What are mycorrhizae, and which type is best for cannabis?

Mycorrhizae are microscopic, beneficial fungi that form a symbiotic relationship with plant roots. They act as a living extension of the root system. There are two primary types: endomycorrhizae and ectomycorrhizae. For cannabis cultivation, you need endomycorrhizae. These fungi physically penetrate the root cells to exchange nutrients and water, whereas ectomycorrhizae only coat the outside of the roots (and are better suited for trees and hardwoods).

How do mycorrhizal fungi improve cannabis yields?

Mycorrhizae develop a massive underground network of tiny threads called hyphae. This network reaches far beyond the plant's natural root zone to absorb essential water and nutrients—particularly phosphorus and nitrogen. In exchange, the plant feeds the fungi sugars produced during photosynthesis. This process drastically improves nutrient uptake, enhances drought resistance, protects against soil pathogens, and gives the plant the energy it needs to produce larger, more potent buds.

How and when should I apply mycorrhizae to my plants?

The primary goal is to get the mycorrhizal spores into direct physical contact with the plant's roots. You can apply mycorrhizal inoculants (available as powders, granules, or liquids) by mixing them into your potting soil, applying them directly to the root ball during transplanting, or watering them into the root zone. It is best to introduce mycorrhizae as early in the plant's life cycle as possible—such as during seeding or early propagation—to maximize their benefits.

What can harm or kill the beneficial fungi in my soil?

Because mycorrhizae are living organisms, certain cultivation practices can destroy them. Avoid using heavy chemical or synthetic fertilizers, as they inhibit the fungi from forming a connection with the roots. Additionally, systemic chemical fungicides will kill the mycorrhizae outright. Finally, avoid excessive physical tilling of your soil, as this tears apart the delicate hyphal networks the fungi have built. To keep your fungi thriving, stick to organic practices and maintain a slightly acidic to neutral soil pH.