Answer: Onion grass is a bulb (not a grass) and it is difficult to control. You can try digging it out by hand, being sure to take all the baby bulbs that surround the main bulb. If you don't take out the little bulbs, you will just end up with more than when you started. Or, you can try using the herbicide glyphosate on it. In a flower bed, the wipe on method of applying it is usually safer than spraying since it will kill your flowers if it contacts them. The onion grass foliage does not absorb the chemical very well, so you may find it is more effective if you cut it down and then wipe or spray it onto the freshly cut ends. Another option can be smothering it. Trim the onion grass off short, cover it with several layers of newspaper, and mulch on top of that. Also, do not allow it to flower and set seed, and avoid tilling an area where it is growing as this will spread the bulbs and yield even more clumps of it. I hope this helps.
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