Mine is slightly taller than that now. about 8 inches, but I'm in somewhat warmer zone than you. I suggest you feed it, compost is good. Mulching keeps ground moist and controls weeds. Wait to do this when plants are slightly taller. Reason; there may be more sprouts coming out of ground , and you don't want to put compost on top that may prevent them from coming thru. JMO.My rhubarb at the back of the garage is about 2" tall. I am glad that it is coming back, the roofers trampled it pretty good a couple of years ago and it wasn't very healthy last year.
Should I mulch around the plants or anything? Maybe put down some compost - then mulch over that?