Ranunculus repens has been creeping up on me for thirty years. When I first moved west of the Cascades, I was dazzled by everything green, and more than happy for anything that covered the ground and survived without my having to lift a finger. Creeping Buttercup fits that bill, not only growing profusely, but producing cheery yellow blossoms to boot. True, by the end of the dry season it lost its luster, but once the rains returned it greened up again for the duration of the wet season.
It was only later, when I began working on forest restoration in earnest, that I began to question my tolerance for a plant that is apparently known as “devil” in the UK. However, for a long time I had so many higher priorities to contend with (ivy, holly, laurel, blackberry, broom, etc.) that it has only been in the last year or so that I’ve been able to turn my attention to Creeping Buttercup.
Creeping Buttercup’s reproductive stolons (runners) rapidly expand its range and fill gaps between plants, and its abundant seeds supposedly stay viable in the soil for over 20 years. Almost any soil in the Puget Lowlands will satisfy its needs, though it especially loves places that stay wet all year, and in which its masses of fibrous roots can take over the top 4” of soil.
Like many other invasive plants, the wet season is a good time to remove it because roots come out more easily when the ground is soft. My first course of action is usually the Bradley Method to contain it. For an isolated plant, like a newbie at the end of a runner, I pry under it with a hand trowel to loosen the soil, then wiggle and pull. Even the most careful hand weeding misses some of the plants, and the resulting soil disturbance invites new sprouts from the seed bank. In short, long-term control of Creeping Buttercup requires ongoing repeat weeding.
For solid mats of buttercup, I like to use a pitchfork to pry up a clump just enough to loosen the soil and enable the removal of the plants, one at a time. It’s slow going. It may seem quicker to use a cultivator to hoe it out, but the individual plants still need to be picked out by hand or they will usually keep growing.
I don’t usually remove whole patches except as a prelude to a dense planting of trees, shrubs, and/or herbaceous plants, dressed with a 3-6” layer of wood chips or bark. The planting area will have to be re-weeded for the foreseeable future, but in the long-term the competition from native plants will, hopefully, deter the devil buttercup from creeping back in and taking over again.