I took over a garden from a previous renter that had a row of monkey grass and some day lilies behind it. Now one of the two is growing a million offshoots, all about the same distance away from both kinds of plants (ca. 5 inches apart). Since both plants are related and the leaves look roughly the same - how can I tell if it's the lilies or the monkey grass spreading out? The lilies I would keep, the monkey grass I'd pull up. Right now it just looks messy, like my garden hasn't gotten a haircut in months, since the new leaves are several feet long...

Thanks for your help!