The term bioaccumulators refers to the usage of perennial and annual plants that are known for their capacity to “mine” minerals and/or “secrete” substances that are very important for the garden ecosystem.
While in Nature there are many, many plants that can perform the functions I will mention, I have chosen a few that are viable in my climate zone, and for the most part, I’ve selected among those that I’ve worked with, one way or another.
What are bioaccumulators
Comparing plants to each other in terms of how well they perform a particular function is a very hard thing to do, for the simple thing that Nature works through competition and collaboration. Through successive mutations and natural selection, today we have a multitude of plant solutions to various issues.
One way of setting them apart is by availability related to seasons. For example, Borage and Comfrey, being from the same family, perform similar functions, somewhat resemble each other and for the most part cover the same climate types.
But even in my zone 7b summers, comfrey (which I largely favor, personally) will greatly suffer for around 4-6 weeks, because of the heat; on the other hand, borage will be more “stoic”. It grows somewhat less than Comfrey, but its leaves are still “available” for mulching; if we’re confronted with drought, the disparity is even more evident. Comfrey will die back to its roots, and will come when the humidity of the soil allows for it.
But for 80% of the growing season, I’ll go with my personal “champion” (why Comfrey is my favorite Permaculture plant: https://vinepermaculture.com/why-is-comfrey-so-popular-in-design/).
Therefore I’d like to present you with my own “definition” of bioaccumulators – it’s a selective list which I hold dear, for it allows me to overcome obstacles (need for organic matter, mineral deficiencies), perform diverse functions (insect habitat and food), and even create beautiful landscapes.
The only real criteria to distinguish between these plants are those imposed by the project; if any of them is already featured on site, through natural processes or not, that is a clue as to where I should start from. Which brings me to a second question:
Why and where to include them
Before starting a list of bioaccumulators, as a Permaculture practitioner you should analyze the project and also your personal situation. For example, time availability on a weekly basis, or at a particular time of year, can tilt the balance in favor of one element or another.
In a hypothetical scenario, if you’re available only for a limited time to garden, but you’re able to have a winter cover crop, then White Mustard can be a very good performer, as it will grow incredible biomass (as well as accumulating vital nutrients, starting with Nitrogen) which is ready to use in spring.
So while time availability during the growing season might seem like a limitation, it doesn’t have to be; working with Nature, we have my options. If we’re sticking to the same initial criteria, then Dandelion, another item on my list below, will also perform greatly as it will be one of the earliest plants to flower and produce biomass in spring.
There are no “perfect” choices when it comes to selecting bioaccumulators, it’s more a question of attending to the needs of the garden. And I’ve chosen this particular topic – time availability – to serve as a reminder that Permaculture is also about humans. Care for the people is actually included in Care for the Earth, and we need to hold in our awareness that we’re an integral part of the Ecosystem that we’re designing.
Reading the soil life
Weeds as bioindicators – this is another “hot” topic for human beings. Unfortunately, we can become so attached to an outcome which we think appropriate for gardens, that we ignore that not all soils are created equal.
Just as everyone of us deserves to be loved and cared for who he or she is, and does, soils too should be appreciated for who they are, and what life they already support; if that happens to include the hard-working plants that we call “weeds”, we should spend some time observing before taking any action.
As much research done in recent years has, plants that have self seeded in certain patches of soil have done so for solid reasons: their germination conditions have been met.
Going with an element I’ve already mentioned, Dandelion will mostly appear where there is compacted ground. On top of bringing back to the surface important elements (and this can be for human nutrition purposes), it also performs the task of breaking up the soil and making it more hospitable for other plants.
Vital to intensive gardens
Keeping in mind that a garden is a very intensive project, both in energy expenditure, but also in knowledge, we have to realize that the higher our goals are, the more inputs are needed.
While it has become trendy, even for Permaculture projects, to feature “popular” inputs such as straw, leaves, grass clippings, animal manures etc. the reality is that these also come at a cost. Sometimes, it’s what we have to start with, and we need to be grateful for it; but using bioaccumulators is a must in sustainable gardening.
Becoming a gardener is synonymous, in my humble opinion, with learning to work with these wonderful plants that are featured below.
A few examples
This blog entry is unfortunately too short to do justice to any of these plants’ importance, so I’ll simply list a few below, and promise to bring the spotlight to each, in future articles:
- Yarrow
- Nettles
- Borage
- Comfrey
- White Mustard
- Cardoon
- Marigold
- Dandelion
- Plantain
- Elderberry
My hope is this article will enable you to see the added value these plants bring. Most are actually edible, at the very least for animals, so those nutrients can be made available both to them, and to the plants (soon after), through animal manures.
The cycles of using bioaccumulators are virtuous; once started, the increased life, in quantity and diversity, will lead to more yields, and balance can be reached sooner rather than later.
