It's rare that any weeds can have the growth habits to invade a putting green surface, but occasionally weeds can show up.  We do not treat our greens with herbicides when the sprayer goes out, but we do use small amount to spot treat small patches of chickweed or pearlwort.  In particular, pearlwort has been very invasive over the past few years, growing more in the shade and moisture.  You will see yellowing patches of this plant on some of the greens over the next few weeks as we try to get rid of it.

In the picture, these untreated spots of pearlwort located on the 7th green take on minty green colour and can look like poa annua, but the tiny round seed head gives it away as an undesireable...