Re: SPEC: Iris pseudacorus

Anner replied to Rodney's caution about planting I. pseudacorus where seed can escape to natural waterways: >>..this caveat must then apply to the other water irises as
well. For surely they produce seed which is borne by water eventually to rest
in congenial circumstances. Even natives may clog waterways, at least in
theory. If we propose to remark upon this invasive potential in the golden
flag, we should also note it in the others..<<

The problem isn't about clogging waterways, but displacing native plants, thereby disturbing natural ecosystem/habitats.  Seen that way, by definition I. pseud. isn't a problem in regions where it's native.  Nor would I. virginica or I. versicolor be here.

Not all introduced water irises have the vigor to compete effectively with what might grow in those creeks and lakes in the absence of the introduced iris seed.   Yellow flag seems to.  I don't think that Japanese iris do. I don't know about others.

Distinctions can be made, and it's not just a question of dogmatically opposing non-native plantings.  Multiflora rose seeds have enormous vitality and vigor, and quickly make R. multiflora a serious pest where it's planted in volume.  Many other non-native shrub roses, despite their hips being equally attractive to birds, do not spring up everywhere, ruining pasture and choking out the native understory at woods edges the way multiflora does.  How much better our lives would be if the U.S. Soil Conservation service had paused to do a little testing, and promoted 'Silver Moon' for hedging instead!   

It's mass plantings by institutions and governments, not individual gardeners, that have created some of the worst invasive nightmares in North America -- autumn olive, kudzu, multiflora rose, amur and Japanese honeysuckles.  But gardeners living near intact habitat can still benefit from reasonable advice like Rodney's.  

Nell

Nell Lancaster, Lexington VA  USDA z6b   <nlancaster@rockbridge.net>

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