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Claim check

Do mother trees feed their own seedlings through the fungal network?

Disputed

Specialists actively disagree, and the disagreement is substantive.

Carbon does move between trees through fungal connections — that much is measured. That a large tree recognises its own seedlings and provisions them is not established, and a 2023 review found the claim being cited far more confidently than the underlying data support.

The claim as it circulates

“Large old "mother trees" recognise their own offspring and send them food through fungal networks.”

Where you may have met it: Bestselling popular books about forests; A widely watched documentary series and its associated talks; Newspaper features about forest cooperation

Taking it apart

What was claimed
That large old trees identify their own offspring among nearby seedlings and preferentially send them carbon and nutrients through shared mycorrhizal networks, in a way that constitutes parental care.
What was actually observed
Isotope labelling has repeatedly shown carbon moving from one tree into the roots of another where fungal connections exist, including between different species in a mature forest. A smaller number of studies report kin-related differences in seedling performance or in network structure.
What the evidence supports
That trees are physically connected below ground by fungal networks; that carbon and nutrients move along those connections; and that the quantities can be substantial in some field experiments.
What it does not support
That the movement is directed, that a donor tree recognises kin, or that recipients benefit measurably. Much of the label recovered from a receiving root sits in the fungus occupying that root rather than in the plant, and separating the two is the central unsolved measurement problem. A systematic review of the field found citations of these results growing more confident over time while the evidence base did not.

Where researchers disagree

This is a live disagreement inside the field rather than between scientists and the public. One body of work, beginning with field isotope experiments in the 1990s, reports substantial transfer and kin-related effects and interprets networks as ecologically important channels. A second body of work argues that net transfer into plant tissue is small, that the fungus is a destination rather than a conduit, and that the field’s conclusions have been amplified by citation practice rather than by data. Both sides are working from real measurements; what they disagree about is what those measurements can distinguish.

The measurement problem is worth understanding, because it explains why a question this attractive has stayed open for thirty years. Label a tree’s canopy with a distinguishable form of carbon, wait, and then find that label in a neighbouring tree’s roots. That result is real and has been reproduced. But a root in a forest is thoroughly occupied by fungus, and the standard method cannot easily tell carbon inside the plant from carbon inside the fungus threaded through it. If the carbon stopped at the fungus, nothing was transferred between trees at all — the fungus was simply paid twice.

The second problem is one of interpretation rather than measurement. Even a demonstrated flow into a recipient plant would not establish provisioning. Resources move down gradients, and a large tree in the light next to a small tree in the shade is a gradient. Getting from "carbon moved" to "a tree fed its child" requires a donor doing something it would not otherwise do, and that step has never been shown.

What remains, after all of that, is still remarkable: the trees in a wood are physically joined below ground by an organism neither of them is, resources move through it, and how much of that matters to anybody is an open scientific question being actively argued. NatureHQ thinks that is a better story than the one in the documentaries.

The evidence, in full

The claims underneath

Each one carries its own evidence, scope and caveats. Expand any of them to reach the studies.

The idea that "mother trees" deliberately feed their own seedlings is not supported by the evidence

Contested

Researchers actively disagree, and the disagreement is substantive.

Systematic and critical reviews find that three widely repeated claims — that common mycorrhizal networks are ubiquitous in forests, that they transfer resources to seedlings in quantities that matter, and that mature trees preferentially supply related seedlings — are not supported by the primary literature, and that citation patterns have amplified positive results.

Who this applies to
the temperate forest systems where the idea originatedDo not extend this beyond the taxa listed — the popular version over-reaches.
Studied in
Pseudotsuga menziesii, Betula papyrifera, Picea abies

You may have heard

“Forests are connected by a wood wide web through which mother trees feed their young.”

The underlying observation — carbon moving between trees below ground — is real. The elaboration into deliberate, kin-directed nurture came from popular books and documentaries rather than from the measurements, and two independent reviews have now found the specific claims unsupported. It is an unusually clear case of a story travelling faster than its evidence.

Why we rate it this way, and what the caveats are
ContestedModerate confidence

Two independent reviews reached similar conclusions, which is significant. They are reviews rather than new data, researchers in the field dispute their framing, and absence of strong evidence is not proof the phenomena are absent.

How far it can be extended

The reviews concern the specific systems the original claims were built from. Extending either the claim or its rebuttal to forests generally would repeat the error being criticised.

Caveats

  • This does not mean fungal networks are fictional, or that carbon does not move between trees.
  • The reviews are literature analyses, not new field measurements.

Where researchers disagree

  • Researchers associated with the original work dispute the reviews' framing and argue that the evidence base is stronger than the reviews allow.
  • Field experiments do detect below-ground carbon movement, so the disagreement is about scale, direction and function rather than about whether anything moves at all.

Still unanswered

  • How common are common mycorrhizal networks in real forests?
  • What experiment could show whether transferred resources actually benefit a receiving seedling?

Last reviewed 2026-08-09

The evidence (3 studies)

When labelled carbon turns up in a neighbouring tree, much of it is sitting in the fungus rather than in the tree.

Contested

Researchers actively disagree, and the disagreement is substantive.

Reanalysis of isotope-labelling experiments found that most label recovered from a receiving plant’s roots was accounted for by fungal tissue occupying those roots rather than by carbon incorporated into plant tissue, and that net transfer into recipient plants, where resolvable, was small relative to the recipient’s own carbon budget.

Who this applies to
Isotope-tracing experiments on plant-to-plant carbon movement through shared fungal networks.Do not extend this beyond the taxa listed — the popular version over-reaches.
Studied in
Glomeromycota, Tracheophyta

You may have heard

“Trees share food through the wood wide web.”

Carbon does move along fungal connections. Whether it arrives in the neighbouring tree, in what quantity, and whether the neighbour is any better off are separate questions — and the measurement that would answer them struggles to tell carbon inside a root from carbon inside the fungus filling it.

Why we rate it this way, and what the caveats are
ContestedModerate confidence

The measurement problem is real and has never been fully resolved: a label in a root can be in the plant or in the fungus growing through it. Later work using methods that separate the compartments better has reached a range of conclusions, and a 2023 review found the citation record running well ahead of the underlying data.

How far it can be extended

Some ectomycorrhizal systems have since reported larger fluxes, and the magnitude remains disputed rather than settled in either direction.

Caveats

  • That carbon moves through the network is not in dispute. What is disputed is how much reaches plant tissue and whether it matters to the recipient.
  • A quantity too small to affect a mature tree may still matter to a seedling in deep shade.

Where researchers disagree

  • Field labelling of mature trees has recovered substantial quantities of label in neighbours, while reanalyses of pot experiments conclude that net transfer into plant tissue is minimal — and the two are hard to compare because the methods resolve the plant–fungus boundary differently.
  • Whether the fungus should be treated as an intermediary or as a destination is itself unsettled, and it changes what "transfer between trees" means.

Still unanswered

  • How much transferred carbon is incorporated into recipient plant tissue under field conditions.
  • Whether transfer is ever large enough to affect the survival or growth of the receiving plant.

Last reviewed 2026-08-30

The evidence (4 studies)

Carbon does move between trees below ground

Well supported

Good evidence backs this, though some details remain open.

Isotope-labelling experiments in the field have detected movement of carbon between trees of different species, including between mature trees, with mycorrhizal fungi the most likely route.

Who this applies to
the temperate forest tree species tested so far
Studied in
Betula papyrifera, Pseudotsuga menziesii, Picea abies, Fagus sylvatica
Why we rate it this way, and what the caveats are
Well supportedModerate confidence

That carbon moves is well evidenced by two independent field experiments. What is far less certain is how much, by which route, and whether the receiving tree benefits at all.

How far it can be extended

Detected independently in North American and European forests, in seedlings and in mature trees, using different labelling approaches.

Caveats

  • Carbon found in a neighbour's roots may have been used by the fungi rather than by the tree.
  • Net transfers measured were small relative to a tree's total carbon budget.
  • Labelling designs struggle to exclude movement through soil rather than through fungi.

Still unanswered

  • How much of the transferred carbon is actually used by the receiving tree?
  • Is the fungus a conduit, a trader, or the main beneficiary?

Last reviewed 2026-08-09

The evidence (2 studies)

Go deeper

Mycorrhizal networks

The fungi are real, the connections are real, and carbon does move. Whether anybody is sharing is a different question, and it is still open.

Related things people ask

Last reviewed 2026-08-30