Things we plant grow and things we don’t plant grow in the same space. The soil does not care about a seed’s origin. You can faithfully tend your landscaping with eyes focused at ground level and pull up each tiny weed as it appears, all the while missing other things growing up that cloak like your real plants. But there’s a day when something will catch your eye and you will realize that a plant in your landscaping does not belong. You might be amazed how tall this unwanted plant grew under the shadow of the legit plant and wonder how you missed it for so long.
That’s the hard thing about life, we don’t have control over everything and we can’t always see what’s hidden. I think what matters is not that we missed something to begin with, but what we do once we find the weed. If the plant doesn’t belong in your space, get busy removing it, no matter how hard or how long you have to pull.