@Kardamom I love za’atar! My last roomie made some fantastic Kurdish dishes with it.
@ibstubro Yes, you can harvest from now until fall – end of August around here in MA, but you’re further south (I think) so that might extend the season a bit. Dark-colored clusters are usually the ripest, though sometimes the light pink ones will be unexpectedly ready. Best time to harvest is after several days of sunshine – rain tends to wash out the flavor a bit, so don’t harvest just after a shower. Also, gently part each berry cluster to check it is free of bugs. One final tip for Indian lemonade – after soaking in cold water in a pitcher, strain the liquid through a cheesecloth into another pitcher to catch the berries and their fuzz, which comes off in the soaking water.
Sumac with red berries is never poisonous – though the plant is a relative of the cashew and the mango, so people with allergies to those foods should take care. Otherwise, as long as it’s red it’s good to go. Poison sumac has white, smooth berries that droop down like grapes, and it grows in swamps. Edible sumac (usually staghorn or smooth) has red, hairy berries that grow upright, and it grows in well-drained soil on dry sites.
You can indeed make wine from sumac – reportedly a very tasty wine, at that. I have not done this, but will let you know if I do (or if you try it, let me know your results, please!). Googling “sumac wine” gives several hits; seems pretty straightforward. I do know that to make concentrate, soak four sets of eight drupes (the proper name for the berry clusters) in the same pitcher of cold water, for half an hour for each set. This can be frozen and reconstituted for the winter, or be made into a nice tart jelly.
Sumac berries vary in taste quite a bit from year to year, even on the same plant – so if you don’t like it the first time you try it, give it a shot again next year.