Microbes & Beneficial Bacteria

What a microbial inoculant does

You are not buying fertiliser. A microbial inoculant is a living culture that colonises the root zone and changes how well that zone works: it unlocks nutrients already sitting in the media, stretches how far the roots can forage, and occupies ground root pathogens would otherwise take. Use it with a feed, never as the feed.

Three jobs: mycorrhizae, bacteria and trichoderma

Mycorrhizal fungi

Mycorrhizae partner with the root and become an extension of it, gathering water and nutrients from further out than roots reach on their own. Xtreme Gardening Mykos is one species on purpose — Rhizophagus intraradices, formerly Glomus intraradices — with no trichoderma and no ectomycorrhizae, so the contents are known. SNT Mycobiome carries four species of arbuscular endomycorrhizal fungi. Both are sold as granules and as wettable powders.

Beneficial bacteria

Bacteria act faster and do a different job: they cycle nutrients, free what is locked in the media, and drive root growth. Tribus Original is a liquid of three Bacillus species — subtilis, amyloliquefaciens and pumilus — and is stated not to form problematic biofilm in hydroponic applications, the usual worry when something live goes in a tank. BBA Max Roots is a liquid inoculant for DWC, coco, soil and flood-and-drain; Mammoth P is aimed at phosphorus cycling; Azos is a nitrogen-fixing bacterium for cloning and transplanting.

Trichoderma and broad-spectrum blends

Trichoderma are fungi that sit on the root surface and hold that ground against pathogens. On this page they come inside blends, not as a standalone: Plant Success Great White carries 16 species of mycorrhizal fungi, 14 beneficial bacteria and 2 trichoderma, and W2G Probiotic carries 16 endo and ecto mycorrhizal species, 8 trichoderma and 57 bacteria at 1.4 billion colony-forming units per gram. A blend occupies more of the biology; pick a single species when you want a repeatable result.

Using a microbial inoculant

1. Get it onto the root. Mycorrhizae only colonise if they physically touch root tissue. Dust the root ball at transplant, dib granules into the hole, or dip cuttings in a wettable-powder slurry. Most of a surface sprinkle on an established pot is wasted.
2. Inoculate once, then top up the bacteria. Once mycorrhizae take hold they stay for the life of the root system. Bacterial products are consumables — reapply through the cycle as the label directs.
3. Match the form to the system. Granules for soil, beds and transplanting. Wettable powders for dips and drenches. Liquids for reservoirs, drippers and recirculating systems.
4. Do not sterilise and inoculate together. Hypochlorous acid, peroxide and systemic fungicides do not tell your pathogens from your inoculant. Choose one root-zone strategy and stay with it.
5. Treat them as perishable. These are living cultures. Check dates, keep them cool and out of sunlight, and mix fresh rather than leaving a brewed solution standing.

Microbes or root stimulators — what is the difference?

A root stimulator is defined by the job it does; a microbial inoculant is defined by what is in the bottle. Some products qualify as both, which is why they sit in both collections. Read the label: organisms, species or colony-forming units means inoculant, and it belongs here. Hormones, vitamins, kelp or amino acids means stimulant, and that lives in root stimulators. They stack — the stimulant pushes the plant, the inoculant improves the root zone it is pushing into.

Because an inoculant is not a feed, you still buy a nutrient programme. Organic nutrients sit naturally with biology — organic inputs need microbes to release them — and hydroponic nutrients covers the mineral side. If the roots are already struggling, Yellow Leaves on Plants? walks through the likely causes before you add another bottle.