Amur Tamarisk

(Question)

Doug Reberg here from the Stratford and District Horticultural Society. I’m currently preparing an online guide to public gardens of Stratford, which has taken me into gardens I hadn’t visited for quite some time. The Catharine East garden is one, a lovely area showcasing shrubs and trees.
One of the shrubs is an c. I find it quite lovely, but I also found it is regarded as a highly invasive species in some areas (there’s an alarming photograph on the web of a section of The Colorado River literally plugged with the stuff). But some local garden centres sell it (Sheridan, for one), and the specimen in the Catharine East Garden seems to have been well-behaved, although it’s quite near the Avon River. I think it was planted about 1990, which is quite a long field trial. Meanwhile,, The Ontario Invasive Plant Council included tamarisk in its list of “alert plants” that “can be invasive in natural settings.”

I’m wondering if our cold winters (Stratford is zone 5b, I believe) make it a safe and enjoyable plant choice for this area. At what point in Ontario should the plant be avoided?

I’m trying to encourage visits to less frequently seen gardens in Stratford, but perhaps my encouragement to Catharine East visitors should include a waning note about tamarisk.

Thanks so much for your help!

Doug Reberg

(Answer)

Hello Doug;

It sounds like an enjoyable project you have endeavored upon, which brings you into contact with many interesting plants.

Yes, the Amur Tamarix is one of those interesting species not seen that often that can provide an interesting or even surprising element in the garden.  The research that I find is a bit mixed in terms of its viability in Ontario for being a successful invasive species in the wild;  although as you pointed, out the  Ontario Invasive Plant Council included it in its list of “alert plants” that “can be invasive in natural settings.”

I am providing you with some links which detail what is their ecological niche and how they  invade and take over these niches. To summarize, the tamarisk tends to invade riparian shorelines (similar to the photo you referenced of the Colorado River). It also like good drainage and is known as the ‘salt cedar’, since it actually exudes salts back into the surrounding soil, thus eliminating other adjacent native plants.

Although Tamarix rates higher on the Invasive scale the farther south you go, (for instance in the US. midwest, southwest it is considered a noxious weed), it is viable down to even zone 3.  While it poses risks to specific ecological niches, it would seem wise to include your “waning” note to be wary of its invasive potential.

Best of luck with your online guide.

References:

http://bcinvasives.ca/invasive-species/identify/invasive-plants/tamarisk

http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=a401