Answer: Sometimes Vinca minor does get very thick and can benefit from overhead trimming to thin it. You can do this in late winter or very early spring (before it starts to grow for the season) by mowing it off with the lawnmower set very high -- at its highest setting. You may also want to routinely mow or use your string trimmer along the perimeter to keep it in its designated area, or you can hand cut a wedge of soil to form a dividing line at the edge of the bed periodically to hold the line. You can also probably raise up the lights by extending their supports if that seems desirable, or easier still, just selectively trim back the vinca by hand right at each light so it allows the light to shine through at night. I hope this helps!
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