I’ll be honest: when I first heard about mycorrhizal fungi products, I was sceptical. It sounded like another gardening gimmick.

My instinct was that if you planted a good tree into decent ground and gave it the right care in the first season, that should be enough. The trunk, the leaves, the shape of the canopy — I was focused on what I could see. Then I started reading the research, and my position shifted faster than I expected.

The underground partnership between tree roots and mycorrhizal fungi turns out to be one of the most well-documented phenomena in plant biology. And there is a simple, proven way to establish it at planting time: Empathy Rootgrow™.

Here’s the science that converted me, and why I’ve now started to use it on trees we grow and sell.

A 400 Million Year Old Partnership

Mycorrhizal fungi form a natural relationship with tree roots. The fungi attach to the root system and extend fine fungal threads far beyond where the roots themselves can reach. In effect, they build the tree a massive secondary root system.

This relationship developed over 400 million years ago and roughly 90% of land plants form these partnerships. In many ecosystems, the fungi contribute as much as 40% of a tree’s nutrient uptake.

In an established woodland, these fungi are already present in the soil. Young trees plug into an existing network.

A suburban garden is different. Soil that has been built on, compacted, or cultivated for years often lacks the right fungal populations. Your new tree starts alone.

That’s the gap Rootgrow fills.

What the Evidence Shows

I back my planting decisions with data, and the research on mycorrhizal inoculation is consistent.

Faster establishment. Young trees inoculated with appropriate mycorrhizal fungi can establish faster than non-inoculated trees in the first few years after planting. Those early years determine whether a tree thrives for decades or struggles from the start.

Drought resilience. Trees with robust mycorrhizal associations required up to 40% less irrigation to maintain healthy growth. With drier summers becoming normal across the UK, this matters for every garden planting.

Survival rates. In one large-scale programme in Kent, over 25,000 native trees were planted on 40 acres of ex-farmland. Over 98% of the trees planted with Rootgrow survived, compared with around 80% for trees planted without. 

Better nutrition. Phosphorus acquisition improves by 100 to 1000% in mycorrhizal trees compared with those lacking fungal partners. You see the result above ground as stronger growth and healthier foliage.  In the same programme in Kent, trees planted with Rootgrow had twice the girth of trees planted without after 7 years. 

Why Empathy Rootgrow Specifically

I’m selective about what goes into and around our trees. We grow peat-free, harvest rainwater, and run the nursery off-grid. Any product we recommend has to meet the same standard of evidence and integrity.

Rootgrow meets it. It is the first and currently the only plant or soil treatment licensed by the Royal Horticultural Society. Colin Crosbie, Curator of RHS Garden Wisley, has stated:

“At RHS Garden Wisley, we use Rootgrow mycorrhizal fungi when planting trees and shrubs and we are now starting to use it when planting perennials. For me, using Rootgrow mycorrhizal fungi has become one of the most important ingredients to ensure planting success.”
— Colin Crosbie, Curator, RHS Garden Wisley

Field trials with Kent County Council showed clear visible differences in growth and plant health between trees planted with and without Rootgrow, in real-world conditions rather than a laboratory.

Two practical points stand out for me.

First, a single application supports the plant for its entire lifetime. You apply it once, at planting, when the roots are exposed and the cost is a few pounds. The partnership then compounds for decades.

Second, it starts working quickly. Under normal conditions the fungi begin benefiting the plant within 2 to 4 weeks of attaching to the root system.

Less Fertiliser, Less Watering, Better Soil

The environmental case aligns with the practical one, which is exactly how I think a garden decision should work.

Because the fungal network unlocks soil-bound nutrients naturally, treated plants need less synthetic fertiliser. Growers report reducing fertiliser use by 10 to 50% depending on plant type.

The fungi also adapt to your soil. In clay soils they unlock nutrients and act like a clay breaker. In poor sandy soils they seek out scarce nutrients and hold onto water. Whatever ground you’re planting into, the biology adjusts.

For you, that means fewer inputs, less watering through dry spells, and a tree with a genuinely better chance of the long life you planted it for.

How to Use It When You Plant

Application takes seconds. Here’s the method I use with every tree that leaves our nursery:

• Dig your planting hole to the right depth for the rootball.

• Sprinkle the Rootgrow granules directly into the bottom of the hole.

• Place the tree so the roots make direct contact with the granules. This contact is essential. The fungi need to touch the roots to colonise them.

• Backfill, firm gently, water well, and stake if needed.

One application. No repeat treatments. The fungi grow with the roots from that point on.

My View from the Nursery

I came to Rootgrow as a sceptic. I left the research convinced. The data on establishment rates, phosphorus uptake, drought resilience, and real-world survival in hostile conditions isn’t marginal. It’s the kind of evidence that changes how you do things. Once I understood what was actually happening underground, the question stopped being “is this worth it” and became “why would you plant without it.”

People plant trees for the long term. For shade in twenty years, for blossom their grandchildren will see, for a memorial that outlasts them. A decision made on that timescale deserves the best possible start.

Mycorrhizal fungi give the tree that start, quietly, underground, for the cost of a coffee. The evidence is robust, the RHS endorses it, and I’ve seen the difference in establishment across our own stock. My scepticism didn’t survive contact with the science.

If you’re planting this season, add Rootgrow to the hole. Your tree will spend the next fifty years proving it was worth it. And if you’d like advice on which tree suits your space, get in touch. We’re here to help.