Guanos have been used for centuries as fertilizers for all kinds of plants. Happy Frog&tmreg. Cavern Culture&tm. Fertilizer is a proprietary blend of bat and seabird guano, rock phosphate, and soil microbes specially formulated to deliver the nutrition necessary for flowering and bud development. Mycorrhizae and bacteria are included to help increase root efficiency and convert nutrients into a form plants can use. Experience the tried-and-true successes of our ancestors with Cavern Culture in your own backyard.