Tools and Techniques- Inga Alley Establishment

Recently I completed what on the surface would appear to be a very simple job: sticking a few seeds in a hole in the dirt. I harvested fresh seed from a mature ice cream bean tree (Inga edulis) in our local park in order to plant a second Inga alley cropping area on my fertile creek flats. The pods on the low hanging branches were picked into a bucket, taken home, and then split open. I have found they can be harvested a while before the pulp inside sweetens and swells up, meaning I can beat the local bats to the pods. The seeds are surrounded by a white pulp that can be gently removed by splitting the membrane with a fingernail. But the easier way is to soak the pulpy seeds in a few changes of water, causing them to swell up and split so they can just pop out on their own. About 25 % of the seed didn’t pop out but I had plenty that did. I am pretty sure those still in their membranes germinate well enough, but the sweet flesh might attract rats.

The seed was left in a bucket but not soaked in water to prevent rot and covered to prevent them drying out. Unlike most seed the Inga seed are born like naked green embryos that cannot survive desiccation. The weather was very rainy at the time and I was recovering from a cold, so I put off sowing as long as I could. When I saw the seeds had started germinating I knew it was time to get them planted and just put up with coming home soggy. The part germinated seed would still establish but were now a little more delicate to handle, and needed to be oriented with root shoots facing down, slowing planting just a little. The area in question is about half an acre on our creek flats where the soil is deep and silty due to a history of flooding. It was originally kikuyu grass which had rows of pigeon pea planted oriented north to south to allow more winter sun down the rows. The kikuyu died off during our pasture die back and was replaced mostly with cobblers pegs (Bidens alba). I planted a few rows of Tithonia diversifolia to one side that I now regret since they are more of a pain to manage than Inga and will remove eventually. I also trialled some winged yams, lima beans and turmeric at various times that have done fairly well with no attention. After planting out crops in the first established Inga alley area that formed a canopy after about five years I decided it was time to plant a second such area, with a third one planned to go in next year on the last suitable piece of creek flats.

Getting to this point has required a series of increasing investments of time and energy in order to manage risk successfully. If I had tried to fast forward to this point I would inevitably make big mistakes and waste a lot of time and energy. Someone reading this might be tempted to rush out and also plant a large area with Inga but this account is meant to be a much more useful meditation on how to invest resources gradually and wisely rather than a recipe to follow. What worked for me may well fail utterly for you for a wide range of reasons that are invisible until they are unavoidable.

The first step was observing local Inga trees in order to secure a source of seed (and to be confident they grew in my conditions). Since the seed cannot be stored they are almost never offered for sale. I initially harvested a couple of buckets of seed and only accidentally discovered the water soaking trick when I left a batch that I was slicing open by hand to go do something else. These seed were initially sowed in small tube pots, with 2-3 seeds in each pot since I wasn’t confident about germination rates. I also sowed some in group pots then did the fiddly job of separating seedlings to pot up individually and grow on before transplantation. I now know that one large seed per pot is plenty since they almost all grow. I also know that rats sometimes dig through my pots, so the best tactic is to keep freshly sowed tube pots up high away from the green house for a couple of weeks until germination is mostly complete. After this I also had some seed left over so experimented by sowing them directly into grassy hill pasture in a corner of the farm the cows were excluded from during wet weather. When you are unsure about the best approach your most limiting resource is knowledge. In such situations it is always a good idea to try multiple approaches. My other limiting resources were seed (only available once per year, but fairly large quantities at that time provided I harvested on time), pots (only so many tube pots and space for them), and time/labour (both in the short window for direct sowing, and later on for transplanting out potted seedlings). It is worth keeping track of what your limiting resources are and basing your decisions around them. If I had put all the seed into the same conditions the chance of them all failing and all the time and energy being wasted would increase dramatically.

Those original potted seedlings were grown out until the following spring then transplanted into what is now my first Inga alley plot. The thick kikuyu grass was sprayed out before transplantation, more to make planting easier than to help the trees compete. Luckily that spring wasn’t terribly dry so about 70-80 % of them survived. The seed sowed directly into the grassy pasture apparently disappeared without a trace, so I assumed it was a failure. A couple of years later the trees emerged from the pasture, and now make a vital fodder bank for the goats during droughts. They also showed the Inga can take direct sowing even in highly competitive conditions. I tried sowing the gaps in the Inga alley direct in following years and had about 70-80 % success rate, the same as the much longer and more resource demanding route of growing and transplanting seedlings. For my second Inga alley I decided to establish it by sowing direct to fill all of the positions, then keeping some seed back to fill gaps with tube grown seedlings in spring, and to resow gaps direct the following year, in order to reduce total resources spent.

For my first Inga alley I had no direct experience on how to arrange the rows, so I relied on the work of the to guide my spacing. But I wasn’t convinced that their optimum would be the same as mine. So I put in four rows of trees, with the spacing between them set to the recommended distance for the one row, then one a little wider and another a little narrower. Then I planted a final Inga row about twice the recommended spacing away. I figured if the closer recommended spacing ended up being perfect I could plant another row in the wide gap later on. Now I have finally had a chance to plant crops in the system I can make my own mind up. The recommended spacing I find is a bit too close for my purposes, with the variations either side not making much difference. The slightly expanded closer spacing seems to be good for shade tolerant crops like turmeric, ginger, cocoyam and taro. The recommended close spacing allows the Inga to regrow and shade the crop quite rapidly, which is fine for sun loving crops if you have plenty of free labour to keep trimming the Inga. Labour is probably my limiting factor in these spaces since it is just me working them. The double wide spacing proved to be much more useful for sun loving crops, though required a little more time to weed the cobblers pegs before planting a crop. The Inga still produced a useful amount of mulch when cut back to help manage those sunnier spaces.

Based on all this I decided to do a mixed spacing system in the new second Inga alley area. The area was about 40 paces across, leaving room for three double rows of Inga at the recommended spacing of about 5 paces (producing three cropping lanes for shade tolerant crops). Between these double planted close spaced Inga rows are two long double wide rows of 11 paces for sun loving crops, but with convenient access to the Inga mulch to assist management. My paces are about 60-70 cm for reference. I always count out spacing a few times since pace length varies in deep weeds. Laying out these sized areas by hand can be a bit tricky but I have gradually accumulated some techniques to get a well ordered lay out. Straight lines are not the tool of the devil, and make management on a larger scale much easier. I marked out the corners of the space, with a slight incline to the north showing where the silty flood plain stops. To the south a power transmission line marked the boundary, since tall trees aren’t permitted under them. I might use this space for more intensive cropping later. I used mature trees visible near the power lines on either side of the space to mark where I could plant to. To mark out positions I used electric fence pigtail posts, with a convenient foot that can be pressed into the ground. The white tops are easily visible over the cobbler’s pegs. I paced out the ends and marked where the rows should go, then strung up white plastic electric tape to mark out the space. At several places along the length of the rows I remeasured the 5 paces between the electric tape lines, plus did visual checks that the lines were straight enough. I then took my hoe along the marked rows and made a shallow hole every 2 paces. Once they were all in place I put my hoe down and went along with my bucket of seed, using my boot to push the soil back over them as I went. Doing one job at a time is much more efficient than repeatedly picking up and putting down the hoe and seed bucket (though taken to extremes doing one motion all day can have a negative impact on the body). They like to be about 1-2 cm deep to balance rat protection versus ease of emergence. I have found rats and mice are much less likely to dig up seed during wet weather. I wonder if they simply can’t smell them as easily underground or don’t like getting their paws muddy. The whole planting job took about six hours, split over two mornings.

Along the way I noticed a rather large carpet python trying to sun itself under the cobbler’s pegs in the middle of a double row. It didn’t even twitch as I continued to work beside it. I also saw a large eastern brown snake on the way home through the weeds, but didn’t stop to take a photo. I also found a nest full of eggs for a plumed whistling duck on the bank of one of our dams. One of the rows featured a very healthy nest of our local paper wasps that gave me a few stings for blundering into them. I squashed up some young cobbler’s pegs shoots to put on the sting to calm it down, but I am pretty much immune to them now after so many encounters. I skipped planting seeds under them since I can always fill in the gap later.

To most people the space in question looks like a terrifying jumble of noxious weeds that need to be beaten and sprayed into submission. Initially I was a bit wary of wading into the weeds but now it is like second nature, like how people adjust their gate to walking on sand. Humans are supposedly plains loving species that like to see where they are going, though there are forest and jungle people as well who are more at home in a thicket. I’m not especially worried about the snakes, especially near the dams I usually only see red belly black snakes that are very docile, not especially venomous and eat the more dangerous brown snakes. I think the brown I saw recently is the only one I have ever spotted beside the dam. With plenty of escape routes the snakes are usually out of my way before I even see them (though I move a bit more slowly on cold sunny mornings when they might be surprised before they warm up). While the risk from the snakes is not zero, it has to be balanced against all the good they do. Our side of town has no resident brush turkeys since the pythons keep them in check. We seem to have a large enough chunk of territory without any roads running through it so the python population is very healthy since you rarely see them dead on the road. The brown snakes also help balance out the inevitable rat populations that occur whenever grains are grown. My theory that piling up Inga branches would create a habitat for them seems to have worked since I have spotted a couple of large ones lurking around the piles, and rat damage to new corn seedlings was reduced a lot this year.

The cobblers pegs are often a source of great frustration for people as well, with their seeds sticking all over their clothes. On reflection I think they are a net positive as well. When the pasture die back killed our grasses the cobblers pegs quickly moved in to stabilise the soil. They build better soil organic matter than grass in my experience. We have clouds of wild bees pollinating them. They are easier to hoe out of the way than grass to plant into, and the resulting plants grow through them better than grass, and better compared to those on bare ground as well. As for the seeds on clothing, the time I spend cleaning my clothes after working in the weedy paddocks is a tiny fraction of the time I would spend mowing, spraying and whipper snippering to maintain cleared paths all over the farm (that I would mostly only use once in a blue moon). The amount of seed is highly seasonal, with seed ripening now to reach their peak in late autumn. I try to time my work to seasons with less seed present, but during bad times I walk paths with a bamboo pole to knock them off before starting work (much quicker than firing up a whipper snipper). Their self spreading nature also saves me from having to collect and distribute them, a job I wasted lots of time on trying to establish other pasture plants. The seeds prickle a little but rarely hurt, unlike a whole host of other weeds like Scotch thistle that would probably move in if I could wave a magic wand and make the cobblers peg disappear. And in the space in question the Inga will grow up and over the cobblers peg in a few years, during which time I will need to do nothing but wait for the Inga canopy to close in a few years time. After a morning working in the fields I now sit out under a mulberry tree, stripped down to my underwear, while I pick my clothes clean and watch the dogs run about. It doesn’t feel like wasted time. Sometimes if I listen carefully I can hear a whipper snipper growling in the distance and wonder if I will live long enough to hear them fall silent.

Inga pods being processed. A well aligned bend snaps the pod, allowing it to be stripped open.
Soaked pods starting to split open. Change the water every few hours to prevent spoilage.
A shallow hoe hole with a couple of presprouted Inga seeds. If you have seed spare putting a few in each holes reduces the number of spots that end up with none.
Turmeric and winged yam doing their own thing in the weed patch, a good sign that they will respond well to a little more management later.
A lazy python tolerates me fussing nearby. I couldn’t see where the head was hidden, but realised that was a plus.
A whistling duck nest hidden in the weeds. Just makes you want to get the mower out and tidy up the universe right?
Cobbler’s peg removal time. Selecting clothes that doesn’t attract them too badly helps.
A double Inga row marked out with white electric tape and pigtail posts. Come on in, the cobbler’s pegs are fine.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: