Mixed green leaf lettuce is crisp and has a sweet or bitter smell when the stalk is scratched, depending on the specific variety. The leaves also have a mildly sweet or semi-bitter flavor, and the bitterness often occurs in maturing greens versus young greens.
Spinach is a leafy green producing succulent, dark green, spoon-shaped leaves. It offers a subtle, yet assertive vegetal flavor often with iron or metallic notes. Depending upon variety and maturity, Spinach can be sweet, earthy, nutty and even tangy.