We planted one plant a few years ago & it has completely taken over and looks an eyesore
I had the same problem and chose to dig out the plants and their numerous sturdy roots. Another option is chemical control. It is difficult to get herbicide to penetrate waxy leaves. Use a surfactant to get herbicide to "stick". (try an internet search for herbicide surfactants) An herbicide that is for brush and contains triclopyr works better than glyphosate. Follow instructions on the labels. Shrubs/small trees are often killed by painting herbicide concentrate directly on cut stumps. However, there are many "stumps" to a large cotoneaster because it roots where branches touch the soil. On the other hand, it will be cut down at some point so consider this option. Stumps should be painted within an hour of being cut, the sooner the better.
We have a cotoneaster on a trellis. As last year we currently a lovely display of blossoms. But last year we had no berries. What can I do to ensure berries this year? Thank you. .
Blossoms are a good sign that the plant is generally healthy. When it comes to berry production, the main factors are usually pollination and plant variety. Many cotoneaster types are self-fertile, but some do rely on cross-pollination from another cotoneaster nearby. If you didn’t see any berries last year, it's possible that pollinators—like bees—were scarce during bloom time. To encourage berries this year, I’d focus on attracting pollinators by planting pollinator-friendly flowers nearby or even hand-pollinating if you’re up for it. Avoid spraying any insecticides while the plant is in bloom, as this can deter or harm bees. Also, be sure not to prune off new growth too early, as flowers—and later berries—develop on that newer wood. One other thing to consider is your soil—if it’s high in nitrogen, that can push the plant to focus on leaf growth instead of fruiting. A simple soil test can help you check your nutrient balance, and if needed, you could adjust with a more balanced or phosphorus-forward fertilizer. With good blooms already showing, your chances are promising if pollination and nutrients align.
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-soil.htm
https://www.gardeningknowhow.com/ornamental/shrubs/cotoneaster/growing-spreading-cotoneaster.htm