Stacking Functions Part 1 – Pawpaw Perfection
“Stacking Functions” – we hear the phrase all of the time in the Permaculture world, but what does it really mean? Is it simply another variation of “two birds with one stone”? It can be used that way, but at it’s best, stacking functions really is a system-wide philosophy. We look at overall needs on our site and match inputs and outputs in mutually beneficial ways. Over the next few months, I’m going to take you all on a tour of some different designs with awesome and creative function stacking, starting with a design I’m really proud of on my own site. It began with observations about 3 different elements in our system. But first, a little background on PawPaws.
The Pawpaw is the largest native North American fruit, with loads of benefits to enjoy. In late summer it produces clusters of a delicious, creamy fruit, it’s shade tolerant, browse resistant, a butterfly host plant and can handle wet feet. It’s a great tree to plug into those dark corners of the property that you’re looking at and thinking.. what can I put there?? It is flowering now (mid-April), and the flowers are small and dark red, hanging upside down from nearly naked branches as the leaves begin to emerge. A small, resilient tree that produces heavy yields, it's perfect for the homestead. Now that we know the basics, on to our observations.
1). We have a challenge on our site, and it’s of our own making. We process thousands of poultry animals here every year – chickens, turkeys, and ducks. The water coming out of our outdoor poultry processing facility is full of Nitrogen and nutrients and flows downhill toward a pond on our property that overflows into a crick that feeds into Raccoon Creek, then the Rivanna, then the James, and on out into the Chesapeake Bay. We don’t want to send all of this extra nutrient into that system so we need a creative solution.
2). One of our small business enterprises is oyster mushroom production. We’ve frequently got a lot of “spent” mushroom substrate (most often a sawdust and/or grain base/mixture) that is no longer useful in commercial mushroom production, but still has a lot of life left in it to grow and spread. During our last PDC course, Eli Talbert of Talbert mushrooms was giving a guest lecture and said something that caught my interest. “Mushrooms are just Nitrogen gobblers. Especially oysters, they’ll eat almost anything”. I knew this in principle, but a new lightbulb came on in my head.
3). We have a love of Pawpaws, and are starting to work towards propagating them. We purchased 20 bare root trees this winter to start a pawpaw patch that we can later graft desirable varieties onto. This way we’ll grow the top notch varieties and produce our own scion wood (mini function stacking) so that we can propagate specific cultivars.
With these observations we were able to creatively meet a need, reduce our waste, and increase our abundance. Here’s how: We dug a series of swales going down our hillside next to the processing plant and are in the process of filling them with wood chips to act as a sponge and filter. There are 4 of them so far, and we intend to add more this summer and extend the system further downhill. The top swale catches the runoff from processing at its Easternmost end, and it’s dug at a very gentle grade so the water moves downhill to the spillover point at the Westernmost end. The spillover carries the water to the next swale where it enters on the West end and flows gently downhill to the East, where there’s another spillover, and so on. In this way, the water zig zags slowly downhill through these swales and has a lot of time and space to be absorbed and filtered before entering our watershed.
But here’s where it gets cool. Pawpaw flowers have this really cool strategy for reproduction. They have the dark red, veined appearance of raw meat. And they stink! They smell of decay, some even say they smell like rotting flesh. These two characteristics attract carrion flies, which are the pawpaw trees’ pollinators. And guess what enterprise on our farm attracts carrion flies? Poultry processing! Our composting poultry “leftovers” (any guts we can’t use, feathers, skin from peeling the feet, blood etc.) always attract flies, and we’ve located those piles at the top of the swaled. Aaaand, Pawpaws can handle wet feet. They won’t mind being planted in a place that gets periodic heavy wettings (processing days use a lot of water). Pawpaws also have a deep taproot which will help stabilize the berms on which they’re planted.
And here’s where it gets cooler. Whenever we have leftover mushroom substrate, we just throw it on top of the wood chips in the swales and let the mycelium “run”. Those oysters can gobble up all of that rich Nitrogen from our processing days and keep it out of the waterways. We won’t eat those mushrooms, we’ll leave them to keep reproducing. They’ll also help facilitate a fungal network in the soil, which was recently turned over from grass pasture. This will help the survival of the trees which have evolved in forested ecosystems with a healthy fungal community.
So our main inputs here are labor and design. It took a lot of work to dig swales (thanks interns and Spring 2019 U of R PDC Students!) and plant the trees, but the harder bit was establishing the design concept. Once established, the outputs are huge! Clean water, nutrient absorption, delicious fruit, fungal communities, making use of the flies on site, swale stabilization, shade, aesthetics, scion production, seed production, pollinator hosting (Pawpaws are a butterfly host tree, in fact zebra tail swallowtail butterfly larvae will only feed on Pawpaws and nothing else) and more.
This is just one example of what stacking functions can do when applied on a whole system level in your Permaculture designs. Stay tuned this summer, we’ll take a look at a lot more interesting and inspiring design examples. Enjoy, and go plant a Pawpaw!
Daniel Firth Griffith