Stickanswered grow question 6 years ago Clover, rye, mustard, beans, kale, are all marvelous ways to set up a cover-crop. Those plants (especially beans, clover, and rye) sequester nitrogen into the soil for your cannabis plants to use later. You can use cover-crops whenever you want. To be really effective, it should remain in place for months/years. Hope this helps, keep us up-to-date and happy growing!