ARBICO Organics Root Build 240 Beneficial Mycorrhizae, 1 lbBeneficial Mycorrhizal Fungae Help Grow Healthier Plants That More Efficiently Use Nutrients and Water. ARBICO Organics Root Build 240 is a micronized mycorrhizal blend suitable for most crops! Soil preparation is imperative when readying plants and the growing environment for the upcoming season! ARBICO Organics Root Build 240 provides a mixture of mycorrhizae that aids most plants establish themselves. Mycorrhizal fungi form symbiotic relationships