Dynamic accumulators, like comfrey, have become a hot topic. These plants are reported to have extraordinary powers to absorb more minerals than the average plant. This makes them very useful if you are trying to make nutrient dense compost for your garden.
Imagine how great it would be if you could grow a plant that increases the nutrients you are lacking in the garden. That is precisely what people are doing with dynamic accumulator plants – or at least that is what is being claimed.
In this post I will examine the idea of accumulator plants and try to figure out what they are. Do they exist? In a future post I’ll ask the question, how can they be used in the garden? Do they add any real value?
Dynamic Accumulators, What are They?
Let’s start with a definition. Wikipedia (ref 1) says the following:
“Dynamic accumulators are plants that gather certain micronutrients, macronutrients, or minerals and store them in their leaves.”
There are a few key points here. First, they are plants – good thing since this is a gardening blog.
These plants gather nutrients, but the type of nutrients are not specified. The amounts that are gathered are also not specified.
The gathered nutrients are then stored in the leaves.
Given this definition, almost every plant is a dynamic accumulator since they absorb nutrients and store some of them in the leaves. An exception would be the leafless orchid. This does not seem like a very useful definition.
The Permaculture Research Institute (ref 2) defines dynamic accumulators this way:
“plants (often deep-rooted ones) will draw up nutrients from the lower layers of the soil, and these nutrients will be stored in the plants’ leaves.“
Any nutrient in any amount qualifies, provided that it is taken from the lower levels of soil – whatever that means. Is 3 inches deep a lower level? Does it need to be 6 inches deep? Is it subsoil? This definition is also not very useful.
What is very surprising is that I was not able to find a better definition. Several other authors (ref 2 and 3) have also looked for a definition and the origin of the term. They concluded that “there are many definitions, all similar, and all fairly vague”, (ref 3). I Also checked Google Scholar for scientific papers on the topic and it seems scientists do not use the term.
The term ‘dynamic accumulator’ is used mostly by permaculturists and they tend not to define their terms and ideas. The whole permaculture ‘thing’ is a very squishy, non-scientific, affair where undefined terms are common – maybe even prefered.
By definition, dynamic accumulators are what you want them to be.
As an aside, the terms biodynamic accumulator and dynamic nutrient accumulator seem to be the same as dynamic accumulator.
Origin of the Term Dynamic Accumulators
Maybe the origin of the term will shed some light on our understanding?
Even this seems to be a mystery. The Permaculture Research Institute (ref 2) suggests that the term might have been started by Robert Kourik who, in his book Designing and Maintaining Your Edible Landscape—Naturally presented a list of dynamic accumulators.
If this was not the first use of the term, Robert Kourik certainly popularized the term by making the list of dynamic accumulators available. The list has been copied many times, with some modifications, and forms the basis of the current lists found on the internet.
This is what Robert had to say recently on The Garden Professors Facebook Group; “Most accumulator lists originated with the 2-page list in my 1986 book Designing Your Edible Landscape Naturally. I no longer believe that list is useful“.
New Definition for Dynamic Accumulators
Since there is no good definition for dynamic accumulators, lets create one.
A dynamic accumulator is a plant that will absorb and retain, in the leaf, at least one nutrient at levels that are at least 10 times higher than the average plant.
Where did the ’10 times’ value come from? I just pulled it out of the air. Without some value the definition becomes useless. Given the variability between plants and soils, a ten times factor seems reasonable.
Some might argue that an important point is missing from this definition since it does not talk about where the nutrients are gathered. Many people believe that dynamic accumulators have high levels of nutrients because they have deep roots. The deep root gives the plant access to extra nutrients. I’ll discuss this in a future post, but the idea that higher nutrient levels are the result of deep roots is mostly a myth.
Do Dynamic Accumulators Exist?
Given the established definition the answer is yes – any plant fits the bill.
What if we use the new definition? The answer is still yes, but not all plants qualify.
There has been quite a bit of work done on hyperaccumulators and phytoaccumulators. These are plants that remove specific pollutants, such as heavy metals, from soil. Specific plants have been identified that are particularly good at absorbing things like lead, or chromium. Once the metals are in the leaf of the plant, the plant can be removed from the site, reducing the contamination in the soil.
A hyeraccumulator is defined as “a plant that can accumulate: 1000 mg/kg of Cu, Co, Cr, Ni and Pb, or 10000 mg/kg of Fe, Mn and Zn in their shoot dry matter” (ref 4).
This is interesting but does it really help gardeners? Are there plants that will accumulate the nutrients plants want? More importantly, can dynamic accumulators be used to improve the growth of other plants in the garden? Does it make sense to grow accumulators? These are good questions that I will tackle in a future post.
- Dynamic Accumulator; https://en.wikipedia.org/wiki/Dynamic_accumulator
- The Facts About Dynamic Accumulators; http://permaculturenews.org/2015/04/10/the-facts-about-dynamic-accumulators/
- What Is A Dynamic Accumulator?; https://palmettopermaculture.wordpress.com/2014/08/16/what-is-a-dynamic-accumulator/
- Accumulation of Pb, Zn, Cu and Fe in Plants; ijagcs.com/wp-content/uploads/2013/03/426-432.pdf
- Photo source: Ling