Silica, mycorrhizae, foliar sprays and boosters: what is actually proven?

Shops sell lots of extras. Get light, water and a basic feed right first.

What the research says

• Bloom boosters and extra phosphorus: one flowering-stage DWC model predicted a maximum around 59 mg/L elemental phosphorus for Gelato. A separate two-cultivar perlite study found 30 to 90 mg/L supported plant function. These trials don’t prove every booster fails, but don’t assume extra P will improve yield.

Evidence needs context

• Silica: cannabis-specific work does exist. A 2024 hemp study tested silicate and phosphite together. Leaf silicon increased, while the reported flower-yield increase had p = 0.087, above the conventional 0.05 significance threshold. It didn’t test silicon on its own. Follow product-specific mixing directions, and don’t mix concentrates together.
• Mycorrhizal fungi and beneficial microbes: controlled hemp trials have reported benefits from particular inocula. For example, a 2022 study in sterilized, low-phosphorus soil found two fungal inocula had different effects. That doesn’t establish a benefit for every commercial product in already fertile potting mix or hydroponics. Mycorrhizal fungi need a compatible root partner, and product viability and conditions matter.
• Foliar feeding: a quick spray can sometimes help in the vegetative stage. Don’t spray flowering buds, because it traps moisture and can bring mold.

A sensible approach

1. Change one thing at a time so you know what worked.
2. Keep a notebook.
3. If a product makes big promises with no studies behind it, skip it.