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Friday - June 13, 2014

From: Natrona Heights, PA
Region: Mid-Atlantic
Topic: Groundcovers, Grasses or Grass-like
Title: Planting creeping phlox for a groundcover
Answered by: Nan Hampton

QUESTION:

Dear Mr. Smarty Plants, I live in Southwestern PA (zip code 15065). I have a small slope on my property that is hard for me to mow. I would like to cover it with creeping phlox, which I saw on this website is native to my state. My questions are: 1. What can I do to keep it from spreading onto the rest of my lawn? 2. I was thinking of killing the grass on the slope with vinegar, then pulling it out. Is that an environmentally sound idea? I read that creeping phlox likes a slightly acidic soil, so I'm guessing that the phlox will still take to the soil afterwards; would I be correct in assuming that? (If not, is there a better method I could use to remove the grass from the slope?) 3. I'm looking for something as low maintenance as possible. Should I expect to have to do a lot of weeding if I cover an area with creeping phlox? If so, is there a plant you could recommend to me as a good native groundcover that would require little weeding? Thank you so much for this forum!

ANSWER:

There are actually two native phlox with the common name "creeping phlox":

Phlox subulata (Creeping phlox) is evergreen and Phlox stolonifera (Creeping phlox) is semi-evergreen. Both are native to Pennsylvania. P. subulata is native to Allegheny County and P. stolonifera is native to adjacent Westmoreland County (click on Pennsylvania on the distribution maps on the USDA Plants Database pages to see the county distributions). I would imagine that you are interested in P. subulata since it is evergreen and native to your county. Here is more information about it from Missouri Botanical Garden and North Carolina State Cooperative Extension.

1. FineGardening.com says that you can cut back the phlox if it threatens to spread into areas where you don't want it.

2. In my opinion, the easiest and most effective way to rid an area of unwanted vegetation is by solarization as described on this page from Native American Seeds. Here is a description, Soil Solarization for Gardens & Landscapes, from University of California IPM Online and an article, Want to kill weeds? Then solarize them, from the Pittsburgh Post-Gazette. However, killing weeks using vinegar seems also to be effective. You can read this assessment of vinegar as a weedkiller, Vinegar Week Killer: Grandma's Recipe for Fast Weed Control, from The Garden Counselor Lawn Care to help you decide which would be the best method to use. According to this article it is unlikely that the application of vinegar will change the the soil pH significantly.

3. You are most likely going to have do weeding as the creeping phlox becomes established and forms a thick mat. Once it forms the mat weeding should not be a big problem. It will be able to form a thick mat only if the area gets full sun for at least 6 to 8 hours a day. If the area is in partial shade or is shaded for more than 6 hours, you might have trouble getting P. subulata to grow and form a thick mat. In that case you will need to choose another plant. Penn State Extension has recommendations for native groundcovers for various situations. For dry shade they recommend Carex pensylvanica (Pennsylvania sedge) and Heuchera americana (American alumroot). For wet or moist shade or part shade Asarum canadense (Canadian wild ginger) and Tiarella cordifolia (Heartleaf foamflower) are among the recommended species.