Yes, you should salt the water for blanching. Salting enhances the flavor of the vegetables and helps to season them from the inside out.
Salting the water when blanching vegetables is crucial for several reasons. First, it seasons the vegetables, drawing out their natural flavors and making them more palatable. The salt penetrates the vegetables during the brief cooking process, resulting in a more evenly seasoned product. Second, the salt helps to preserve the vibrant color of the vegetables. The salt ions can help to stabilize the chlorophyll, preventing it from degrading and turning dull. Third, the salt can slightly raise the boiling point of the water, which can help to cook the vegetables more quickly and efficiently. Finally, the salt helps to maintain the texture of the vegetables, preventing them from becoming too soft or mushy. A general guideline is to use about 1-2 tablespoons of salt per gallon of water.
Don't overcrowd the blanching pot. Blanch vegetables in batches to ensure the water temperature doesn't drop too significantly, which can lead to uneven cooking and loss of color.