I rinse em off ,stab em with a fork so that the point's on the fork are not exposed, and plop em in the tank.
Can leave vegetable matter in the tank for up to two day's if you are so inclined.(have done so on weekend fishing trip's)
The vegetable matter contains none of the animal proteins that most fish food's contain(fish,shrimp,krill etc) so although it may cloud the water (depending on how big a piece you use ,tank size) It won't give rise to ammonia level's in my expierience.(whole zuchinni in ten gal might)
Most times,,I place the vegetable matter in the tank at light's out for the day,,and remove it the following day same time.
Oak,Birch leaves,are left in the tank till there's nothing left for like the vegetables,,they don't contain the animal protein's (shrimp,krill,fish,etc).