Common groundcovers in the Pacific Northwest

Snippin' & Stuffin'

One of my (admittedly odd) hobbies is pitting plants against each other. Not in a “two plants enter, one plant leaves” Thunderdome battle, but simply seeing which plant fills a particular need best, and which varieties work well together too.

This has a benefit in my work, as I have a lot of firsthand experience in odd plant pairings, and also which plants do the job you want them to do.

Today, I’m pleased to report the results of a recent “groundcover competition” I had. The contestants are: Lithodora, Green Sedums, Creeping Jenny, Thyme (groundcover not the herb), Baby Tears, and on the north side some rather aggressive moss.

I didn’t originally plant these groundcovers with the intention of “the strongest will survive”; however, that is indeed what has happened.  These groundcovers are all growing under & around a 100’ cedar tree & rockery bed.  Here is the rundown now that they have literally run into each other.

Creeping Jenny:  Lovely in a container, but not so much for a large garden bed. This is because it’s not dense enough to suppress weeds. Also, when it’s grown in a semi to full sun location, it takes on a bright yellow color, which may or may not be what you want.  On the upside, this groundcover will definitely grow under large maples with dry soil and it’s tough as nails once established.

Baby Tears:  I first fell in love with this groundcover on a Bainbridge Island garden tour when I saw them planted between aggregate pavers, and they looked so nice and tidy.  Baby tears can be grown under cedars and maples; however, they must remain moist during the summer months otherwise you will have a brown mat. For the competition, I planted it around various pavers including flagstone.  The thinner the paver the faster baby tears will grow over the paver.  This is not a big deal to clip this back if you have a small area, but for anything larger, well… can you see yourself on your hands and knees trimming a 30’ path of pavers?  Me neither.

Sedums:  The workhorse plant of the garden. Sedum groundcovers are not just for full sun, as they can grow in semi-shade conditions and under cedars and maples. That said, in our competition, it is currently being overtaken by the lithordora.  My advice: use one type of sedum groundcover in a planting bed, not 12 different varieties.  Sedums do a great job at suppressing the weeds once it covers the bed.

Thyme:  The pink-blooming thyme looks great in the cedar tree bed, as it is growing on several large rocks and also receives full sun.  That said, I also have this planted near a bench seat by my pond, and the natural moss is starting to invade the thyme, which is not a great look.  Moss turns brown when it’s growing sunny conditions.  Moss also turns brown if you pour salt on a slug that happens to be gliding across the moss (I’ll cover slugs in another posting.)

Last (but certainly not least), we have our winner: Lithodora ‘Grace Ward’

Why does Lithodora get our coveted groundcover trophy? Let’s list the reasons:

  • It’s evergreen.
  • It creates a dense 3” high mat that really covers the ground.
  • The dense mat means weeds do not see the light of day. No light = no weeds.
  • Long bloom time

Note: Lithodora will overtake any smaller plants.  Personally I wouldn’t plant anything less than 3’x3’ plant/shrub in a bed that uses Lithodora as the groundcover. But that aside, it’s a clear winner!

Hopefully this information will be useful to you when looking for a groundcover. All of the groundcovers I tested have merit, so for your particular application, perhaps one of the four non-winners suits you best. And as always, GardenGirl is here to help if you need it!