Since hydroponic setups are often limited by available space and the configuration of the system, small plants are the easiest to accommodate. Shallow root systems are similarly well-suited to a hydroponic setup, which is why root vegetables are often disregarded. If you're growing hydroponically for market or even to feed your own family, fast growing crops will give you more yield per square foot.
Plants with lower nutrient demands are also easier (and less expensive) to produce. Leafy plants like spinach, lettuce, and herbs, for example, are less demanding than fruiting crops like tomatoes, strawberries, or beans. Above all, plants that are picky about their environment or extremely sensitive to even small variations in temperature, for example, definitely don't qualify as easy.
