Research: Spacing Perennial Plugs with Existing Grasses in a Restoration Site



Andropgon virginicus , Broom Sedge, a native clump forming grass

In easy order multiples, our “Deep Plug” offers more roots for the money. More roots means quicker establishment when planted directly in the landscape with less post installation maintenance. The “Deep Plug” when potted into larger containers can improve “turn around” by as much as two weeks. When you compare our “Deep Plug” to the industry standard, we are sure you’ll see the advantages.

The above is from the “About Us” page on our website.  Sure we know there are many advantages to purchasing and using plugs in your projects. Admittedly, we are biased.Mjuch of our information is anecdotal, conclusions drawn from decades of hearing stories and feedback from our clients, peers and colleagues. This is what some may call qualitative research.

But we do not rely just on hear-say for our testimonials, there are numbers backing us up too.  We explore quantitative research out there as well.

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This 2004 research by Huddleston and Young of the Department of Environmental Horticulture at the University of California Davis.  Published in Restoration Ecology: The Journal of the Society for Ecological Restoration the experiments took place from 1999 – 2000.  Though this research is older than most folks prefer we think the results are relevant and may be helpful to a good many of our customers.

The authors state the purpose of this experiment is to explore the “effects of proximity to native neighbors on planting succession in a restoration setting.” In other words this study was looking to see when planting plugs of native plant species into an area with existing native plants, what is the effect on the existing natives and the planted plugs as a result of the introduced competition. This research focuses on a bunchgrass habitat in the Agate Desert in Southwestern Oregon. The site experienced fire damage as well as a failed restoration project by the Nature Conservancy in the past.  The site had invasion from exotic annual grasses.

Though, of course, the outcomes of this study are specific to this study alone there are some outcomes that can be considered when designing and installing a restoration project using plugs:

  • Plugs are effective for restoring degraded grasslands
  • Plugs planted 18 cm from the existing plants fared much better than plugs planted less than 6 cm from exiting native perennial grasses
  • Planting plugs 18 cm from existing native perennial grasses resulted in more growth and reproduction than in plants planted 6 cm from the plants
  • Proximity of neighboring species has an effect on initial plant growth and reproduction
  • Competition for light results in increased above ground biomass
  • Planting perennials may be effective in suppression of exotic invasives
  • High diversity plantings initially increase population success in competition from exotics
  • Must understand the history and ecology of the site

We know you all have been working hard and experiencing successes and challenges. Please keep sharing your stories and results, it helps us understand our product and our purpose.

PS> For those of you in academics – we have noticed a significant dearth of research relating to perennial plug survival and effects in restoration and landscape conditions as well as published research relating to growing herbaceous perennial plugs. There is, however, a lot of research on bedding plant plug production. If you know of any recent research pass the publication links or titles on to us and we will share them.


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