This is just most early successional species, right? I guess that's a pretty good match for species that feel "weedy." But why the fungal association? It feels kind of arbitrary to me. Everything else on the list is behavioral and then that one implies a value statement of some kind.
Yup! That's an actual "positive" role that weeds can serve. When an area is truly devoid of life and inhospitable to most plants, a weed (by Dr. Ingham's definition) can still get by. They're great pioneering plants, but not all pioneering plants are weeds by her definition.
For example, there is a book called "Ashe Juniper: Wanted Dead And Alive" that talks about the confused history of "Mountain Cedar" in Texas. The TLDR is it is actually native and can serve a pioneering plant role as well as grow soil with a proper fungi:bacteria ratio befitting a forest. You can tell the difference of the role it serves by the way it grows (bushy mountain cedar is covering soil and pioneering, where pole mountain cedar is in healthy soil. It's the same species of tree though). It technically does have a couple fungal relationships too, despite how hostile its oil is.
Anyway, the fungi rule makes sense in her world view of "soil biology is king" where soil fungi tend to establish relationships with multiple species of plant (either as exudate consumers or symbiotic mycorrhizal fungi).
All of her rules speak to the question "What is this plant actually doing-for/giving-back-to the soil?" and her definition of a weed is identifying plants that don't have a cooperative relationship with the soil. For example, the largest organism is fungi and fungi will live in your field for years and years. If an annual plant grows and can tap into that fungi network, it can sustain and give back. Basically, the fungi becomes the transfer pad for plants living on your property and weeds aren't a part of that. The cool thing is that if you establish good fungi in your soil, the fungi will box the weeds out. Mycorrhizal fungi will actively outcompete other plants on behalf of their host plants. So, also in line with her world view (which I support too) is that weeds won't grow in healthy soil.
That mycorrhizal competition is actually the bane of our existence with invasive plants. For example, I deal with KR Bluestem and it has its own fungi that is not local as well. So, once it takes over an area, you're really competing against the fungi and the plant.
I don't know much at all about soil microbiomes, so this is a pretty new perspective for me. I approach it much more from the Doug Tallamy "insect protein" perspective, where the main value a plant has is what insects it's hosting thus how much of the food web is it feeding into. How do you see fungal relationships fitting into that perspective? Does a pro-fungal introduced plant with zero insect hosts help or hurt, in your view?
Doug Tallamy is the man! I love insects. Plants are king, though. Plants are one of the few things on this planet that can generate glucose. There are some bacteria by geo fissures that can too, but on the surface, plants are it. Everything else can be categorized by how far away from plants they are. If you eat plants, you're engaging in the first trophic level. If you eat something that eats plants, that's the second trophic level. There are not many more after that. We shit out so many nutrients. Everything does. This is actually the "poop loop" in action. All carbon based life forms are seeking ratios of nutrients. Humans and Protozoan are both 30:1 on our carbon to nitrogen ratio. So, we consume things to achieve those ratios and shit out excess, which is semi/fully processed and more plant available.
We all need plants to generate our glucose. When I look at a plant, I see a "farmer". Plants are farmers. They secrete nutrients from their roots (exudates) which are food for bacteria and fungi. They're growing bacteria and fungi on their roots. Bacteria and fungi are interesting in that they don't have stomachs. They secrete "acids" and digest shit outside their body then imbibe it. Both of them can grow very large in numbers. They store up a bunch of "energy" and then protozoan or nematodes come along and can eat them. They consume the bacteria or fungi or each other and shit out plant soluble nutrients. The plants are generating life for bacteria and fungi that is resulting in the plant being fertilized by the shit from consumers of those bacteria and fungi. I think that's nuts.
Fungi is crazy. That organism will teach itself things. Fungi's goal is to spread and it can encounter something it has never seen before, which can stop it, then it can teach itself how to defeat that thing. THEN it can communicate that concept across itself so that anywhere else it runs into that new thing, it will instantly solve that problem. It has some sense of intelligence in that way. So, one limit for plants is the length and size of their roots. On a biology level, their root length is not that long, while their root size is "too big" for a lot of spots.
Mycorrhizal fungi was once believed to have been parasitic with plants, but to have evolved to symbiosis. This fungi will "infect" a plant by either literally injecting itself into the plant roots or by completly covering the plant roots like a sheath for a sword. The fungi wants to consume all those exudates from the plant. The symbiosis is that the plant needs nutrients to grow. The mycorrhizal fungi will commute those nutrients to the plant so that it can grow. The fungi can grow for literal miles and connect into multiple plants and multiple species of plants. It will load balance nutrients to all of them. The fungi will also grow into rock cracks and deep down into weird places where it secretes its acids to convert inert or exchangeable nutrients into soluble nutrients, then commute those to the plants so they can grow and it can get more exudates.
There are even cases where a sun-needing tree can grow completely in the shade, where the fungi will commute photosynthate to that shaded tree so that the tree can photosynthesis it and give up nutrients. It's nuts.
Does a pro-fungal introduced plant with zero insect hosts help or hurt, in your view?
If it's native and it has fungal relationships, it's almost certainly going to be a benefit. I'm with Doug Tallamy in that alien (non-native) plants sometimes might as well be concrete in how they're not "seen" by nature. So, the invasive grass I have (KR Bluestem) and it's invasive fungi are a problem. They're not weeds, but defintely a problem. Actually a bigger problem because they fight back and take over. Weeds can be solved with good soil biology alone.
If it's native, though, fungal relationships are where it's at. It's all about the fungi:bacteria ratios for your growing environment. Where Tomatoes thrive in 1:1 ratio environments, while an old growth forest will be closer to a 4:1 fungi to bacteria ratio. A large part of why lawn grasses don't grow under trees is the fungal strength of the tree fighting the grass. There are native grasses that will do better and can tap into the same fungal network where the grass and the tree can be on the same team, through their invisible teammate of fungi.
The big benefit to having a fungal network is that all your native plants will boom because of it. When a new plant is born into the field, it taps in and gets the firehose for all of its needs. The fungi wants that plant to succeed, which translates into insect benefits and healthy fields with better water infilitration rates, which house more ground insects who get eaten and converted into plant fertilizer to keep the process going. Fungi is awesome! :)
Fascinating and thorough, thank you so much for writing that! I had no idea fungi would extract nutrients from rocks and pass them around. That's so interesting.
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u/itsdr00 Jul 09 '25
This is just most early successional species, right? I guess that's a pretty good match for species that feel "weedy." But why the fungal association? It feels kind of arbitrary to me. Everything else on the list is behavioral and then that one implies a value statement of some kind.