Legacy Plants or weeds

Mary Sue Ittner msittner@mcn.org
Mon, 15 Mar 2010 13:03:43 PDT
Not too long ago Kathleen Sayce started a thread on plants that you 
find lasting with little care in the garden or in abandoned 
homesteads. I posted some of the ones from my area of coastal 
Northern California with the note that some of them had weed 
potential. In the past we have also discussed the distinction between 
plants that just persist and those that replace native plants. The 
latter is far worse since not only do you lose diversity, but the new 
plant may or may not have anything to offer wildlife.

The quarterly newsletter of the California Invasive Plant Council in 
its winter issue published a red alert for potentially new species 
not previously considered invasive in California or species that have 
been recognized but are expanding rapidly in their area or moving 
into new areas. In the top ten are these:
Romulea rosea (the variety that is known as australis that is rampant 
in Australia even though native to South Africa). I has been found on 
dry sandy or hard-packed soils in the San Francisco Bay Area and 
other sites along the central and north coast but is expanding from 
disturbed areas and roads along the roast to coastal and interior 
grasslands in Sonoma county.

Watsonia meriana (var. bulbillifera) has been of concern to those of 
us who live on the Mendocino Sonoma coast for some time as it forms 
dense stands along Highway One replacing other plants. It is now 
spreading south and north from these counties from roadsides and 
waste areas to marshes, woodlands and grasslands adjacent to the 
roadside. I asked NARGS to remove Watsonia meriana from their seed 
exchange when I saw it listed and I don't think it should be on our 
BX lists either. You could just not offer it to residents who live in 
Mediterranean areas, but the easiest way would be not to offer it at all.

Also making the list, but not in the top ten:
Crocosmia x crocosmiflora  - Marin County
Iris foetidissima - East Bay  (Alameda, Contra Costa? counties)
Kniphofia uvaria - Sonoma and Mendocino coast

These new ones are all reported from Northern California and all but 
one are South African plants. Since the Crocosmia is from a summer 
rainfall area it needs some summer water to thrive, but not a lot. It 
appears that there were more reported weeds in northern California 
than in central or southern California. I don't know if that is just 
because there are more people reporting in these areas or if the very 
dry years we have had the last few years before this one in southern 
California have helped prevent the weeds from expanding.

Mary Sue

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