We are planning to trial three or four native species of Inga, the most common of which is the domesticated Inga edulis. Because we want to develop the approach in a way that can be easily be replicated by our partner communities we source seed locally. Inga seeds are known as recalcitrant seeds, that is they have no dormant stage as most seeds do and so cannot be stored for any length of time. So the seeds strategy is to hit the ground running and it is not uncommon for the seeds to germinate in the pod. It also means that we need to sow the seeds within 48 hours of harvesting them. We start by collecting fruits, shelling the pods and removing the sugary white aril.
Because we are using Inga, in part to harness it’s soil-fertilizing Rhizobium bacteria, we need to make sure that the germinating roots encounter them. To do so we collect nodule-bearing roots from local Inga trees and grind them up in a mixture of water with some soil in a large basin. Then we place the freshly shelled seeds to soak in this overnight. The idea is that the bacteria escape the ruptured nodules and infect the seeds.
The seeds themselves vary a lot in size, shape and colour. They are shaped to sit vertically in the soil and the base of the seed has four anchoring projections that keep it upright and protect the emerging roots. The seeds need to be sown vertically, the base down and with the top of the seed sticking out by a few mm from the surface. Once sown we sprinkle a layer of soil over them and water them well. Because the seeds have no dormant stage germination is instant and after just two weeks the seedlings are 10-15 cm tall.