i've been growing a lot of them for railings and sap lights. and i've been noticing that, if i go a couple in game days with out picking them, the single sprigs in the plots are just gone. the sprig clusters are still there, but the singles are gone. and if one of my plots had no sprigs go "green thumb" then the plot is just empty. not sure about anything else, as i've not grown anything but sprigs since the recent patch yesterday. but it shouldn't matter how long it takes before i decide to harvest them, i'm pretty sure none of the sprigs should disappear. 

Same for mushrooms, and fiber. Clovers before the updated would disappear but it appears anything that requires to be chopped is safe