The last battle between the alien crystals and the plants was a failure. One crystal survived. Now their is one final attempt to destroy the crystals and it will determine the fate of the world. In order to save the Green land you must defeat all of the crystals that remain. The closer you place your plant to the crystal the faster the battle will take place. You can use symbiosis between your plants to increase the strength of the plant you are using to attach the crystals. The farther the two plants are from each other, the better. This is because symbiosis will weaken the plant giving it's energy away.