Salt (honeycomb for plants)

To get salt, it would either involve smelting a bottle of water acquired from an ocean biome, or through mining. The important thing is what it does: when used on a plant (crop, sapling, vine, etc.) it halts its growth. Crops will be frozen in the state they are currently in, vines will not grow any lower, and saplings will not mature into trees. It basically functions similar to how honeycomb works with copper blocks, but for plants.