Ice cream bean, Inga mortoniana
Scientific Name: Inga mortoniana
Family: Fabaceae
Extract from Quandong Vol 19, No.4. Fourth quarter 1993
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.
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