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The Impact of Landscape Decisions

January 28, 2009

Since I love a cliche, I’ll just say it- it’s not easy being green. There’s a lot to think about, since the decisions we make in one yard can impact our neighbors and even folks so far downstream we’ll never even see them.

Plant choice is one obvious decision with a host of potential problems. There are some designers who have a very strict policy of natives-only planting. That’s not for me; I like my non-natives and exotics. However, it falls on the person making the plant choice to be careful not to introduce an invasive species into their area. How do we know what plants are invasive? Research is essential, and the internet is a great resource. The Virginia Native Plant Society has a great list of invasive plant sites here. Especially when using internet resources to find invasive plants, be sure you consider the source. Here in Northern Virginia, we’re in USDA Zone 7. A plant that’s invasive in Zone 9 may not be invasive here, because it may not survive our winters. Conversely, there are plants that can be used in Zones 4 or 5 with no worries, but the milder winters here would allow them to grow unchecked. A good trick is to read growth information about a plant you’re considering. If the tag says it grows “vigorously” or “aggressively,” you may want to check it out a little further before buying.

Unfortunately, garden centers (especially the big box stores) often don’t flag something as being potentially invasive. The burden is on you, the consumer, to make sure you’re buying an appropriate species.

Speaking of invasive plants, I feel I have to mention bamboo, since many species do very well here in Virginia. There are two major categories of bamboo- running and clumping. I’ll do a whole post on bamboo later, but the key facts are that running bamboos are extremely invasive, while clumping bamboos are not. It has to do with the rhizomes the plants send out and their growth structure. So, if you’re going to plant bamboo (I am), make sure that it’s a clumping variety- and be VERY certain that you’re buying it from a reputable source who knows what they’re selling you. More on this at a later date.

So what’s the big deal? A couple of seeds blow out of my yard and sprout, who cares? Well, if you garden in Virginia, I’m sure you’re familiar with kudzu. You can see it overtaking everything alongside Route 3 as you come into Culpeper during the warm months. Kudzu was brought over to the US from Japan in 1876 and widely promoted as both a forage crop and an ornamental. Well, it turns out the American Southeast is a great climate for kudzu and there are no natural predators. By 1953, the USDA considered it a pest weed. Since then we’ve put men on the moon, but we’ve had no luck eradicating kudzu.

There are probably hundreds of examples just like kudzu of well-intentioned people causing havoc in the ecosystem- gypsy moth caterpillars come to mind. We have a responsibility as good stewards to make informed decisions about changes we make. They aren’t always easy to correct after the fact. I’ll leave you with a great video I found today- it sparked the idea for this post- that illustrates how difficult it is to “fix” our mistakes in nature.

Click here for the Sad Saga of Macquarie Island

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4 Comments leave one →
  1. January 28, 2009 3:02 pm

    Dave, so good to read your thoughts about invasive plants. It is true that cold hardiness is one of the factors that determine whether a plant can become invasive. Another is the soil type – as you know, some plants do better in different soils. An interesting concept invasive species experts are exploring now is how nitrogen, an essential plant nutrient can be used as a limiting factor to control the spread of invasive plants!

  2. virginialandscaping permalink*
    January 28, 2009 3:13 pm

    Really- as in providing excesses of N? I know many of the first plants to pop up in disturbed soils love poor soils. Is this the idea? Do you have any links to the research?

  3. January 29, 2009 2:09 pm

    In most studies I’ve read the invasive stimulus would be an abundance of nitrogen – studies targeting invasive grass species in the Great Basin arid regions. It seems possible that nitrogen depletion might also contribute to non-native, exotic species in a plant community where native species require high soil nitrogen values . The main idea I derive from these studies is to be aware that the soil composition, nutrients, soil organisms, microbes etc. contribute to the vegetation dynamics of a site. You can get the PDF for the Great Basin ARS study by Edward Vasquez, Roger Sheley, and Tony Svejcar from the
    Invasive Plant Science and Management 1:304-314 2008, at the Eastern Oregon Ag Research Center site http://oregonstate.edu/dept/EOARC/researchhome/documents/610.pdf.
    The article explains the concept and has a good bibliography.

  4. virginialandscaping permalink*
    January 29, 2009 2:50 pm

    Great link, thanks! The reason I was thinking excess N as a means of limiting invasive growth is that I was just reading how Virginia’s soils are considered exceptionally rich for wine grapes, which is why vineyards here have to practice such intensive canopy management. So I figured, if our soil skews high in available N…

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