Confused about invasive plants? Take it to The Man!

by Susan
Ever experience pangs of doubt about a plant, product, or gardening technique you've just raved about or admitted to growing or using, like "Uh-oh, could this be a known enviro no-no and I'm the last person to know it?  Could I lose my Friends of Earth membership card over this?"

That's been my feeling ever since I posted a profile of Nandina domestic and was clued in to its very bad behavior in Texas and Virginia and then my very own county in Maryland.  Yet just as many people were telling me it posed no problem locally, so I was confused, wallowing in self-doubt.  I quickly demoted both the blog post and the website page to draft status.

But then I remembered that as close as my regular nursery is a major national hot-shot on the subject of invasive plants and because he's local to me, HE'D have an answer to the question: Can nandinas be grown safely in my region?  Or under what circumstances, or which cultivars?  See, the seemingly contradictory reports could be answered by all sorts of factors.  I'll dump the whole problem onto none other than John Peter Thompson, I declare to myself.  This guy.  (From his blog:)

Secretary National Invasive Species Council Advisory Committee; Member, Maryland Invasive Species Council; LBJ Wild Flower Center Sustainable Landscape Standards Vegetative Sub-Comm; Chesapeake Conservation Landscape Council; Landscape Comm, Chesapeake EcoTour Project; Past President, Maryland Nursery & Landscape Association (MNLA) and Mid Atlantic Exotic Pest Plant Council (MA-EPPC); Member PlantWise Advisory Comm.; President, National Agricultural Research Alliance - Beltsville; Chairman, The Behnke Nurseries Co.]

So I wrote, a phone call followed, and he's assured me he's hard at work finding an answer to the question, which interests him at least as much as it does me.  Nandina's now on his list of plants to research, right there with spirea and Vinca minor, and I eagerly await his results.

A current venue for dealing with such questions as plant invasiveness is the Sustainable Sites Initiative.  They're writing standards for certification, and John Peter's a welcome voice for big-picture pragmatism on the committee making the recommendations.  It's a similar role to the one he plays with the Maryland legislature.  There he provides science-based feedback on bills written by staffers with no scientific understanding of the subject, who've been known to write "feel-good" bills that are just bad regulation.  Having worked in the U.S. Congress for about 30 years, I'm so not surprised.

My friend Pam and I heard John Peter's talk last weekend at his family's nursery, and here's my report.   

Comments

[germi]

This is such a big and confusing issue - I'm glad someone with so many credentials is on the case!

[Nancy]

I'm really glad to hear that there are people working on what's invasive in what places. For example, I know Budleia can be invasive, but I've never seen it growing wild anyplace I've lived, so I've wondered if it is just invasive out west or something. Thanks for the tips on how to wrestle with these questions.

[queenie]

wow - this is important! The place we're moving from has a lot of [what I now know is] Nandina and I had been contemplating taking some young volunteers with us when we move.

I don't think I'll do so, now. . . . Thanks for the warning.

[Lisa at Greenbow]

I wondered about this nandina. I planted one just this past summer. It withstood the drought conditions and has been green all winter. Just what I wanted...if it isn't invasive. Isn't it sad that when you find something that does what you want it to it ends up being an invasive plant.

I also thought this about the silver lace vine. When I saw it at a local park along a fence line I pulled mine out of my garden. It is an amazing vine here with great potential in the garden...just too good it seems. I haven't read anything offficial about it but I don't have to read in a book or journal to be warned.

Same as I am seeing pampas grass in our area popping up along side the highways. Now that is scary with Fragmite already choking our marshes and wet lands. Fragmite makes purple loosestrife look benign.

[Michele Owens]

I am so glad to learn that somebody smart is addressing the curse called vinca! God, I hate that plant! It was so difficult to elimate, even in sandy soil--I mean, five years of yanking and it still comes back--that I cannot imagine trying to get it out of heavy clay.

[JT]

As a part of National Invasive Weed Awareness Week (2/24 thru 29), the arboretum at Cal State Fullerton is offering a lecture to help gardeners know and identify invasive plants. Maybe there's an event near you.

[Matilija]

Well, I learned something, and that is that Nandina domestica can be beautiful. It was once a common plant in commercial plantings here in southern California and it always looked ratty-- I could never understand why anyone would plant it. Now I'm thinking that s. California, even the irrigated parts, is just too dry to suit it. I rather doubt it's invasive here.

[Beth]

Now if we can just get nurseries to stop selling those plants deemed invasive in their respective states! Frustrating.

[Katherine Andrus]

Having spent more hours than I can count pulling English ivy, Japanese honeysuckle and multiflora roses out of our wooded back yard I am entirely sympathetic to any effort to rid the world of invasive plants, but we need a more reasonable definition of "invasive." In some cases, people use it to refer not only to the truly thuggish plants but to any to any plant that is non-native and spreads by rhizome or self-seeds -- that would include just about any effective ground-cover! I have even seen hellebore on lists of invasive plants -- now my hellebore does self-seed, but it is a long slow process to get more than a handful (though I do have a crop of about 500 hellebore foetidus seedlings if anyone is interested), and it is easy to yank out any unwanted seedlings (I personally can't stand to throw them on the compost pile so I am constantly hawking them to neighbors, friends, and complete strangers -- see above). Plus, as the original posting notes, some plants are invasive in one region (or microclimate) but perfectly well-behaved in another. My mother used to garden on the Eastern Shore (very sandy soil) and would complain bitterly about being overrun by plants that just stayed in one spot in my Northern Virginia heavy-clay garden.

I'd like to see a definition that takes into account the relative ease or difficulty of keeping a plant in check, how far seeds or spores travel, and competition with other plants. For example, I have no problem with vinca minor in my garden because it has shallow roots (easy to pull out), doesn't leap over the fence to my neighbor's yard, and allows bulbs and hellebores to come up through it (unlike the violets and ajuga which will choke out every other low-growing plant). This definition should be applied region by region, to give gardeners a better sense of what they should be worried about in their own gardens.