Vertical farming has been used in some form or another for years, but only recently have companies found the technology to make large-scale vertical farming a reality. Using hydroponic growing methods, leafy greens like spinach, kale and lettuce use just 5% of the usual water amount. Additionally, yields can be as high as 75x the normal yield of traditional methods, and production never really stops.
Growing seasons would become obsolete as specially designed LEDs supply the appropriate wavelength of light to the plants; increasing growth efficiency and growth management.
The next step in the vertical farming revolution is to expand operations to other plants, such as root/tubers, berry plants and miniature fruit-bearing trees.
Within the next few years, your salad might be one from the future: a future that hopefully has done away with the problem of hunger in the world.