Arum italicum

Jane McGary
Wed, 23 Apr 2014 09:39:36 PDT
Kathleen wrote,
>Working on a wetland mitigation site last week, I found three 
>patches and two seedlings of Arum italicum. My question to the PBS 
>members in temperate climates is this:  How invasive is this 
>species? It's listed as invasive in the state of Oregon, which is 25 
>miles to the south, and it's in a natural area that is supposed to 
>be left alone. I suspect it needs to come out, though that may be 
>difficult, given the likelihood of deeply rooted corms.

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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