Plant Profile- Mango

Despite its reputation as the king of fruits the mango represents a great example of a plant that is right on the edge of being a marginal crop for me, though the increasingly monsoonal conditions due to climate change are shifting things in its favour. In my zone the majority of mango varieties drop their fruit when their flowers are infected with a common fungus called anthracnose. The majority of the crop is lost whenever the rain or humidity levels are high enough at a critical time during their spring flowering. Some varieties have moderate levels of resistance and offer a glimmer of hope. In addition to this when we do get a sufficiently dry spring then every large tree in the district gets weighed down with so much fruit that people cannot give it away. Such seasons happen every 3 to 5 years and usually coincide with a late spring and early summer drought. Luckily mango trees are very drought tolerant and usually produce good quality fruit even without much rain. Lower humidity also seems to reduce fruit fly pressure in these years, though they only rarely hit mangoes and usually after other damage has already occurred. Because of all this I don’t see the point in growing any of the anthracnose susceptible varieties since I can already pick all the fruit I can eat during those years with zero investment beyond time spent harvesting.

The anthracnose resistant varieties don’t produce three to five times as much fruit as the susceptible types that only fruit sporadically. Fruit and nut trees need to build up internal reserves of resources to allow them to carry their crop to maturity. The susceptible varieties accumulate higher reserves during wet years when their fruit abort, leading to massive crops during dry years. The resistant varieties produce about the same amount of fruit in the long run, just more evenly dispersed between the years. My favourite resistant variety is Nam Doc Mai, a variety from Thailand, with small pointed fruit on a medium sized tree. This variety has the useful property of producing polyembryonic fruit, meaning that each seed produces multiple seedlings that can be teased apart after germination, and that those seedlings are most likely to be clones of the original parent tree, or very close to it. Dry the seed off after removing the pulp then cut the thinner end open with secateurs. If you cut the embryo here it will still grow. Tear the seed coat off and check for weevil larvae. Embryos with a little damage usually still germinate if the weevil larvae are removed, and you can save wasting space planting the badly damaged ones. This means that I have been able to buy delicious Nam Doc Mai mangoes whenever I see them for sale and grown my own trees, saving a huge amount of money. Through trial and error I have found that mango seedlings transplant at higher success rates if grown to a bigger size than other species, usually at least 30 cm tall in a larger 20 cm diameter pot. They transplant best in January/February when the established trees are flushing with new growth after fruiting. I am also planting a few types of banana mangoes, and a few unnamed heritage types I have sourced from old farms. I plant my seedlings fairly close together, so that as they mature approximately half of them will need to be thinned out, meaning I will be left with trees that are above average.

I had one small mango tree, probably a common Kensington Pride/Bowen, on my farm when I moved in. This was the first year it produced a useful amount of fruit, so once the bats had knocked a couple down I got out the picking pole (a pool skimmer handle with a wire loop that has some panty hose sewn onto the edge to stop fruit dropping and bruising) and cleaned off the tree. Many tropical fruit can be picked just before ripeness to beat the bats and birds then ripened in relative safety indoors. This one small tree gave me about 40 kg of fruit, which when processed gave about 15 kg of flesh. This was frozen in zip lock bags for use in smoothies and should last about 4-6 months. About 10 % of the fruit were discarded due to rot or damage, tossed to the geese who fought over them. This tree is in the old cattle holding yard and the goats have started to slowly ring bark it. Given its poor previous performance I didn’t bother trying to protect it. It is quite likely the partial ring barking has cinctured the tree and increased the fruit yield by preventing sugary sap from returning to the root system.

It is worth roughly analysing the output of this little tree from both a financial and energy perspective. That 15 kg of mango flesh is worth about $105 if I allow it to be equivalent to frozen imported cubes. Fresh Australian mangoes retail about $6 per kilo, about $12 per kilo for the processed flesh, so at most $180 worth of product. The electricity for the chest freezer plus wear and tear on the machine is worth about $5. The ziplock bags about $ 0.60. The farm land on which it grew is about 25 square meters, worth about $55 to purchase, but costing at least three times this given the irregular fruiting, so say $165 minimum. Suburban land is worth much more per square meter. The labour took one hour to harvest and two hours to process, at minimum wage around $60 total. This gives a total cost of at least $225 to produce a product I could have bought for $100-200. So this shows that growing my own mangoes makes no sense financially, and would make even less sense for people living in suburbia where land is more expensive. The labour to pick and process was the largest component for me, and Australian mangoes are picked by migrant workers paid by the ton (and even then often exploited and underpaid) versus overseas labour that earns a tiny fraction of the local wage (hence the lower price for imported fruit). My sense that this tree wasn’t worth spending more resources protecting seemed about right.

The energy analysis is likewise very interesting. The 15 kg of mango flesh contains about 37 500 kJ of energy, enough to power a human for 3.7 days. The time equivalent energy investment of three hours picking and processing would give an equivalent EROEI (energy return on energy invested) of 30. Most sources say agricultural societies need an EROEI above 10 to be viable, so mango seems to have a positive role on the farm according to this. If mango was to provide all the energy a person needed in a year they would need to pick 1.83 acres of mango trees as productive as this one (though keep in mind this crop only occurs every 3 or more years, so in the longer term at least 5.5 acres would be needed). This compares to about 0.3 acres of paddy rice per person in preindustrial east Asia. On top of that this mango would need to be successfully preserved to feed the person day in and day out. This poor person would be trying to pick, process and dry 13 tons of mango flesh every three years in the space of a few weeks to survive (and then trying to stop it spoiling until the next crop arrived). Rice on the other hand is ready to store immediately if the weather is fairly dry at harvest.

I also harvested a similar amount of fruit from a neighbour’s tree. We drove a 6 km round trip, consuming about 0.72 L of petrol on the way. This fuel contained about 25 000 kJ of energy (with about as much consumed by the manufacturing of the car on top, though we will ignore that here). This means this mango harvest had an EROEI of a mere 1.5, though this is better than the industrial agriculture system which consumes 5 to 10 Joules of fossil fuel energy for every 1 Joule of food energy it delivers to people (EROEI of 0.1-0.2). Would I have walked the 6 km trip, carried the 30 plus kg of whole mangoes, discarded 10-20% of the bad ones, to get my 15 kg of highly perishable mango flesh?

This kind of rough analysis shows why fruit and veg based food systems that are sometimes imagined today are unknown in history. Humans need staple crops that provide a reliable source of energy that can be easily stored and transported. Fruit and vegetables are wonderful seasonal luxuries but people with a permaculture mindset will do well to not overlook the importance of boring starches.  Man cannot live on mango alone.

My little mango tree with the big bite taken out of its bark.

Dried seeds of a new strain of banana mango, waiting to be opened and sowed.

Young mango seedlings flushing with growth one year after transplantation. These were watered twice with dripper bottles until the summer rains arrived. This year’s transplants will get zero watering since it is already raining enough.

The new heritage strain of banana mango, showing deeper colour than my other type.

The young buckling helping with the harvest. You take the fruit and Ill mop up any leaves you knock down.