrounding my pond leaf out, which may help somewhat with access.

Last year I cut back all the iris foliage below the waterline, removed all the seed capsules (or so I thought) and yanked any seedlings that I could find.  I did this over labor day weekend, which may not be as effective as doing it in March, but it’s better than nothing.  By September, the plants have collected and stored a powerful amount of food in their strong, persistent roots, but not having another 2 months to store more energy before going dormant should help somewhat.  So begins my 3-5 year eradication plan.

New iris leaves coming up from where I cut them off last fall

New iris leaves coming up from where I cut them off last fall

As I write this in February of 2014, the foliage of the pond’s edge is dormant, making the iris’ foliage very clear and definable.  Though I cut all the iris leaves below the surface of the water last September, they are peaking through, robust and defiant.   If the pond weren’t frozen right now, it would be a good time to cut the foliage back because it is visible and more accessible than any other time of the year.  Not to mention that we have had an unusually dry winter, and the pond’s level is lower than in previous winters–again, easier access.

Last week, when the pond froze over, I went out to take photographs.  On closer inspection of the surface, I was dismayed by the number of iris seeds (they float, which allows for their tenacious spread) imbedded in the surface of the ice.  They are very distinctive–flat disks, burnt orange in color when ripe and relatively large.  I plucked a handful that I could reach by the edge and put them in the trash.  In this major battle, every little bit helps.

Iris seeds frozen on pond surface

Iris seeds frozen on pond surface

And here I had thought I had cut off all last year’s seed heads.  Arrg!

This year I plan to add a fourth tactic when I start digging the most accessible plants out by the rhizomes, though this inevitably will leave pieces of root to re-grow.    The idea is that with each technique I employ with yellow flag iris, the better control I will get over time.  My goal is at some date in the future I will spend a few hours a year with scouting and control, as opposed to this last year’s four full days of removal.

Learn More

To read Kitsap County Noxious Weed Program’s information on yellow flag iris and control options: http://county.wsu.edu/kitsap/nrs/noxious/Pages/Weeds.aspx Click on “Yellow flag” or peruse the other excellent resources on that page.

For more information on yellow flag iris, visit the Washington State Noxious Weed Website: http://www.nwcb.wa.gov/siteFiles/Yellow_flag_iris.pdf

©Colleen Miko 2014

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About Colleen Miko

Colleen Miko is a certified professional horticulturist with 20 years experience in landscape design who has designed award winning gardens for the NW Flower & Garden Show as well as HGTV’s “Landscaper’s Challenge”. Colleen is freelance garden writer and speaker.
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