Mycorrhizae, Trichoderma and Beneficial Bacteria for Plants
Mycorrhizae are fungi that live in partnership with plant roots; Trichoderma is another fungus, and beneficial bacteria are the third group of microbes sold for the root zone. This guide explains what each does, how and when to add them in soil, coco and hydro, which to choose and what kills them. You will find most of them in our root products section, alongside the root stimulants.
What mycorrhizal fungi do for plants
Mycorrhizal fungi grow with the roots and spread through the growing medium in fine threads. The Great White page says these networks of fungal filaments improve the roots' uptake of nutrients and water, and that the fungi release enzymes that unlock key elements for the plant.
The page names two kinds, ecto- and endo-mycorrhizae, and says the endo kind penetrates the root tissue itself. As a rule, most crops, tomatoes and chillies among them, partner the endo kind; ecto-mycorrhizae are mostly found on trees, and cabbage-family plants form neither. The Ecothrive Biosys page names the endo kind.
Trichoderma and beneficial bacteria
Trichoderma is a fungus too, but sold for protection. Great White carries two kinds, koningii and harzianum, which its page says protect the plant against pathogenic fungi such as some species of Fusarium and Pythium. Pythium, a water mould, is the usual cause of root rot (see our root rot guide).
Beneficial bacteria are sold to crowd out the harmful ones. The Great White page says they stop harmful bacteria and fungal pathogens reaching a critical mass; the Psycho Myco Mighty Mycorrhizae page describes a blend of beneficial bacteria that crowd out pathogens and break nutrients down into forms plants absorb more easily. Biobizz Microbes, its page says, also break down organic matter in the medium.
The microbial products we sell compared
| Product | What its page lists | Form | Medium | Dose on its page |
|---|---|---|---|---|
| Great White | 15 species of mycorrhizal fungi, 11 bacteria, 2 kinds of Trichoderma | Soluble powder | Soil, coco, hydro | 5 g per 25 litres |
| Ecothrive Biosys | Endo-mycorrhizae, Trichoderma, Pseudomonas, Azospirillum, Bacillus | Water-soluble powder | Soil, coco, hydro, propagation | Rate on the label |
| Plant Magic Oldtimer Granules | Mycorrhizal fungi, 20+ kinds of bacteria, bio-stimulants | Granules | Soil or coco | A healthy sprinkle round the potting hole |
| Biobizz Microbes | Bacteria and fungi | Soluble powder | Any | 0.2-0.4 g per litre, weekly |
| Psycho Myco Mighty Mycorrhizae | Beneficial microbes | – | Hydro, including DWC and NFT | Rate on the label |
| Advanced Nutrients Voodoo Juice | Beneficial bacteria | Liquid | All media | 2 ml per litre, grow and bloom weeks 1-2 |
| Advanced Nutrients Piranha | Beneficial fungi | Liquid | – | Rate on the label |
| Hydrotops Bactivator | Bacteria and microbes; organic | Liquid | Soil, coco, hydro | Rate on the label |
| Photosynthesis Plus | Beneficial microorganisms | Liquid | – | Rate on the label |
When to add them
Whatever the form, get them in contact with the roots (the Great White and Oldtimer Granules pages both say so): granules round the planting hole, soluble powders dusted on or dissolved in the water, liquids in the water or feed.
- Seeds: the Great White page says to dust them during germination, and the planting hole once they have sprouted.
- Cuttings: if you use a rooting hormone such as Clonex gel, apply a layer of Great White after it and tap off the excess, the Great White page says. Pre-soaking Rockwool Propagation Cubes? Add 1 scoop (5 g) per 10 litres to the soak.
- Potting on: dust the planting hole with Great White, or sprinkle Oldtimer Granules all round it, every time you pot up.
- Through the grow: in soil and coco, Great White weekly at 1 scoop (5 g) per 25 litres of nutrient solution; Biobizz Microbes weekly, twice when plants feed hardest (week by week in our Biobizz feed chart); Biosys from propagation through the plant's life. Voodoo Juice goes in grow and bloom weeks 1-2, when, its page says, the roots grow fastest.
Microbes in hydroponics
In hydroponics they go in the tank: Great White at each tank change, 1 scoop per 25 litres, mixed into some nutrient solution first so it dissolves fully, its page says. Psycho Myco is made for hydro: it mixes into the nutrient solution of deep water culture (DWC), NFT or any other hydroponic system, from seedling to harvest.
The other route is a sterile tank; you cannot have both. Silver Bullet Roots (silver ions and hydrogen peroxide) is sold as an alternative for growers who find beneficial-bacteria products less effective in hydro.
What kills them, and what feeds them
- No peroxide. Liquid Oxygen, a hydrogen peroxide solution, kills beneficial bacteria and fungi, its page says: use one approach or the other. The Oldtimer Granules and Photosynthesis Plus pages say the same.
- No chlorine. Chlorine and chloramine in tap water kill microbes, the Ecothrive Neutralise page says; our soil amendments guide gives its dose. Our water filters take chlorine out; if your supplier uses chloramine, ask us before choosing one (see our reverse osmosis guide). Athena Cleanse is a mild hypochlorous acid with powerful oxidative properties, its page says: check with us before using it with microbes.
- Feed them. Biobizz Microbes do best with Biobizz Grow, which carries food for them, their page says. Ecothrive recommend Biosys with Ecothrive Charge in soil and coco; Charge, its page says, feeds the microbes in the medium.
Which should I choose?
- Want them in the mix? Biobizz All Mix and Ugro XL Rhiza coco come with mycorrhizae, Jiffy Pro7 All+ Mix with beneficial bacteria and Root Riot cubes with beneficial fungi, their pages say.
- On a maker's feed chart? Use its microbe product: Microbes with Biobizz, Voodoo Juice with Advanced Nutrients (see our Advanced Nutrients feed chart; Piranha is not on it, its page says).
- Soil or coco: Great White, whose page sets out its use at every stage, or Biosys, which adds growth stimulants, with Charge.
- Organic soil: Oldtimer Granules at every potting up (a solid choice for organic growers, says its page), or Biobizz Microbes with Bio Grow.
- Hydro: one route, not both. Our rule of thumb (see our root rot guide) is a sterile tank with Silver Bullet Roots for a recirculating system such as NFT; if you choose microbes, Psycho Myco or Great White, with no peroxide in the tank.
Quick answers
What do mycorrhizae do?
They grow with the roots and spread fine fungal threads through the medium, which help the roots take up water and nutrients. They are living organisms, not a feed.
What is Trichoderma harzianum?
A species of Trichoderma, a fungus sold to protect the plant. Great White carries it with koningii; its page says they protect against pathogenic fungi such as some species of Fusarium and Pythium. Ecothrive Biosys lists Trichoderma too.
How do I use Great White mycorrhizae?
A soluble powder of microbes, not a rooting hormone. Dust it on seeds and in planting holes, or add 1 scoop (5 g) per 25 litres of nutrient solution: weekly in soil and coco, at each tank change in hydro.
What is in Ecothrive Biosys?
Endo-mycorrhizal fungi, Trichoderma, Pseudomonas, Azospirillum and Bacillus, with amino and humic acids, proteins, enzymes, carbohydrates and seaweed extract, in a water-soluble powder. Use it at the rate on the label, with Ecothrive Charge in soil and coco, as Ecothrive recommend.
More Growers' Guides
- Root stimulants and rooting gels
- Root rot (pythium)
- Soil amendments and living soil
- Hydroponics: the systems explained
Not sure what you need? Call the shop on 0117 971 3000 or pop in to the Bristol store and we'll help you pick.