Rhubarb

The clump on the left I would harvest some of that and enjoy it.
Keep an eye open for flower buds which come through from the bottom centre and remove when you see them.
As you are growing through membrane (by the look of it) I would use something like Miracle Gro to feed with, mine are in uncovered soil and get a handful of growmore or chicken pellets also water in long dry spells.
Harvest time from spring through to summer. February you can put a dustbin or similar over the clump to "force them" if it works you get long, pale, sweet sticks. If you force one clump don't harvest much more from it that year. How much to pick I would say always leave between a third and a half on the crown. the crown tends to stop producing new shoots around mid summer and the older ones are decidedly stringy.
One of mine has leaves through most winters the other disappears below ground in November.
As a child it all disappeared end of October until March.