Yes, you do. While we’ve all pinched a berry from a backyard raspberry bush without a rinse, it’s best to wash berries before using them. They’re outside in the elements, where there’s plenty of dirt, dust and grit, never mind visiting birds, cats and other critters. There’s also a reasonable chance there may be a few little bugs clinging to your berries when you pick them. The more dirt on the berries, the more you should wash them. Plain water from the tap should suffice.
It goes without saying that berries from the store should also be washed. Even organic berries should be washed before eating; while there may not be chemicals to rinse off, there’s still dirt and other grime to be cleaned off before you use the berries for anything.
How best to wash berries? For blueberries, place them in a single layer in a mesh strainer and run water over them, shaking them around a little bit to make sure they’re all getting rinsed. For raspberries, do smaller batches and make sure you’re gentle with them, as they break apart and bruise easily. For strawberries, wash each berry individually, making sure you get under and around the green leafy part on top of each berry.
In all cases, it’s best to wash berries right before you use them. If you don’t, the added moisture on the berries can cause them to quickly go moldy, even if kept in the fridge.
If you’re planning to freeze berries, wash them as soon as you pick them, let them dry a bit on a paper towel one handful at a time, place them individually on a parchment-lined baking sheet without any berries touching each other, and pop the baking sheet in the freezer for an hour or two. Once they’re frozen, remove them from the parchment and place them in a freezer bag. Before you put the bag in the freezer, make sure you label it clearly to indicate not only the fruit and date they were frozen, but also to note that the fruit has been washed. That way, when you’re making a batch of muffins in November, you’ll know the berries are safe to use right out of the freezer bag.