Ground Covers for the PNW
Experimenting with Flora
One of my peculiar hobbies is pitting plants against each other, not in a "two plants enter, one plant leaves" Thunder dome-style battle, but rather in a quest to find the best plant for a particular purpose and how different varieties complement each other. This has given me firsthand experience in unconventional plant pairings and knowing which plants can truly fulfill their intended purpose.
Today, I am excited to share the results of a recent "ground cover competition" I conducted. The contenders were Lithodora, Green Sedums, Creeping Jenny, Thyme (as a ground cover, not the herb), Baby Tears, and some rather aggressive moss on the north side.
Initially, I didn't plant these ground covers with the intention of letting "the strongest survive," but that's exactly what has happened. These ground covers have all grown under and around a 100' cedar tree and rockery bed, and here is how they have fared as they have literally intertwined with each other.
Creeping Jenny: While it may look lovely in a container, it may not be the best choice for a large garden bed. It lacks the density needed to suppress weeds effectively, and when grown in semi to full sun, it turns a bright yellow color, which may or may not be desirable. On the positive side, Creeping Jenny can thrive under large maples with dry soil and is incredibly tough once established.
Baby Tears: I first fell in love with this ground cover during a garden tour on Bainbridge Island when I saw it planted between aggregate pavers, looking tidy and attractive. Baby Tears can grow under cedars and maples, but it requires consistent moisture during the summer months, or else it may turn brown and unsightly. For the competition, I planted it around various pavers, including flagstone, and found that it grows faster over thinner pavers. Trimming it back is not a big issue for a small area, but for larger areas, it can be quite labor-intensive.
Sedums: The workhorse of the garden, Sedum ground covers are not just for full sun, as they can also thrive in semi-shade conditions and under cedars and maples. However, in our competition, it is currently being outperformed by the Lithodora. My recommendation would be to use one type of Sedum ground cover in a planting bed instead of multiple varieties. Once it covers the bed, Sedums do an excellent job of suppressing weeds.
Thyme: The pink-blooming thyme looks stunning in the cedar tree bed, as it grows on several large rocks and receives full sun. However, I also have it planted near a bench seat by my pond, and I've noticed that natural moss is starting to invade the thyme, which doesn't look great. Moss tends to turn brown when exposed to sunny conditions, and it can also turn brown if you pour salt on a slug that happens to be gliding across the moss (I'll cover slugs in another post).
Last but certainly not least, we have our winner: Lithodora 'Grace Ward'
Why does Lithodora deserve our coveted groundcover trophy? Let me list the reasons:
It's evergreen.
It forms a dense mat that reaches a height of 3", effectively covering the ground.
The dense mat prevents weeds from getting sunlight. No sunlight means no weeds.
Long bloom time.
Note: Lithodora can overtake smaller plants, so I wouldn't recommend planting anything smaller than a 3'x3' plant/shrub in a bed where Lithodora is used as the groundcover. But despite this, it's a clear winner!