My Achillea millefolium 'Sawa Sawa' Yarrow has the droops!
I purchased a small yarrow (Achillea) plant from a master gardener in Md. at a mother's day community affair. I planted it as she instructed me -- in the sun, and last year and this year it started to grow fine, but then got very large and toppled over on all four sides, leaving a gaping opening in the middle of the plant. See picture. Last year I cut it back but then it just barely did anything after that. I was hoping this year would be better, but again it came up, grew beautifully, and then just did another funnel shape "slump" and now looks like a mound of mush. Please tell me what to do. I thinned it out last year but it didn't help this year. It is well-watered but not over watered.
Carroll County Maryland horticulture
This is rather surprising. Typically this plant becomes a "thug" or weedy in most sunny gardens. Some of the limiting factors for growth can be too much moisture/poor, water retentive soils and too much shade. This is generally a plant that most people walk away from when planted, and just let it grow.
I have seen it become a bit floppy and tangled in some garden. You may possibly want to cut it back in early June to prevent legginess and do not fertilize.
From the picture it does not look like disease or insect related issues. There is a shadow in the picture the plant- is that some shading??
Can you provide any other pictures??