Normal practice is to plant the trees in poly bags.
These are filled with forest soil that also contain the necessary microorganisms (nitrogen fixing bacteria and mycorrhizal fungi that take up the phosphorus). For more details on ensuring these microorganisms are present see Seed Collection and Planting out on this page.
Bags containing seedlings should be kept moist prior to planting and be planted out within a few days. Seedlings are generally more robust than planting out seeds, though both can be used.
The disadvantage is that the bags cost money and create waste. For that reason we have been experimenting with planting directly into the ground.
Planting directly in the ground (bareroot method) has been found to be successful in some of the planting done in our Ecuador project, and the local project manager claims that these trees grew better than those first grown in bags and then planted out.
We have done some experimentation with planting bareroot in a nursery but do not at present have results to report.
Inga has also been successfully propagated by cuttings. This has the disadvantage that there will then be no genetic variability.
Comments from one of our Cameroon partners, Atanga Wilson:
You have now planted Inga seeds in three ways: polybags, bareroot and direct into the ground. Which method do you think is the best?
Polybags or bareroots.
The choice depends on how far the nursery is to the farm where the Inga is to be planted. It also depends on the regularity of rain fall. But Inga seedlings raised with biodegradable poly bags are usually the best option.
You say some of the bareroot seedlings died after they were transplanted. Why do you think they died?
This happened when they were transported by walking long distances on foot from the nursery to the farm in the hot sun in the middle of the day.
How did the compare with the ones you first grew and planted in poly bags?
The poly bag ones do better if they are planted and there is no rainfall for 3 days after transplanting. But there is no difference from those with the poly bags planted in the morning and evening in the hours when the rain falls.
How does planting the seeds directly into the ground compare with these other methods?
Seeds planted directly grow very slowly because they don’t get the same care on the farm as they would have in the nursery. They face more of a shock when there is a dry spell or absence of rain for a week or two.
In summary, I recommend biodegradable poly bags for Inga nurseries. If no biodegradable poly bags are available then go for bareroots Inga nurseries and trek for very short distances to plant the bareroot seedlings.