there's a few things that can be done, leave offerings to the plant spirits, i like to leave crystals. You can do something like a landtaking ritual/ or make contact with the land wights.
as far as spells, i don't know. I like to make bindrunes for growth and health and draw them onto the pots. You can make charged water with crystals in sunlight, the possibilities are endless.
a lot of old farmer superstitious rituals. when planting a turnip one is to say 'Thick as my wrist, long as my leg'