What Is Mycorrhizal Fungi & How To Use It?

What Is Mycorrhizal Funghi

Mycorrhizal Fungi also commonly called rootgrow is often recommended when putting in woody plants like roses, shrubs and trees. The use of mycorrhizal fungi is said to enhance root growth and aid the uptake of nutrients from the soil. Many gardeners may be dubious about adding fungus to the soil so what is mycorrhizal fungi and what does it do?

What Is Mycorrhizal Fungi & How Does It Benefit Plants?

Mycorrhizal Funghi

Mycorrhizal fungi consist of many thousands of different types of fungus called mycorrhizae.

Nearly all soil, except heavily cultivated / disturbed soil or one treated with fungicides will contain these fungi already and that includes your garden. 

These mycorrhizae have a symbiotic relationship with plants in the fact that the fungus uses the plants sugar and carbon reserves as an energy source at the same time as supplying water and nutrients such as phosphorus to the plant. 

This relationship acts almost like a secondary root structure for the plant as it is able to draw on more moisture and nutrients than just by the plants roots alone.

Types of Mycorrhizal Fungi

There are two main types of mycorrhizal fungi and they can be differentiated by the way they interact with a plants roots:


These fungi are characterised by living on the surface of the plants roots and found on roughly 5 – 10% of plant species.


Are mycorrhizae that grow inside the roots of plants and exchange nutrients this way. This type are far more common and can be found on roughly 80% of plant species.

How It Is Sold

Mycorrhizal fungi is supplied as a type of clay based powder that has been inoculated with fungal spores which make it really simple to sprinkle onto a plants roots.

In most cases there are several different types of fungus including different species of ectomycorrhizae and endomycorrhizae so you don’t need to be concerned about your plant getting the right kind.

Often a brand names are often used such as rootgrow, rootmore or mycorr powder.

Is Mycorrhizal Fungi Necessary?

If soil already contains this fungi then is it necessary to add it?

Many plant breeders and gardening experts recommend the use of mycorrhizal fungi when putting in a new plant. They are often selling their own brand of additive so there may be some bias here.

I try to think pragmatically and pick and choose when it will do the most benefit. 

  • If you have a nutrient poor soil then the use of mycorrhizal powder is going to benefit the plant as the fungi allows the plant to absorb more of the nutrients available.
  • If the soil has been disturbed recently by excessive digging or rotovating then using mycorrhizal fungi will help to reestablish their presence in the soil.

When To Use It

It is not practical to use an additive like this when planting everything you put in the garden. It would also be expensive and overkill in most situations.

I would suggest you only use mycorrhizal fungi when putting in certain plants that are going to get the most benefit by getting a root development head start:

  • Roses
  • Fruiting Plants
  • Trees
  • Shrubs
  • Hedges

In general large, woody plants that and are going to suffer if they do not establish quickly.

These kinds of plants are expensive to buy, require plenty of soil preparation that is going to disturb existing mycorrhizal fungi and can be fussy after transplanting. Using an additive like mycorrhizal fungi is going to benefit these plants.

How To Use Mycorrhizal Fungi

To use it is quite simple, the fungi needs to be in contact with the roots of the plant just before being planted. 

Ensure the roots are moist before planting and hold the plant over the hole where it is going to be placed.

Sprinkle the powder liberally over the roots and it will adhere to the roots because of the moisture. I light dusting is all that is necessary and the excess will powder will simply fall into the hole.

The plant can then be dropped into the hole an backfilled with soil. Watering in as usual and the mycorrhizal fungi will begin in to form a matter of weeks helping the plant establish much sooner.

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