ICE CREAM BEAN - INGA MORTONIANA

SCIENTIFIC NAME: Inga species
FAMILY: FAMILY: Fabaceae

The genus Inga is commonly referred to as Ice Cream Bean due to the characteristic white, fluffy melt-in-your-mouth pulp surrounding each seed. Palatability varies from species to species. In the humid sub-tropics of northern New South Wales, Inga mortoniana, of all the species tried, is both the best adapted and tastiest. The original material grown on the NSW North Coast was collected in a highland market-place of Central America.

Other species of Inga on trial here (I. spectabilis, I. edulis, I. exilis, I. paterno) have all grown strongly, and all make strikingly handsome specimen trees, but none have fruited well. Contrary to published data (In Lost Crops of the Incas, BOSTIO, Washington, 1989), which states that isolated Inga trees do not bear fruit because they are self-incompatible, all the non-bearing species I have planted here have partners within pollinating distance, and the original Inga mortoniana tree was on its own when bearing huge crops. Bearing commenced at three years, with hundreds of 7-20cm golden yellow pods by five years.

Nitrogen Fixing
The most outstanding feature of Inga mortoniana is the massive production of nitrogen-fixing nodules. I have never witnessed such massive numbers of nodules on any other legume. Last year, digging four metres away from the nearest Inga, I found that the roots were heavily laced with nodules like strung beads on all available root surfaces. This feature, combined with ease of growing in the nursery and establishment in the field, make this species extremely useful for soil rejuvenation.

With that aim in mind, I planted over 400 trees in a paddock which I have interplanted with a range of other species. This, their fourth year, found me for the first time going at them with the chain-saw, lopping them and letting them lie as trash, as I try to recreate the forest floor in as short a time as my low-maintenance program will allow.

Intriguingly, seeds are polyembryonic - weird and unexpected in a pioneer species where the opposite would be expected, to whit, great variation in the gene pool to maximize adaption to various sites. With the excellent coppicing ability, these trees can be continually cut back. If at any time trees need to be removed, chainsawing at ground level and repeated slashing will kill them: the underground parts rot, helping restore soil health.

Trees are readily propagated by directly sowing seed into 150 mm pots, and they are ready for field planting in a year. All my trees have been established from 150 mm pots. The species is very resistant to Roundup herbicide, much more so than clover.

Pests
Inga mortoniana is the only species to ever have mites in the field here, but this was only on a couple of trees; it went untreated and disappeared. The biggest problem is a seed borer that can damage up to 90% of pods, rendering them unsuitable for sale.

Adaptability and Value
This species has proved adaptable to all sites, from constantly moist to dry, heavy soils to light, and is hardy to at least -3°C. I planted 60 trees only 400 mm apart on good quality basalt soil, and after three years they were an effective windbreak 4 metres high and fruiting!

The new growth is an attractive reddish-bronze and the white flowers pretty. All Inga species have amazingly-shaped pinnate leaves. Traditionally, some Inga species (I. vera) have been used as shade and support trees in plantations (coffee, vanilla, pepper). Most Ingas have valuable timber properties; judging by the density of Inga mortoniana wood at an early age, this is a particularly valuable species. The only limitation is a strong tendency to branch. Ingas are also good fodder and street trees.

This species is naturalising here, and over time could prove competitive with Australian pioneers such as Acacia melanoxylon. Even with that possibility, this is an outstanding multi-purpose tree. It should be noted that the identification of this as Inga mortoniana is only tentative, positive taxonomic identification has yet to be made.

Paul Recher, Fruit Spirit Botanical Garden, Dorroughby, NSW
Extract from Quandong Vol 19, No.4. Fourth quarter 1993

DATE: January 1995

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