Plant Profile- The Spuds of Doom

There has been a surge of sudden interest in growing your own food in response to the current pandemic. Growing your own food is a slow process, as is the accumulation of the skills and knowledge needed: all the more reason to start sooner rather than later. It is also an activity that has given into the temptation to use cheap industrial resources to get faster and bigger results without stopping to consider if you are actually producing or consuming overall. If you are using more resources than you are creating then it is just another self-indulgent hobby.

Growing food profitably (and not just in terms of money, but also resources and labour) requires a careful assessment of the resources already in place. Firstly sunlight is a prime consideration. Without sufficient light the range of plants that will grow is greatly diminished and those that will tolerate shade will grow very slowly. Next is soil. Not all soils are great for growing food, though most marginal ones will grow a diminished range of varieties to some degree. The next consideration is water. Most Australians live in places that get sufficient rain at some time of the year to grow appropriate crops without irrigation. Water from the tap is becoming increasingly expensive and unreliable, a trend that is unlikely to change. Learning to grow seasonally in response to rain is a big advantage. The final resource consideration is plant nutrients. Most Australians currently dispose of the nitrogen, phosphorus and other nutrients they consume down the toilet. Urine is sterile and can be used without the disease risks that faeces poses. In a suburban space the density of humans is high enough that urine is more than enough to supply these essential nutrients, in fact excess application is a real risk in the limited space.

People in apartments in my opinion should not bother trying to grow food in pots on the balcony for any reason other than to learn a little of how plants grow and respond. The resources spent would be better used locating growing space in real soil or better yet focus on learning to cook from basic ingredients, buying vegetables in bulk from large markets and learning to preserve them with low technology methods. Access to basic ingredients is likely to remain for the foreseeable future while processed and imported foods will become more expensive. Cooking from scratch also greatly decreases food costs while improving health as well. Great adaptive responses to a health and economic crisis. Those in the suburbs with limited space should also be using their limited space and resources to grow highly perishable foods that are difficult to transport. Fresh herbs are the highest priority in this category since they are the most robust and adaptable to a variety of conditions of light, water and soil, can be harvested over a long time period, and can be used to turn otherwise bland meals of basic ingredients into something delicious. Next the leafy greens represent the best return on investment for much the same reason. I think of a lot of these crops as being somewhere between a herb and a vegetable. Parsley and basil are great examples, but rocket and endive are on this spectrum as well. These leafy crops are quick to mature, can be harvested as thinned seedlings early in the season, and have a long and flexible harvest season thereafter. Vegetables that are easily transported and stored like onions and pumpkins are better bought in bulk.

People living further outside of suburbs with more space on their hands might be tempted to grow staple crops. These are the plants that produce the calories that fend off starvation and make up 50-80 % of the energy a person consumes. In the industrial age where mechanised grain farming drove the grain price to a tiny fraction of a person’s income the importance of these crops became largely invisible. If anything we began to hate them as overconsumption led to obesity in many for the first time in history. When starchy staples are dried down they seem so small and insignificant compared to vegetables, but veggies are made up predominantly of water and fibre. The difference in price between rice and vegetables in the shops also encourages people to overlook their importance. In the short term those with limited space are much better off growing perishable vegetables, but where does that leave growing staples? A lot of home vegetable gardeners respond when asked about hypothetical end of the world scenarios simply say “I will just plant a few more potatoes”. Potatoes have the advantage over other staple crops in that it can be grown and prepared using nothing more complex than a shovel and paring knife, unlike grains which require complex harvesting and processing tools and techniques. It might be interesting to look into the idea of growing your own potatoes as a staple in more detail.

World potato yields range from about 20 tons per acre in the USA to 2 tons per acre in the developing world. Potato is a gross feeding crop that responds very strongly to added fertility and protection from pests and diseases, hence the wide range of values. Home gardeners using a lot of inputs can get close to the upper range in a good year, but during bad years often fall down to the lower end. Humans need about 10 000 kJ per day, and potato contains 2800 kJ/kg, meaning a single person needs 3.5 kg potato a day, 1300 kg per year, grown on 0.065 to 0.65 acres assuming one crop per year. The lower end of the range is about 260 square meters, easier to imagine as a 16 x 16 m square. The average Australian suburban block is about about 550 square meters. With about half that area suitable for growing potatoes in the best situations the average suburban block could support one person per year eating nothing but potatoes assuming they achieve the best high input dependent level of cultivation (and never have a bad year). As such suburbia can never be self-sufficient for food (let alone firewood to cook it). Suburbia is only viable so long as imported food is cheap and reliable, cities even less so. Realistically a human wouldn’t eat nothing but potatoes, though it is one of the few foods that potentially could be the sole source of nutrition without unavoidable deficiencies. Other home garden crops yield about the same or lower calories so diversifying the species mix won’t fix the issue.

This is usually where all the bargaining of suburbanites begins. They could double crop in places with a frost free climate for 8 or months. That would increase the amount of fertility the site would need imported to remain productive, and accelerate the development of nutrient imbalances that would take constant laboratory testing to manage. Even cropping once every year would lead to exhaustion or imbalance. They could grow vertically in containers, but this would require vastly more infrastructure than growing on flat land and eventually lead to light access being limiting. An expert gardener could combine crops but potato production drops steeply once they are more than lightly shaded. And higher outputs means higher inputs, with an increasing risk of nutrient imbalances. The bottom line is that the suburbs are completely dependent on access to cheap and reliable food grown elsewhere by oil powered machines for robust staples or underpaid labour and refrigerated trucking for most delicate and fresh foods. People with limited space should focus on growing delicate vegetables for the price and quality advantage and learn to cook with and store store bought staples while they are still affordable. Maybe grow a little potato to learn some of its habits. And beyond that a plan for leaving suburbia before food becomes inaccessible at any price would be prudent. Australia and the USA are lucky in that we have enough land for people to spread out at least in theory. Other parts of the world have much more difficult challenges ahead.

After all this preamble I should probably tell you how I grow potatoes. They are somewhat of a marginal crop in the coastal subtropics. The usual routine starts with seed potatoes in the autumn. The crop is frost sensitive, but also dislikes hot weather in summer. As such a crop can be planted in late summer to mature in the late autumn or early winter. This can then be replanted in the late winter to harvest in late spring. The autumn crop has the best conditions with cool nights and warm days and the soil is usually moist from late summer rains. The spring crop is more variable since a drought at this time of year will diminish the yield considerably. Last year the spring crop failed when we had virtually no rain from late winter until late summer. Many of the planted tubers survived this spell in dormancy and started growing this autumn. If I had started irrigating this spring crop then suddenly stopped due to running out of water the entire stock would have been lost. This highlights what is the greatest weakness for potato in my climate- where do the seed potatoes come from? Most people simply buy them when they want to grow a crop. This means relying on the varieties you want being in stock (and being virus free). Southern potato growers normally sell seed potato in late autumn, causing subtropical growers to miss the ideal planting time. Storing your own seed potatoes is difficult in the subtropics since they only remain properly dormant under cool conditions. Refrigerator space is expensive and limited. Over summer at room temperature the tubers shrivel and weaken, even under dark conditions. Humidity must be kept low enough to prevent sprouting, but not so low as to cause shrivelling. As it turns out the autumn crop at the best time of year often starts with substandard summer stored seed potatoes, and the spring crop at the worse time has the best quality seed potatoes. To grow a useful amount of potatoes takes a few years to build up seed potato stocks, but they can be lost in a single season if conditions turn bad.

Potatoes are an excellent crop to plant in new ground. Since it is beneficial to continue to hoe soil up around the growing plants it is fairly compatible with moderately weedy soil since you can weed and hill at the same time. They also produce well on fallowed ground such as recently killed lawn and pasture with little added fertility. Killing the pasture is often a difficult step. I cleared a large area of thick kikuyu grass with glyphosate toward the end of our summer drought. The tender hearted purists out there might be clutching your pearls, but I think glyphosate is great, with a few caveats. The toxicity is a complete non-issue for me. The petrol in your car and the soot that blows out the exhaust pipe are potent carcinogens and toxins, plus do people with the longest life spans in history really deserve to get too upset about a 5 % increased risk of cancer when they are 80 years old? The issues I have with it are a bit different. The first one is that it doesn’t do what people want it to do most of the time, namely “get rid of weeds”. The weeds come back usually forever if glyphosate is your only tool, though selective hand spraying can gradually give other weedy species the upper hand. Glyphosate is however great for the initial kill of dense pasture if it is going to be hoed afterwards so it is a once only job. The other problem is that glyphosate may not be accessible forever, either due to changes in legislation due to safety worries or more likely as we have recently seen due to supply chains that snake around the world being interrupted. It is mostly made in China now. In this situation my alternatives were solarising with black plastic (which wouldn’t scale over the area, and would take so long that I missed my planting window) or manual removal with a mattock (which would have taken all my time from other commitments and left my joints a wreck). Ideally I would have moved my geese into the space last spring but the drought worsened fox attacks so I needed to move them to safety. Mulching and paper work in principle but the scale was too big and the mulch would need to be imported by oil powered machines, and would then slow down planting as I tried to punch through it. Glyphosate was the best tool on offer. I applied it very lightly to cause a 60-70 % kill, then went back and spot sprayed parts I had missed. This ensures the minimal amount is used but leaves a little regrowth to manage later. The dead kikuyu sod makes an excellent weed suppressing mulch itself. If allowed to rot just the right amount it is easy to cut through with hand tools but dense enough to slow down annual weeds. I sprayed a bit late so the sod was still hard work to plant into this time, but nothing compared to living kikuyu.

Planting the potatoes was pretty simple. I used my hoe to clear a row of dead grass and weeds to sit the seed potatoes along. A small handful of aged chicken manure was placed between them. Larger tubers the size of a chicken egg were about 30-40 cm apart, smaller ones as close as 10 cm apart. I only had a small number of seed potatoes from my mostly failed spring crop during the drought and the main purpose of this planting was to build up numbers of some new varieties. If I had plenty of seed potatoes and was maximising total yield I would put them 20-30 cm apart. I also hoed about 20-30 cm wide to one side of this row of seed potatoes. This cleared the soil of debris so I could use the shovel to dig out slices of dirt about 5-10 cm thick that were then flipped up on top of the waiting seed potatoes. You can dig bigger chunks of dirt, but lifting them takes a lot more effort since they don’t stick to the shovel as easily. They also are too thick to cover the seed potato reliably, tend to roll away, and the seed potatoes have a harder time growing through them. Leaving even dead grass in the way results in a shovel blade clogged with grass and mud. Even still it is worth clearing the hoe and shovel blade regularly with a whack on the ground or if that doesn’t work with your boot or fingers. I leave a bit of loose soil in the trenches to dig up later once the seed potatoes start sprouting. This is useful in case you didn’t quite cover them first time. Later when the crop is more mature I hoe up the sharp edges of the trenches over the plants. The weeds normally don’t grow where the potatoes are planted since surface weed seeds are covered with weed free subsoil. The trenches are fairly weed free as well since they are subsoil. Only the shoulders of the trenches get weedy, and usually just in time for them to be hoed over the central crop later. In 3-4 months the tops die down. If the weather is dry I wait a few more weeks for the tubers to season, improving storage as their skins thicken somewhat. If the weather is wet I usually dig up tubers as the last life in the stems disappear to avoid rot. Planting tubers under slices of subsoil makes harvesting easy since the tubers will be wedged between the undisturbed subsoil underneath and the moved soil above. I can often harvest without using any metal tools by just flipping over slices of dirt, greatly reducing the number of damaged tubers. I get a few more green potatoes if I neglect to hill up the plants, but they make great seed potatoes for the next crop. You usually need to keep about 10 % of your crop as seed potatoes since spuds normally achieve a 10 to 20 fold increase in weight during a good growing season.

The history of the potato is worth reflecting on as well since it reveal so much about our modern world and its predicaments. Potatoes were domesticated in south and central America over thousands of years, drawing material from dozens of highly distinct wild species that still grow there today. These plants were brimming with bitter toxins that the native people learnt to detoxify. As they were domesticated varieties with larger tubers and lower levels of toxins were selected, often from hybrids between wild species growing together to make entirely new types. The best of these potatoes were transported by Europeans back to the old world. Initially they were regarded as poisonous novelties. I wonder what it was like being the first person who did a little research, ignored the advice of everyone around them, and decided to try eating them. Who were the first family that made potato a regular ingredient in their diet and made the difficult journey of changing their food culture? Once its value was established the potato spread rapidly across Europe as a crop. It produced more useful food than grains, allowing peasant populations to increase significantly. It was also easier to hide from tax inspectors, and more difficult to transport even if they found it, leaving more food for the common people. Their numbers swelled to record levels but then a disease from the new world found its way to Europe and potato blight swept the region, a cruel mirror image of the small pox and measles that wiped out the human populations of the Americas. Peasants starved, leading to one of the greatest human migrations in history and forging the identity of the fledgling United States of America. Blight resistant varieties were well known in its place of origin and eventually spread to the old world, returning the potato to its valued position.

History has a tendency to repeat itself. In a way we are lucky that the potato as we know it is a marginal crop here in the subtropics. Its bounty is a treacherous one as it can be taken away as easily as it is given. I am experimenting with growing diverse potatoes from their true dust like seed and exploring wider genetics but suspect they will only ever be a marginal crop here and not a true staple. A wider genetic base decreases the chance of an event like the potato blight wiping them out one day, and their tiny seed are easy to store for many years unlike the disaster prone seed tubers. Instead of the potato it seems more likely to me that other crops waiting in the wings will become our starchy staples on the subtropical coast. Staple crops need to be both productive and reliable to work and my preliminary trials have shown arrowroot (Canna/achira) and winged yam (Dioscorea) fit the bill. Both of these are commonly grown as sterile clones, propagated by division just like the first potatoes in Europe, resulting in a genetic monoculture that awaits a single well adapted pest or disease to wipe out the whole population. Both crops contain a much wider genetic diversity waiting to be explored. That is now my primary focus here on the farm, along with wondering what a society built upon them might look like in a few centuries time.

Laying out seed potatoes and chicken manure in a row cleared in the dead grass.
Digging up slices of dirt to cover the seed potatoes.
A large mass of Queensland arrowroot on the edge of my potato bed. No issues with seed tubers dying during storage with this crop.
Multiple finished rows with solarising in place to make the next beds easier to plant.
A row of kipfler potatoes that emerged after sleeping in through the spring and summer drought. Oddly these very lightly buried tubers in horrible looking soil survived better than those in fluffy and richer looking soil.
A small crop of seed grown diploid potatoes, closer to the original wild species. I’m not convinced they are better adapted to our local conditions than commercial varieties, but being able to save true seed is nice.
Potato harvest in between dirt slabs.
A few weeks worth of spuds to keep the wolves of hunger at bay for a while at least.

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