Huge harvest of pawpaw/papaya-like
fruit in a cool climate.
As of Nov. 2013 my wife and I
had four adult Babaco
“trees” (Carica pentagona, a kind of cold-tolerant
pawpaw or papaya) growing inside an
unheated plastic greenhouse that leans against our sun-facing back wall. It is about 2.5 metres wide by 4 metres
long. Say ten square metres. The babacos’
leaves occupy most of the top of the greenhouse, but there is also a small
avocado, a fruiting Ficus coronata,
pepino bushes, a tamarillo, and passionfruit.
Inside the greenhouse the trees are growing in just 6
inches (15 cm) of rich soil, over an old concrete patio.
The babacos mature a few
fruits during the winter, when they are fairly stationary. Then as the Spring weather
warmed up from the start of September 2013 we had one or more fruits, weighing
about 0.7 kilos (that’s about a pound and a half for those still using the old
imperial units), maturing each week.
The babaco is a theoretically
perfect fruit, like strawberry, in that there is no skin or seeds to remove.
One eats the whole fruit.
I particularly like to eat one uncooked,
simply cut into quarters, dabbed with apple juice and stored in the
fridge. My wife Jan prefers them baked
for 30 minutes at 180 Celsius, with a little brown sugar. A Bhutanese friend chops them up with cheese.
This rate of fruit production
from the 4 plants accelerated in October until by late November 2013 we had
consumed or given away over a dozen large fruits, each around 700 gm. We also had
a table covered with a further 10 large
ripe fruits, plus 8 that had to be picked green when a branch broke. (These
were used as vegetables, e.g. in curries, rather than as fruit.) There were
a further 14 advanced fruits maturing on the “trees” to ripen over summer. Thereafter there was a hiatus in the fruiting
till some of the smaller fruits came on, and till three smaller trees become
adult. (With better management it should
be possible to have babacos fruiting
When I weighed these 18
fruits that we currently had in the house, they totalled over 10 kilos. Luckily
the fruits store for a month or more at room temperature, provided you pick
them before they are uniformly yellow.
Cultivation: How we grow babacos in a
chilly capital, Canberra, might seem an unlikely place to be reaping large
harvests of a close relative of the tropical papaya or pawpaw, Carica papaya. Yet we have found it surprisingly easy to do.
The flowers require no pollination, and the fruits,
which set automatically, contain no seeds. All parts of the fruit are edible.
Canberra, at 600 metres
altitude, in the foothills of the Snowy Mountains, gets about 100 frosts a year and
is not reliably frost-free until mid-November (the last month of Spring).
Frosts commonly return in May. The lowest recorded temperature is minus 10
Such a climate rules out
growing the true pawpaw/papaya outdoors. However its equally bountiful sub-tropical
relative the babaco, Carica pentagona,
is much more tolerant of persistently cool weather. The problem is that while
babacos tolerate sub-zero temperatures, perhaps even down to minus 6 Celsius,
they dislike frost on their leaves. (Hence
As best I understand it, the
problem with frost is that if a dry breeze moves over a frosted leaf at dawn
the frost can “sublime”, as chemists say. This means that it evaporates
directly from the solid to the gaseous state. In the process it may drop the
temperature of the leaf it encases to temperatures well below the ambient air
temperature. An alternative explanation, favoured by the Wikipedia article on Frost, is that "In the absence of a site nucleating the formation of ice crystals, leaves remain in a supercooled liquid state, safely reaching temperatures of −4 to −12 °C (25 to 10 °F). However, once frost forms, the leaf cells may be damaged by sharp ice crystals."
The obvious solution is to
grow babacos under the eaves of a house , and perhaps protected by a simple sheet of
plastic hanging down from the eaves. That way dew is less likely to get in, and
frost unlikely to form on the leaves.
I have found this worked well with strawberry guavas, but less well with
babacos. For babacos, it seemed, some kind of minimal greenhouse was
The door, here shown open, is simply a door-shaped
sheet of transparent vinyl held taut by the weight of a thin plank stapled to
its lower end. One rolls it up, with the plank, much like a blind. Black Velcro
patches help hold it in place when closed.
I also had to solve the
problem of drainage. Babacos need better drainage than our local clayey soil
provides. Growing them in very large
pots was one solution, and this also made it possible to lug the plants inside
and treat them as (rather attractive) ornamental pot-plants during the coldest
part of winter. However by the time they are 3 metres high, babacos need very
big pots. Also, potting-mix breaks down within two years. It compacts, and
ceases to drain reliably. So the replacement of potting-mix for such large plants became
Fate provided a single solution to both
problems. To explain it, let me describe our back garden. It slopes downhill
North-Eastward, into the rising sun. This is the perfect facing for a Southern-hemisphere
garden, since the slope also makes the morning sun’s rays hit the garden more
directly. The plants warm up quickly in the morning, and reach their ‘operating
temperature’ hours earlier than would happen on South-Westerly slope. At the same
time, the excessively strong afternoon sun is mitigated because the rays are by
then striking the garden somewhat obliquely. As a further blessing, the bulk of
the house (plus a slight hill behind it) blocks out the cold winds from the
South and West.
The warmest and most
sheltered part of the back garden was therefore right against the back wall of
the house, where the North-East-facing house-wall reflected the morning sun’s
heat back into the garden. (There is of course a similar warm spot in most home
gardens, against a sun-facing wall.)
And within this wall there
was a sheltered rectangular area, framed on one side by a bedroom that juts
outs, and on the other by a flight of brick steps going down from the back
door. This should have been the choicest
area for planting into—except that the previous owners had concreted it, turning
it into a patio.
The greenhouse in situ. The brick steps are just out
of view in the foreground, with a double safety-rail at the top of them.
I had long felt that this
concrete patio at our back door was a wasted area. Unable to plant into it, I
used the patio as a space to put a few favoured pot plants—until one day I had
I laid a single row
of bricks on their side about 2 metres out from the wall, then bought ten bags
of potting-mix (on special at the supermarket) and filled in the rectangular area
between the wall and the bricks with potting-mix. Obviously the depth of soil
over the cement was only a few centimeters—the height of a brick on its side.
Yet I planted out this area as if it was a garden bed. (I had read that
Parisian market-gardeners used to boast that they could grow perfect vegetables
upon cement. All they needed was a few centimeters of well-rotted horse-dung
over the concrete.)
The plant growth that
followed was magical, perhaps because the slight slope in the concrete patio underneath
guaranteed good drainage. (Patios are normally built with a slight slope so
that they drain). As well, the shallow soil guaranteed aeration. Also, although
the soil was on the acid side, plants could still get access to lime and more
alkaline conditions from the concrete below.
Despite the shallowness of
the soil, this patch did not seem to need much more watering than any other bed—though
it’s true that I do water it at least every 2 days in summer. (There is a hole cut in the side of
the roof’s spouting that drops water directly into it; so there is no need to
water it in weeks when there has been rain.)
Later I got this whole area covered
with a plastic roof, albeit with a fair bit of ventilation, and with
transparent plastic side-walls. It was a
very cheap lean-to greenhouse, with slits in the plastic roof so that rain-water fell through. The existing house walls provided two sides of
the rectangle, and bamboo poles, grown in our garden, held up the other two
sides and the roof. The transparent plastic was free. It had been wrapped
around a new lounge suite. (It worked beautifully for one summer. Then, since
it was not UV stabilised, it fell apart and had to be replaced.)
A new and much better
structure replaced it, with poly-piping rather than bamboo supports. My friend Bernard
Davis built it, and designed several innovative features that are shown in the
photos. These include a roof that can be partly rolled up in summer, since
Canberra gets the occasional day of 40 degrees Celsius, which would otherwise
cook the plants. The total cost, including labor, was about $900. The roof is standard translucent greenhouse plastic
(polyweave). This has the advantage of distributing the sun's rays more evenly
below. (In the photos it looks solid white, but most of the sunlight passes
through it.) However a greenhouse made entirely of this material would look
like a white barn, and the plants inside it would be invisible from outside—destroying
the magic of the enclosed space.
I found it surprisingly
difficult to buy transparent greenhouse plastic for the walls. Suppliers shook
their heads, or assured me there was no such thing. Eventually I bought what
Bunnings call “table-top vinyl” from their Flooring Section. This was available
in four thicknesses. The thinnest was not UV-stabilised, so I used the second
and third-thinnest varieties. So far, after nearly a year in place, the
material shows no sign of ageing,
tearing, or discolouring.
The vinyl of the outside wall
comes down to within about a centimetre of the ground. The gap provides
ventilation, which a greenhouse needs. (Some visitors worry that the
greenhouse encloses the bathroom window, and fear there will be “no fresh air”
for the window. I explain that a greenhouse is a windbreak but not an airlock. In fact the air inside it is always fresh.)
To foil the ubiquitous
Australian brushtail possum (a cat-sized leaf-eating marsupial, only distantly
related to the carnivorous American opossums) fruit-protection netting is stretched tautly a
centimetre or two above the roof. It does not lie flat on the roof. If it did, the
possums would soon learn to run over the netting without tangling their claws, and their sharp claws might cut holes in the roof.
Bernard Davis’s poly-piping and vinyl greenhouse uses
the existing house walls for support. Note the white bird-netting stretched
above the greenhouse roof (and over part of the house-eaves from which possums
might otherwise access the greenhouse roof). Note also the small soft-drink
bottle, whose orange top is visible. This is filled with water and suspended from the netting as a weight to hold it
taut. Not classy perhaps, but effective.
I have learnt it is possible,
in this minimal unheated greenhouse, to grow plants like babaco and pepino (Solanum muricatum) and passionfruit, which tolerate cold winters
but resent frost on their leaves. (The heat coming through the house wall has
so far been enough to keep off Canberra’s mild frosts. Minus 6 Celsius was the
coldest night last winter, 2013. )
In winter the greenhouse
begins to warm up from the very first rays of dawn, which penetrate directly
into it through the transparent side walls. By noon the heat-trapping
greenhouse effect is strong. Even in
midwinter, when maximum temperatures outside are often only about 10 degrees,
babacos continue to ripen and drop fruits (though the main formation and growth
of fruits needs to take place during the warmer months.) By the way, Canberra’s
inland climate is very sunny, with mean daily sunshine of 7.6 hours/day. It
probably gets more sunlight than the coastal warm-temperate city of Sydney to
its North, where frost is rare.
In summer the siting is not
so ideal. Partly because deciduous trees in the garden are then in leaf, it is
not till around 9 a.m. summertime (8 a.m. real time) that the sun’s rays hit
the translucent roof and begin to refract sunlight upon the plants below. By 10
a.m. summertime the first direct rays come through the transparent side walls,
and from 11 a.m. to 2 pm the greenhouse is hot (and needs to have at least its
window and its roll-up door open, if the outside temperature is approaching 30
Celsius). However by 3 pm the sun is starting to leave the greenhouse, and by 4
pm (summertime) the heat-stress has passed, with only the roof and a bit of the
Western side wall still getting direct sunlight.
Here the roof, of translucent polyweave, has been
partly rolled up to allow heat to escape during a heatwave in February 2014.
Three days of 40 degrees Celsius did not harm the babacos. The side wall of
transparent vinyl is almost invisible in the photo.
It seems that babacos love
these protected conditions. By contrast, when grown outside they don’t like hot
facings; and in my experience they fail to set fruit if grown in dry and windy places.
Inside the lean-to
greenhouse, our babacos’ trunks tend to slope outwards away from the house-wall
and towards the sun. This, plus the shallow
soil and the sheer weight of the fruits (with up to 8 kilos of fruit at a time
on each trunk) meant that they needed some support or restraint. So I simply tied
them back to an attachment-board on the wall, using old stockings.
Babacos, once they are a
metre high and growing strongly, form a new fruit with each new leaf. Hence
there is soon a staggering amount of fruit on a single trunk, with large
nearly-ripe fruits lower down and smaller and greener fruits higher up. Yet this process cannot go on forever. Although
Louis Glowinski in his fruit book refers to “the squat babaco” (by contrast
with the leaner pawpaw) the trees do eventually get 3-4 metres high. At this
height they tend, if grown in the open, to topple over in strong winds. (They are
of course best grown in a sheltered valley.) So the usual practice is to cut down each
trunk after it has borne perhaps 20 fruits (sacrificing the many small
unfinished fruits at the top) and allow a single lower shoot to replace the
lost trunk. (Babacos make side-shoots more readily than pawpaw/papayas do, so
there are always shoots in waiting.) The
plant is then out of production for several months until the new trunk is large
enough to begin forming fruits.
How high can a Babaco go?
Meanwhile the removed top of
the trunk is divided into metre or half-metre lengths that are used as giant
cuttings. My practice is to remove all
the fruits and the larger leaves from such a cutting, enclose the remaining smaller leaves near
the tip in a plastic bag with a few drops of water, and lay the plant on its
side in the shade. However I leave the base of the trunk outside the bag and
exposed to dry air for at least three or four days till it has begun to callus over.
Then I plant it in a large pot (with ordinary potting mix, and use a few empty smaller
plastic pots, jammed in beside the trunk, to hold it upright until the roots grow).
The cutting stays in a greenhouse or other shaded place, and with the plastic
bag over the top for a month or so. Then the bag is removed; and the plant is
hardened off for a further month, before it can be moved outside. Of course in a very humid climate fewer
precautions need be taken against the cuttings drying out.
My original babaco plant has
now multiplied into over a dozen, of which about 5 small and 3 large ones are
growing in the greenhouse. (I also have
a few for sale.) While in theory babacos
might be allowed to grow to their maximum height inside a sheltered greenhouse,
our greenhouse is not quite tall enough to make this possible. So once their
leaves start pushing up against the roof, it is time for me to remove the main
trunk, and let a side shoot start to replace it. The aim is to have about half of the plants
at any one time in maximum production phase. This means that they currently have
a well grown trunk, with ripe and ripening fruits on it. The trunk should have
emerged into good light and not yet be too near the roof.
I hope others will try this
system for cultivating babaco.
Finally, you may be wanting
“What are babaco fruits like? Are they similar to papaw/papaya fruits?”
They are similar in size, but
their ridged-torpedo shape is distinctive, and their taste is quite different.
As fruits, Babacos are superior to pawpaw/papaya in
the following ways:
There is no
seed-mass to throw away. In fact no seeds at all. Babacos are a seedless hybrid
between two Carica species. They set fruit automatically without
pollination. (Since there are no seeds, humans have perpetuated this chance
mutation, which may have occurred just once, for many hundreds of years by striking
There is no rind
to dispose of. The entire fruit is edible, including the skin. It is thus a
theoretically perfect fruit like the strawberry, or the Large Oval feijoa.
It has a kind of
effervescent taste—hence the marketing name “champagne fruit”.
pawpaw/papaya, babacos have a strong and (to me) delicious scent that is an
important part of the taste. When mixed into a fruit salad they are one of the
most pungent and enriching ingredients.
They are also an
interesting replacement for figs in fichi
The fruit goes on
ripening after picking, but quite slowly.
It is remarkably
tough. If one part is bruised when it falls off the tree, the bruise tends not
to spread. Babaco fruits can be transported with less protection than pawpaw.
Fruits are edible
even when green. The green fruits are sub-acid, and so may be used, cooked, in
any recipe where you would use tomato or pimiento.
pawpaws, contain the meat-tenderizer papain.
This makes them particularly good as a vegetable to use in curries or
with meaty stews. Hence when the trees are producing heavily, babacos can be
used both as a fruit and (while still green) as a cooked vegetable.
Babacos are inferior to papayas/papaws in the
They are not
nearly so sweet. This may be a serious problem for people in Western countries
who expect even tomato sauce to be full of sugar.
everyone likes pawpaw/papaya on first tasting it, some people don’t like
babaco, or only care for it with lashings of sugar. (One solution is to combine
it with ice-cream, for which it has an affinity.)
Many people don’t
know any recipes for cooking it. Also some, being unfamiliar with babaco, remove
the thick edible skin—and then complain that the soft inside part lacks
Though there are
all kinds of tropical flavours in babaco, the dominant taste is a bit like an
effervescent lemon-scented watermelon, which some people find un-exciting.
Unlike pawpaw, it
is not much improved by adding lime or lemon, since it is already sub-acid. Apple-juice
or apple-concentrate is a better idea.
somewhat watery, especially when over-ripe. Some people, unfamiliar with the
fruit, over-ripen it to the point where it has little texture and too much
To counter this,
fruit should picked before it is uniformly yellow. If left on the tree till
yellow it also tends to drop, and bruise.
Once over-soft it
is not suitable for cooking, though it may still make a great smoothy. (When
green it is quite firm and chewy, even after being cooked in a stew or curry.)