Flagging away the flag iris

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The first time I realised there was a problem with our flag irises was when Mark intervened to pull a photo from a House and Garden feature on our garden a few years ago. It was a view similar to that above. “It’s a weed,” he said. “It is embarrassing to be shown with a weed.” It has taken a while, but this week, I have dug out the last of it.

The offending flag iris

The offending flag iris

The problem with Iris pseudacorus is its resilient and invasive ways. It can survive in water, even in salt water, beside water, on water as a floating mat of rhizomes and even just on heavy soils and flood-prone areas. It is also poisonous to both humans and stock so is not controlled by animals. It is on most New Zealand weed lists and some regional councils require active management to control its spread.

Behold the offending rhizomes

Behold the offending rhizomes

Our flag irises have never set much seed, though all the descriptions say that seeding is a problem. We would have acted faster, had we seen threatening seed set. But the rhizomes, the rhizomes! They are sign enough of an issue. They form a dense mat both on and just under the surface. It reminded me of digging out wild ginger with their ability to form a solid barrier, choking out other growth. It was heavy, muddy work digging them out and prising stray rhizomes from farthest reaches with me, precariously balanced. I did not want to end up in the stream at this time of the year.

We had them planted by running water; the upper reaches of the Waiau Stream flows through our park. It was clear that floods or any disturbance of the rhizomes could cause some to wash downstream and from there, populate the countryside. It would not have been an issue had they been by a self-contained pond with no means of escape.

True, we grow Primula helodoxa and that is sometimes flagged as a weed issue by waterways but we dead head it. It is the seeding that is problematic with that plant.

Iris sibirica

Iris sibirica

Lovely Higo irises

Lovely Higo irises

and Louisiana iris

and Louisiana iris

Fortunately there are alternatives to the flag iris which do not seem to be a weed problem and are arguably considerably prettier.  Iris sibirica, the Higos and the Louisianas are all happy in similar conditions and give us a League of Nations in our park – Northern Europe and Siberia, Japan and USA. We just happened to have plants of all hanging about waiting to be planted. So while the three patches of flag irises are now muddy and apparently bare, in a few months’ time, they may even be flowering again in hues other than yellow.

036We are enjoying the water meadow effect we are achieving in that area of the garden.

More Louisianas that Mark has been raising to plant out

More Louisianas that Mark has been raising to plant out

 

 

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3 thoughts on “Flagging away the flag iris

  1. William

    Directly opposite from you, at the top of the globe, half a world away in Sweden, Iris pseudacorus is a protected species!

    But of course it doesn’t grow invasively here, instead it grows sparsely in more or less wetlands.
    As you mention, it is poisonous and I doen’t know of any insects or other animals that feed on eat.

    1. Abbie Jury Post author

      Other countries’ treasures often become out of control triffids in New Zealand’s benign conditions – agapanthus, giant gunneras, pampas grass, honeysuckle, to name just a few. We could probably repopulate Sweden with this iris!

  2. Pingback: A water meadow | Tikorangi The Jury Garden

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