Hi everyone, I am looking for a way to remove Creeping Buttercup from a lawn. Though there are small patches of grass without any buttercup (about 20% of the lawn), the rest of the area is covered with a mix of grass and buttercup. The ground slopes towards a green-belt with trees (non-coniferous) (trees about 6 feet from the edge of the lawn) and a fish bearing creek (about 20 feet away from the lawn). What are my options for getting rid of the buttercup? (a) Is a herbicide the best way of doing this? If yes, are either Roundup or triclopyr (Weed-B-Gone?)appropriate for my situation? I looked at the descriptions online for half-life of glyphosate and triclopyr in soil/water, but don't have enough experience to judge if these should be used near a creek and a dense stand of trees. (b) Is there any other chemical tratment that is more appropriate? (b) Using a herbicide or otherwise, when is a good time to do this in Vancouver? Now (December) or in the spring? (c) The lawn has not been mowed for 3 months (the grass is about 6 inches tall). Should it be mowed before applying any herbicide? (d) I am guessing that I would have to plant grass once the weeds are gone. I would be doing this from seed. When is the right time to start a cold-season grass in vancouver? (e) Should I pull out the buttercup by hand? (I've tries this - but cannot seem to remove the plant completely - especially the roots). Since I am new to gardening I am not sure if some tool (any particular kind of rake, for instance) would make this easier. Any suggestions/advice would be greatly appreciated!
Thought I'd post an update ... I attempted pulling out the weeds by hand - didn't help because I couldn't get all the roots out. And all the little bits that I couldn't remove start sprouting. Removed as much of the buttercup as possible by hand and with a lawn rake in March. Added some topsoil and overseeded the lawn. This didn't work either - though the grass covered some bare patches, the buttercup came back with renewed vigour. Used Later's Creeping Buttercup Killer for spot treatment on the buttercup leaves. The active ingredient is MCPA. I applied this once in the beginning of May and it cleared up most of the problem. Since then, I have been removing the buttercup by hand whenever it comes up. Have tried encouraging white clover to grow in the lawn - not sure if this competes with buttercup, but seems less aggressive.
Buttercup is favored by dampness. As with other weedy lawns yours is on a site that is favoring the flowers enough to allow them to grow in the grass. Where conditions are optimal for lawn grasses these dominate.
Unfortunately, my house is essentially the bottom of a valley, with very tall trees to the south/soutwest. So, I get all the rain water runoff, and no afternoon sunlight on the lawn (except in the winter - those trees are deciduous). I originally though soil compaction was also an issue - but it turned out that was not as bad as I had assumed.
