Fertilizer Garden Myths

Robert Pavlis

A lot of the stuff on the internet is garbage when it comes to gardening advice. I am not surprised about that since many people just repeat what they have heard and give it very little thought. Some garden writers don’t actually do much gardening – they are writers, not gardeners. I rarely believe information unless it comes from experts in a field, government sites or published research articles.

This post is about an information guideline on fertilizers and soil amendments which is published by a government source – one you should be able to trust. Unfortunately it is full of incorrect or misleading advice. Let’s have a look at some fertilizer gardening myths.

fertilizer garden myths; Lobelia cardinalis X Lobelia siphilitica, by Robert Pavlis
Lobelia cardinalis X Lobelia siphilitica, grows just fine without added fertilizer, by Robert Pavlis

Fertilizer Garden Myths

The goal of this post is not to provide an extensive list of myths about fertilizers, nor is the goal to provide a detailed discussion of some specific myths. My goal in this post is to review a published guideline by the University of Maryland Extension office. This guideline, called ‘Soil Amendments and Fertilizers’ is all about fertilizers and was written specifically for the home gardener (ref 1).

Unless stated otherwise, the statements in quotes are taken from reference 1.

Balanced Fertilizer

“A fertilizer containing all three nutrients (N, P and K) is a balanced fertilizer.”

That statement is just wrong. A balanced fertilizer contains the same amounts of N, P and K. For example a 10-10-10 fertilizer is a balanced fertilizer and a 10-5-5 is not. For more information on this see Fertilizer Nonsence #1: Balanced Fertilizer and Fertilizer NPK Ratios – What Do They Really Mean?

Soil Science for Gardeners book by Robert Pavlis

Starter Fertilizer

Starter fertilizer specifically formulated for seedlings and transplants , are high in phosphorus to foster root establishment.

It is true that so called ‘start fertilizers’ and ‘booster fertilizers’ are higher in phosphorus, but it is incorrect to promote the idea that adding extra phosphorus will foster root establishment. Most garden soil has lots of phosphorus in which case adding more does nothing except cause pollution – if enough is added it will even become toxic to the fungi in soil. Adding phosphorus does not promote root growth, unless the soil has a deficiency. But that is true of any nutrient. If any nutrient is deficient, and you add it, it will foster root growth. There is nothing magical about phosphorus.

Ammonium Sulfate Fertilizer

“Ammonium sulfate, a dry fertilizer, …. is very acidic. ”

Any dry fertilizer is not going to be acidic. It would need to be dissolved in water to become acidic. At a 0.1M solution ammonium sulfate does have a pH of 5.5, which I don’t consider ‘very acidic’ when compared to vinegar at pH 2.4. It is also less acidic than the preferred soil pH for blueberries which is 4.8 to 5.5.

Bone Meal for Bulbs and Root Crops

“bone meal is especially good for bulbs and root crops, and lasts for 6 to 12 months.”

Bone meal has been discussed in Bone Meal Organic Fertilizer . It contains phosphorus and calcium – most garden soils are not deficient in either of these nutrients. High levels of phosphorus are not needed for growing bulbs.

Bone meal releases the phosphorus very slowly, and once released it moves through the soil very slowly at about an inch a year. It will be available to plants for many years – not 6 to 12 months. Bone meal should not be used unless a soil test shows a deficiency of either phosphorus or calcium, and in that case there are better options for providing either nutrient.

To better understand how phosphorus affects soil, see Rock Phosphate Fertilizer.

Compost Tea

“Compost tea is a good method of applying soluble nutrients to foliage and roots in the early part of the growing season when nutrients from soil organic matter are not yet available. Do not use farm animal manure compost.”

There is no good scientific evidence that compost tea is any better than just using compost. For more details see Compost Tea.

Building Natural Ponds book, by Robert Pavlis

The statement ‘nutrients from soil organic matter are not yet available’ is interesting. It is true that in early spring when the soil is still cold, decomposition of organic matter would be slow, but nutrients resulting from decomposition in prior years would be available.

The recommendation not to use animal manure composts for making tea goes against most suggestions for making compost tea. Once the manure is composted it is not chemically different from other types of compost. Some people even prefer to make manure tea using fresh animal manure.

Foliar Fertilizers

” Plants take up nutrients more efficiently through leaves than through roots.”

At first glance this makes no sense. Leaves aren’t really designed to absorb nutrients. On further reflection I think it depends on how you define efficiency. Nutrients sprayed on leaves enter the stomata easily. I guess you could call that efficient. The problem is that most of the sprayed nutrient will stick to the leaf surface until the next rain or run off the leaf as it is being sprayed. That is not efficient.

Some nutrients do not move easily once inside the leaves so they don’t get to where they are needed eg iron, manganese and calcium. When calcium entering a leaf it will not be transported to developing fruits so it won’t prevent blossom end rot (BER) in tomatoes. Calcium entering roots can prevent BER. More on BER can be found in Blossom End Rot.

Foliar feeding for the home gardener is not recommended. It is of value in specific farming applications, but the process is too complex for a home gardener. For the long term feeding of plants it is less effective than putting fertilizer on the soil.

Humates and Humic Acid

“Humates are thoroughly decayed … so nutrients are available to plants. Contains up to 35% humic acid.”

The first part of the statement is correct- Humates are thoroughly decayed. What this means is that all of the nutrients that can be extracted, have been extracted, so nutrients are NO longer available to plants.

Adding humates have shown to have little effect on plant growth. Reference 6 reviewed many studies looking at the effect of humates and humic acid on turf grass and found no benefits. They do improve soil and act as a sponge to hold nutrients from other sources similar to most organic matter. Roots can then access these nutrients. The same goes for humic acid. So there may be some long term benefits.

Kelp – Magical Powers

“Kelp is valued as a growth stimulant because of rich concentrations of trace minerals (over 60 types), amino acids, vitamins, and growth hormones. ”

Garden soil is usually not deficient of trace minerals and most plant debris and compost contains them. All organic material contains amino acids – kelp is not unique in this regard. The vitamin B1 which was promoted extensively as a growth stimulant for plants has no effect on plant growth. Some other vitamins may have an effect.

Seaweed extracts have been shown to stimulate plant growth but the exact mechanism for this is not known (ref 2). It is too early in the research process to claim magical powers for kelp. There are also environmental issues if the kelp is harvested from the sea.

Azomite and Rock Dust

“Azomite or rock dust – an aluminum silicate clay mixed with over 50 minerals.”

It would seem to be a great addition to gardens, and it is used in agriculture in some countries. Based on the data I have seen, this material breaks down very slowly – we are talking hundreds of years. It is not considered to be a good fertilizer.

Tomato Blossom End Rot

“Blossom end rot of tomatoes is caused by a lack of calcium in the developing fruit. Prevent it by adding a small handful of finely ground limestone to each planting hole prior to transplanting”.

As explained in Blossom End Rot, the first sentence is correct. BER is due to a lack of calcium in the developing fruit. But this may have nothing to do with the amount of calcium in the soil or even in the plant. Plants can have trouble transporting the calcium in the plant to where it is needed, ie the developing fruit. This can be caused by irregular water levels.

Advising someone to add more calcium without knowing the calcium levels in the soil is bad advice.

Urea Fertilizer

“Urea: Must mix into soil to prevent conversion to ammonia and subsequent escape into the air. ”

Urea is a high nitrogen fertilizer (45,0,0) that is relatively inexpensive. It is true that urea converts to ammonia and if the ammonia is near the surface of the soil, it can escape as a gas into the air. It is not correct to say urea needs to be mixed into soil – although this can be done if you want to disturb the soil and promote weed growth. In permanent landscapes, flower gardens and lawns, it is much better to simply water it in. It is very soluble in water, and is easily washed into the soil. I apply it just before a good rain thereby preventing it from escaping into the air.

Wood Ashes

“Wood ashes contain from 1 to 2% phosphorus and from 4 to 10% potassium and increase soil pH. The recommended yearly application rate is 25-50 lbs/1,000 sq ft. ”

Wood ash does contain phosphorus and potassium. Most garden soil contains enough of both nutrients. You should never apply a fertilizer unless you know it is required. Without a soil test you might already have high levels of potassium or phosphorus and just make the situation worse. Even if you need to add one or the other of these nutrients, wood ash should not be added to soil that is already on the alkaline side. Instead select a fertilizer that will not increase pH.

High Organic Matter is Good For Soil

“Most plants perform best in soils high in organic matter (greater than 2% organic matter by weight).”

Native top soil contains about 5% organic matter, by weight (or 10% by volume). As organic levels get over 8%, by weight, they start to cause problems including nutrient levels that are too high. You can have too much organic matter.

Plants perform best with the right amount of organic matter – not high levels.


“Humus can be purchased.”

I have discussed humus before in What is Humus? It is true that most organic matter, like manure and compost, contain some minor level of humus, but except for this, I have never seen ‘real’ humus for sale. I have seen a lot of bogus marketing which claims their product is humus, but all that means is that they are using the term incorrectly – referring to anything organic as being humus.

Use Manures Wisely

“Apply uncomposted manure in fall only. Mix into the top 4-6 inches of soil. Don’t leave it on top of the ground.”

Adding manure to the garden is a great idea, and adding fresh manure can burn plants. However, old manure that is still uncomposted can be added directly to the garden and one of the best ways to do this is to leave it on the ground. That way it continues to decompose and add nutrients for plants without burning roots.

Digging manure into soil is not a good idea. It brings weed seeds to the surface allowing them to germinate. The digging also destroys soil structure. Add the organic matter to the surface and let nature add it to the soil.

Mushroom Compost

“Mushroom compost can have high soluble salt levels and should be fully incorporated and watered prior to planting. ”

It is true that most mushroom compost contains high levels of salt – that is why it is not recommended for gardens, except in very small amounts.

Watering may remove some of the salts, but only the soluble ones. The problem with this recommendation is that watering will also leach out the good nutrients, in particular nitrogen. It makes no sense to me to add a product that has too much salt, and then try to wash away the salts. Why not just use a better organic source that does not have high salt levels?

Sand Added To Soil

” To improve water drainage and aeration of clay soils you need to add a minimum of 50% sand by volume.”

Adding sand to clay soil is a complex issue that needs  a separate blog post. Some experts, mostly on the western half of the US claim that adding sand to clay soil will create a hard substance like concrete. Other experts, in the UK, Europe, and Canada (me) routinely recommend adding sand to clay.

In this post I won’t argue for or against adding sand, except to say it works for me. However, the idea that you need to add at least 50% sand is ridiculous. The formulas for several soil properties change linearly with the amount of sand in the soil. Any amount added will start to change the properties of soil. I’ll provide details in a future post.


“Bioactivators: various commercial products containing: bacteria, growth hormones, nutrients, and vitamins may be useful as a tonic for lawns, seedlings, transplants and plants languishing in cool soils in the spring”.

Adding nutrients will help, provided the soil has a deficiency. Adding bacteria and vitamins does not help plants except in some special cases. For example, nitrogen fixing bacteria on pea seeds does work. Do growth hormones work? They probably have some effect, but they have not been shown to be needed for garden situations.

Don’t bother with bioactivators.

Lowering Soil pH With Sulfur

“At a pH above 6.0, iron sulfate lowers pH more quickly than sulfur”.

Sulfur is the go-to product for lowering pH in soil, so I found this statement to be a surprise. Since it is the sulfur molecule that bacteria convert to sulfuric acid which in turn causes a drop in pH, I would expect you need less pure sulfur than iron sulfate to cause the same change in pH – why buy iron and oxygen molecules if you don’t need them?

A little Googling and I found that the University of Illinois Extension (ref 3), Purdue Extension (ref 4) and Colorado State University (ref 5) all disagree with the quote. In fact, you need 6 times as much iron sulfate as sulfur to cause the same pH drop.

High Levels of Nutrients

“Nutrient levels are often in the ‘excessive’ range in older and well-tended landscapes. This is not a problem for plants.”

What are they saying here? High levels of nutrients don’t bother plants? If that is the case why does the same article say the following in the Boron section; “Can be toxic to plants if applied in excess?”

High levels of nutrients become toxic to plants. That is why you should not add fertilizers unless you know the soil needs them and you should not add excessive amounts of organic matter for the same reason. Too much nutrient is bad for plants.

Soil pH Levels

” Pay close attention to your soil pH readings and be prepared to adjust them according to your soil test”.

The suggestion is valid if you have very high (over 7.8) or very low (below4) pH. If you are inside of these extremes it is better to accept your soil pH and plant things that will do well in your soil. Changing soil pH is difficult, requires continual attention and is just not a good idea for home gardeners.

I don’t grow blueberries or azaleas because my pH is 7.4. I have learned to live with that and my life and the life of my plants is better for it.

Before buying a pH tester for home use, read; Soil pH Testers – Are They Accurate?

Fertilizer Garden Myths Conclusion:

Wow – what a list, and I did not even touch on water-absorbing polymers and mycorrhizae. It is no wonder gardeners are confused about what do do in the garden. One would hope that a US university extension office – who is the states expert on such matters – would get it right. Not so in this case.

To be fare, the article discussed here does contain a lot of useful information. It is too bad that the good is mixed in with the bad and the very bad. The average home owner will not know which is which.

Most other university extension articles are quite good and I trust them, most of the time!


  1. Soil Amendments and Fertilizers, by University of Maryland Extension
  2. Seaweed Extracts as Biostimulants of Plant Growth and Development: Seaweed Extracts as Biostimulants of Plant Growth and Development
  3. How to Lower Soil pH: https://web.extension.illinois.edu/cfiv/homeowners/080818.html
  4. Lowering Soil pH for Horticulture Crops: Purdue University
  5. Soil pH: http://www.ext.colostate.edu/mg/gardennotes/222.html
  6. Humate and Humic Acid: http://aggie-horticulture.tamu.edu/newsletters/hortupdate/hortupdate_archives/2002/jun02/art4jun.html
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Robert Pavlis

I have been gardening my whole life and have a science background. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

31 thoughts on “Fertilizer Garden Myths”

  1. When I did a google search for “azimite research” several studies came up that seem to indicate that azomite has substantial benefits for some crops. I’m not an expert so I’m just wondering what you think of studies like
    https://www.researchgate.net/publication/317339057_Evaluation_of_the_effect_of_Azomite_fertilizer_on_the_growth_and_some_physiological_traits_of_two_tomato_Lycopersicun_esculentum_cultivars_under_drought_stress and https://azomite.com/pepper-study/

    • The first paper does not show that ” azomite has substantial benefits for some crops” – it shows there are some benefits in two cultivars of drought stressed tomatoes. And the study was a pot study – not a field study. These generally do not involve normal soil. It tells us very little about what happens in the field, especially in a garden that is usually irrigated.

      The second study showed some increase in weight of tomatoes with 100 lb application, but not at the 200 lb rate, and then only for one of the two cultivars tested. There was no data for the change in nutrient levels in the soil. This is published by azomite. I cannot find this study published in a scientific journal – so not peer reviewed and therefore not of much value.

    • Do they really use as a fertilizer on farms? – yes
      Do they use bloodmeal – not usually – far too expensive
      Do they use bonemeal – maybe it is cheap and organic certified (I believe)

  2. So the long and short of it is you recommend spreading compost and not bothering with anything else? Although you state you use urea–when and why?

  3. Hi, I appreciate your scientific research and information,and would like some help if possible. What reasonably natural amendment would you recommend for extremely alkaline soil, and also with alkaline well water for watering?
    While lilacs,locusts, linden trees, mullen and cornflowers will grow, almost everything else slowly dies ( short season, cold winds and herbicide drift from nearby farms don’t help either). From your article, maybe kelp? Blood meal? I’d prefer not to do sulfate since it is very easy to get it wrong? I’m not looking to plant blueberries, but being able to keep some vegetable plants going would be nice, also help for the hardly apple trees and hardy roses that cant take the soil either.
    Thank you

    • You did not say what “extremely alkaline” soil is. Could the problem be something else like natural LIME in the soil?

      I’d talk to more experienced gardeners in the area to better understand the soil.

      If the soil really can’t grow more things, then you might need to use raised beds with plastic in the bottom.

  4. In Jersey, traditionally farmers used to gather seaweed (known as Vraic in the Jerriais language) Two carefully regulated Vraic harvests were held every year in February and June.

    The main use of vraic is for spreading over potato fields during the winter. It is then ploughed into the soil before the potatoes are planted in late winter and spring. Vraic was traditionally gathered by horse and cart in Grouville Bay and St Ouen’s Bay and the practice continues using tractors and trailers, although the quantity taken has diminished over the years.

    I’d be interested in your comments on how this would work. It was done for centuries, although the advent of chemical fertilizers has largely replaced it.

    It would seem that vraic decayed into the soil more slowly than chemicals as one of the problems we face is blooms of sea lettuce, green across the sand of bays, which appears to feed from nitrate run-off fields.

    • Seaweed is organic and as such it decomposes and slowly releases nutrients. This is true of any plant or animal material used. Ploughing it in is not good for soil structure and many people have moved to no-till farming.

      The problem with fertilizer is that the nitrogen in it is very soluble and easily runs into waterways. Once there it helps plants grow. Over a longer period of time, phosphate also contributes to this problem. Phosphate moves through soil much more slowly than nitrogen.

      There is nothing wrong with using fertilizer – if it is used in correct amounts. In an effort to maximize yield, many over use it, resulting in excess ending up in lakes and the ocean. The same problem exists if too much organic matter is used.

  5. yo Robert! I have been reading a couple of your articles and got to thinking whether nitrogen fixing plants are good to grow close by to later cut and drop them near your fruiting plants for the extra nutrients. what would you recommend to the general gardener?

    • There are a couple of myths about nitrogen fixing plants. While they grow they add very little nitrogen to the soil – the nitrogen produced is used by them to grow. Most of the nitrogen ends up in the seeds. If you grow a legume to seed state, there is little nitrogen in the leaves.

      Harvesting the green leaves will add nitrogen to the soil as they decompose. Some people grow the plants right beside the fruits, especially a row of fruiting trees. Clover is also grown in grass and as it is mowed it adds nitrogen to the lawn.

      Any of the beans or peas would be good crops to grow, produce lots of green matter and are easy to harvest.

  6. So ideally we should grow a companion plant with our crop plant that will replace what the crop plant takes away at harvest?

    • At first glance that sounds like a good idea, but in order for the companion plant to provide the nutrients, it must first take them from the soil. So then you need companion plants for your companion plants.

      This does not work in practice except for one case, legumes support microbes that take nitrogen from the air and transfer it to plants in a form they can use. When these are then added to soil, and composted, they do add nitrogen that was not in the soil in the first place.

  7. I commented on your other blog and I asked you about a soil acidifier and after reading this article, I would like to clarify what it is that I am trying to do. I built a small raised bed that I filled with soil from the Georgian Bay area which is where I got the blueberry plants that I would like to grow. I incorporated Sphagnum Peat Moss into this bed which (to my understanding) has a ph of 3.5-4.0. This bed is mulched with pine needles and shredded leaves and I would like to add a bit of soil acidifier to help keep the ph low as I have naturally alkaline soil even though it isn’t in this bed…yet. I have also learned that pine needles do not acidify the soil.
    Any comments or advice would be appreciated.
    Thank you,

    • You are right pine needles do not acidify soil. I also don’t think peat moss will acidify the soil, even though it is acidic. The best way to acidify soil is to add agricultural sulfur or is you are fertilizing, use a sulfate, like potassium sulfate – that is assuming you need to add potassium.

        • Most nurseries sell small boxes of it. I’d try some feed stores and see if you can get larger amounts. It should be quite cheap from the right source, but it is not very common.

  8. Oddly enough, I don’t use any fertilizers ever, but fortunately I do know most of my plants from the Southwestern native habitats and their requirements from over thirty years of successes and failures. I wished I knew then what I know now over 30+ years ago. Just think what one could have accomplished. I dislike plants over one gallon sized from the nursery if I don’t grow my own, because they have always out performed larger one. Mostly it’s a spiraling rooting issue I don’t like. Most commercial landscaping companies and probably homeowners want instant landscape installation in their projects yesterday. The key for me has always been the correct use of mycorrhizae and beneficial bacteria and which work best for whatever plant community I’m designing for. Your point about commercial farming however needing to continue with inputs of fertilizers needs some correction. Many farmers are finding out that they no longer need companies like Dow Agro-Chemical etc. The same basic fundamentals and principles with which Nature supplies nitrogen, etc still aply there as well. I found this video some time back on a farmer named Gabe Brown of North Dakota who through trial and error discovered it is possible, but it takes ongoing ground coverage and mycorrhizal life sustaining cover crops between plantings to do the trick.

    Gabe Brown: Keys To Building a Healthy Soil

    • I searched my post about comments saying that commercial farming requires input of fertilizers, and did not find any?

      I agree that farming can be done, on a limited scale, without using fertilizers. Based on what I have read, there is not enough compost and manure produced in North America to support all of the farming activities. I don’t know if that is true or not. But using only manure has other issues. You can’t selectively add the nutrient you need. In order to add nitrogen you also need to add P and K, which can quickly reach toxic levels.

      A lot of what Gabe Brown says is true – but not everything. Farmers around here practice no-till, and they would love to do more of it, but it does not work for all crops – yet.

      • Robert: “I searched my post about comments saying that commercial farming requires input of fertilizers, and did not find any?”

        Actually it was in your last comment on the post where replied to commenter “Robert Brook”, so I generally read an entire article AND it’s comments section before I make a comment. But I truly agree that urban landscapes in general need no fertilizers if maintained like an ecosystem if that is possible.

        Robert: “I agree that farming can be done, on a limited scale, without using fertilizers. Based on what I have read, there is not enough compost and manure produced in North America to support all of the farming activities.”

        What can be done without the inputs are the vast grain crop farming [corn, wheat, oats, soybean, rice etc etc etc]. An example of where you would have to till would be potatoes. The seed potato is planted in the furrow trench and when foliage is tall enough, the hills between the trenches are disked to partially cover the stems from which new potatoes will grow. The University of Wisconsin and University Maine both did multiple potato studies in several different locations in their respective areas in using Mycorrhizal Applications Inc’s product MycoApply which has several species of fungi and beneficial bacteria. The conventional recommended input of 120lbs per acre of phosphorus was drastically reduced to 30lbs per acre which gave a savings was $81 per acre. The yields were also higher. But manures and other safe organic wastes I believe should always be placed back into the fields. But you can even over do those if not careful.

        Robert: “You can’t selectively add the nutrient you need. In order to add nitrogen you also need to add P and K, which can quickly reach toxic levels.”

        Actually I would never worry about nitrogen. If you have a soil that breathes and percolates wonderfully as a result of healthy microbial communities underground, they will do the nitrogen gathering themselves which is what all plant communities did prior to the introduction of the “1950s Green Revolution”. Nature has been programmed for countless centuries to perform that tasks prior to human industrial age and I understand the business needs of former allied/axis munitions companies to find ways to continue to make money after the war was over, but the over doing it has ruined millions of acres of soil. It also allowed the average farmer to not do their own homework on how nature really works and change their practices. I condemn the so-called Organic side because the reality is, they do not really discuss these things either. Everything with them is manure, breeding and organic versions of pesticide spraying which in truth is no different than the industrial side. I’m not sure what your experience is, but with a mycorrhizal soil system, I get no weeds other than tree and shrub seedlings, maybe the occasional stunted growth of a couple of sow thistles.

        • I agree that in natural areas you don’t need to add nitrogen, but in most agricultural fields you do. Even in home gardens where you remove produce, you usually need to add some nitrogen, either as fertilizer or from an organic source. Nitrogen is the one nutrient that is easily lost to the air, and in water runoff.

          The soil destruction we have is mostly due to cultivation, not the addition of fertilizer. Adding reasonable amounts of fertilizer is not destructive to microbial life.

          Not sure what a ‘mycorrhizal soil system’ is, but any healthy soil will support weed seed, unless the seed is prevented from germinating with something like mulch, or shade.

          • Robert: “I agree that in natural areas you don’t need to add nitrogen, but in most agricultural fields you do.”

            Totally disagree with Agriculture. If you develop a soil system which is more mycorrhizal along with the beneficial bacteria, they create a soil that actually breathes and provides all the nitrogen needed for crops, but you got yo keep multispecies cover crops on the soil. Allow soil between monocrops to lay fallow for too long and you lose the mycorrhizal fungi. They need hosts and this is where modern conventional Ag fails miserably.

            Robert: “Not sure what a ‘mycorrhizal soil system’ is, but any healthy soil will support weed seed, unless the seed is prevented from germinating with something like mulch, or shade.”

            When you have mycorrhizal plants removed from any type of ecosystem you then create nothing but a bacterial one which actually favours weeds and by weeds I am talking Ruderals. Even crops like Canola , plants in the Mustard family, Radish etc are bacterial, not mycorrhizal. My experience is that if you have a health mycorrhizal soil system, the mycorrhizae will outcompete the weeds to available phosphorus. If any do show up they will be stunted in growth and not an issue. I’m actually surprised you didn’t know who Mike Amaranthus was because he along with Dr Don Marx and even Paul Stamets have written many of the early papers on mycorrhizal fungi in the environment from the 1970s & 80s. The video below is Dr Wendy Taheri from South Dakota State University who is a microbiologist who specializes in endomycorrhizae, especially with crops. Here she is teaching farmers eager to learn how to greatly reduce or eliminate entirely all synthetic agricultural inputs. The biggest obstacle is you have a giant industry which will do whatever it takes to fight against this type of change over to safer practices and a system where a farmer doesn’t have to fork over 1000s of dollars a year in synthetic fertilizers or other pesticides. None of these people are the type of target folks which the industry and professors over there from WSU make fun of as Luddites pushing myths, fables and Voodoo science. The woman below is an extremely sharp intelligent woman and I wish there were more Academics like her pushing for a Biomimetic approach as opposed to the majority of Academics pushing the industrial standard.

            CCTA – Wendy Taheri, ARS-SD, talks on Fungi and its utmost importance

          • I don’t agree with your statement “My experience is that if you have a health mycorrhizal soil system, the mycorrhizae will outcompete the weeds to available phosphorus.” Many weeds form mycorrhizal associations and also benefit by their presence. In my natural woods, I still get weeds both herbacious and woody. If your statement were true natural woods would be free of weeds since they have a very healthy fungal population. And then of course there is the question of what is a weed, which is a subjective call and mycorrhizal are not subjective.

          • Robert Pavlis: “I don’t agree with your statement “My experience is that if you have a health mycorrhizal soil system, the mycorrhizae will outcompete the weeds to available phosphorus.” Many weeds form mycorrhizal associations and also benefit by their presence. In my natural woods, I still get weeds both herbacious and woody.”

            Actually many of those mycorrhizal crops benefit from mycorrhizal plants in the fields. Like Hairy Vetch which will outcompete weeds and provide nitrogen to the soils. But most agricultural practices almost completely ruin soil health, not allowing it to breathe and creates idea circumstances for ruderal types weeds which farmers are mostly fighting. Gabe Brown, who you said you weren’t very impressed with has successes with companion planting Field Corn with Hairy Vetch. In such settings the scenario is more of “Survival of the Mutually Cooperative” rather than the failed Darwinian view of “Survival of the Fittest”. So again, I’m NOT talking about WOODS. It’s the industrial agricultural practices like tilling, growing monocultures and dumping high concentrations of chemical applications which discourage Arbuscular Mycorrhizae, but encourage ruderals to thrive, which is why the need for massive amounts of herbicide chemical use these days. But then I’m certain you already have been told this and/or knew this.

            Where I come from originally in Southern California, especially in the old days where winter dryland farming of wheat and oats were everywhere in the hotter interior valleys, these practices encourage almost overwhelming increase of Fiddlenecks to in some extreme cases I witnessed first hand took over 75% of the oat or wheat crops. Another disturbing trend is that many of the modern strains or varieties of Oats, Wheat or other long traditional mycorrhizal rooted crops no longer allow mycorrhizal colonization on their roots since in much of this cross breeding and even genetic manipulation has created a loss of information for instructions for colonization have been silenced in the genetic codes for mycorrhizal colonization for crops to be dependent on Agro-Chemical inputs. So anyone growing now days really have to test a variety of seed to make sure Endo-mycorrhizal fungi will fix to the roots.

            “Robert Pavlis: In my natural woods, I still get weeds both herbacious and woody. If your statement were true natural woods would be free of weeds since they have a very healthy fungal population. And then of course there is the question of what is a weed, which is a subjective call and mycorrhizal are not subjective.”

            I think this is where we are talking past each other. You live in heavily Temperate and Boreal wooded forest areas. I on the other hand come from a region of Mediterranean and Desert Climates of the Southwest. [Mind You, I live in Sweden now) And yet the basic fundamentals and principles are still the same ecosystem with modifications to accomdate ecosystem types. When I speak of weeds, I’m taking strictly Ruderals. A giant beautiful Oak tree [which is mycorrhizal] in the middle of an Iowa cornfield could still be considered a weed by definition. Also I am talking with respect to areas of landscape such as people’s home gardens and industrial agriculture where a rich plethora of various chemicals have mostly discouraged mycorrhizal presence in plants. Then some plants can be mycorrhizal and bacterial (ruderal) depending on the environment, what we otherwise call circumventer plants.

            I’d guess the easiest way of telling a ruderal plant from a circumventor plant is how long it lives and how well it lives within it’s plant community. Ruderals prefer waste areas man has screwed up [urban housing development, roads, railroad right-of-ways, industrial farming, overgrazed pastures, etc], circumventors live much longer within a plant community and are very short lived in areas where many has screwed up. Having said that, a ruderal commonly lives one season and a circumventor will still live for a decade on a screwed up site. And mostly it’s these horrible land management practices that I am referring to. In my mycorrhizal landscapes back in San Diego County, I went down to maybe 2% of ruderal weeds with most being extremely stunted in growth. Most were Fleabane or Sow Thistle. At most maybe I would get half a dozen or less. At worst, I get lots of mycorrhizal shrub and tree seedling popping up very easily in the mycorrhizal beds, but I can deal with those. Funny thing, in my Mum’s dry landscape beds were many Desert and Chaparral plants coexist together, I get riparian species like Sycamore germinating and I only noticed them when I visit and they are a foot or two high. For me that was actually exciting to see because abundance of water in the hot climate wasn’t the factor as much as the seeds where they emerged with tapped into the healthy mycorrhizal grid or network and their needs were easily taken care of.

  9. I have to repeat – Wow! How could a common gardener navigate through this sort of article?
    The sad reality is that most people writing such things probably never grow anything in the garden, same like the ones who write about plants that they have never seen in their whole life. In both cases though, they are considered very ‘knowledgeable’…

    • It is a problem for all hobbies. Experts tend to be the ones who write – not the ones who do. So am I now an expert? 🙂

  10. phew! You are a brave man tackling all that stuff!
    if you go to most gardening articles and websites you get balderdash about fertilisers!
    I don’t understand why so many gardeners are so gullible
    Perhaps your opening statement is the key – in many garden circumstances no extra nutrients are needed! But not all!
    You are a very wise man.

    • Thank you. I think people feel a need to fertilize because they need to eat. If they need to eat – then plants must need to eat too. The other reason is in horticultural fields farmers usually need to fertilize since they are removing crops each year. People don’t understand that in gardens where you don’t remove crops, there is no need to fertilize.


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