By Rachel Foebel, Master Gardener in Training

What are dynamic accumulators?

These are plants known to collect large amounts of soil nutrients, usually from deeper in the soil via long tap roots (sometimes fibrous roots as well) and store them within the plant. These plants are used to then release their nutrients to the upper layers of the soil as the above ground parts of the plant break down, either by harvesting, winter, or completion of a life cycle. The most known and used plants tend to be Common Comfrey (Symphytum officinale) or Russian Comfrey (Symphytum x uplandicum) and sometimes plants from the nettle family such as stinging nettle (Urtica dioica). Additionally, cover crops such as legumes are used widely to serve this same purpose. Dandelions and rhubarb are also known to be dynamic accumulators.

Left: Comfrey picture (caption: Common comfrey (Symphytum officinale)
Right: Comfrey flower (caption: Comfrey flower)

Is there any science to back this up?

While this method of soil improvement has been discussed and used for a while (since the 1980’s), research to prove this concept has only begun to occur very recently.

In 2020, Northeast SARE (Sustainable Agriculture Research and Education) provided a research grant to Unadilla Community Farm, in coordination with Cornell University, “to help expand our collective understanding of what exactly dynamic accumulators are, how they work, and what are some practical applications for these plants,” (Zarro, 2020). For the purposes of their work, a dynamic accumulator was defined as a plant containing roughly 200% of the set average of any of the 20 beneficial nutrients they had data for (Tyler, 2022). They were able to identify over 340 plant species that qualify based on these terms and created a dynamic accumulator online database.

Here is where you can find this database: https://docs.google.com/spreadsheets/d/19S3wsjXU6VPzmbklZLVxKt6DCyZIPjCYw6zRrVg7M4Y/edit?pli=1&gid=1519867200#gid=1519867200

Add picture:

A clip of the database to show how it displays its information about each nutrient

And here is where you can find more information on the methods they used to compile the database: https://smallfarms.cornell.edu/2022/04/new-findings-further-the-study-of-dynamic-accumulators/

The work done since the database was formed has given more insight still. It has been found that these plants cannot perform to the level they are expected on the database unless these nutrients exist somewhere in the soil to begin with. While this seems obvious, it means that you can’t expect these plants to fully restore poor soil on their own. They can only be one part of the plan or be used to maintain soil that already has some nutrients to share.

Are there dynamic accumulators that are native to Ontario?

Yes. Some examples are paw paws, blue cohosh, wild strawberries, self heal. To find more you can cross reference the above-linked dynamic accumulator database with a native plant database like this:

https://networkofnature.org/species/

Or this:

Plant Database

Wild Strawberry (Fragaria vesca)), Self heal (Prunella vulgaris))

How do I fit this into my garden practices?

Some of these will arise on their own, like clover, lamb’s quarters, dandelions, etc. If they have not gone to seed, simply pull them like you would any weed and let them decompose on top of your garden soil. Alternatively, you can bring them to your compost bin to release their nutrients there. If they are a desired species, you can plant them right where you need them most. You can plan them into your vegetable crop rotations if they are annuals. The commonly used perennial comfrey re-grows quickly, so the foliage can be removed and used as mulch nearby. Planted under a fruit tree, you can let the process occur on its own each year as the foliage on top dies in winter and feeds the soil that way. This is a common permaculture practice that now finally has some research to back it up!

A permaculture-style vegetable garden

References

Tyler, Ben. (April 3, 2022). New Findings Further the Studies of Dynamic Accumulators. Cornell College of Agriculture and Life Sciences. https://smallfarms.cornell.edu/2022/04/new-findings-further-the-study-of-dynamic-accumulators/

Zarro, Greta. (July 20, 2020). Breaking Ground with Dynamic Accumulators. Cornell College of Agriculture and Life Sciences. https://smallfarms.cornell.edu/2020/07/breaking-ground-with-dynamic-accumulators/

Tyler, Ben & Zarro, Greta (Dec 2021). A dynamic accumulator database and field trials for six promising species. Northeast Sustainable Agriculture & Research Education.  https://projects.sare.org/wp-content/uploads/A-dynamic-accumulator-database-and-field-trials-for-six-promising-species.pdf

Some other interesting articles on Dynamic Accumulators:

Kitsteiner, John. (April 15, 2015). The Facts about Dynamic Accumulators. Permaculture Research Institute. https://www.permaculturenews.org/2015/04/10/the-facts-about-dynamic-accumulators/

James, Sean. (2011). Permaculture, the art of edible gardening. Landscape Ontario.com https://landscapeontario.com/permaculture-the-art-of-edible-gardening

Battersby, Sarah (2009). Love Your Dandelions, They’re Dynamic! Toronto Gardens Blog. https://www.torontogardens.com/2009/04/love-your-dandelions-theyre-dynamic.html/