May is a great time for you to weed and mulch.
The soil is soft and carefully removing quack grass from planting beds is possible at this time. If you want to freshen things up a bit a very light layer of mulch can improve the looks of your landscape. Avoid applying heavy layers of organic mulches like bark or wood chips because you just raise the level of soil as these materials break down, creating other problems.
If you already have mulch “volcanoes” around your plants, think about removing that decayed material to the original soil level. You can use the composted material that you remove for a base for a raised bed or in the bottom of containers. Then spread a light layer of fresh mulch over those areas. Think about ground cover plants to replace mulches as a long-term solution instead of constantly adding mulch to your planting beds.