Kathleen wrote,

If there's that much arum in a wetland, it does need to come out. It will
have to be dug -- the tubers can survive herbicide application. It probably
arrived via garden debris being dumped, or on the treads of logging
equipment. Common garden Kniphofia has been found in Mt. Hood National
Forest (Oregon) far from cultivated land and probably arrived that way.
Arums have large seeds that don't travel far.

The state of Oregon is somewhat erratic in what it designates as invasive.
Arum italicum spreads rapidly in some gardens here, but not in others. It
seems to prefer moist, retentive soils such as the silty soils deposited by
rivers; some in my former garden on gritty subalpine soil barely survived.
Oregon has even declared Cyclamen coum invasive, and the only motive I can
imagine for that is that some official visited Boyd Kline's famous garden
in Medford and saw the decades-old drift of that species (C. hederifolium
is much more widely adapted, but I don't think it's on their list).

A. italicum is present in my new garden but I haven't started quelling it
yet as I don't need its spot for anything else (the Spanish bluebells
[Hyacinthoides campanulata] are a different matter!). I also have Arum
italicum var. albospathum, which one visitor this spring took for a
Zantedeschia because of its showy white spathes. I haven't planted it out
yet but will do so when it's dormant this summer, along with some other
Arum species that are taking up too much room in my bulb collection. I'm
not worried about these plants invading in the suburban neighborhood where
I now live, and they will make good ground cover in difficult sites near
conifers (mine or the neighbors').

Jane McGary
Portland, Oregon, USA

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