It is an article that seems to come around every year: the promise that the average family can save money by growing their own fruit and vegetables. Whether they echo “dig for victory” wartime nostalgia or romantic pioneer spirit, the writers never really reference how they arrived at the stats they use. So can your average home gardener really compete on price against the economies of scale of industrial agriculture? Let’s crunch the numbers.
Say you want to start with one of those bucolic, wooden potato-growing planters you see in gardening catalogues. In the UK, these cost around . Given potatoes in my supermarket are £0.90 per kilogram, that planter would have to produce at least 83kg of spuds for me to break even, before we even talk about the cost of the seed potatoes, the growing medium, fertiliser, tools and water. Assuming you get similar yields per square metre as , a 60×60 centimetre container would only give you around 2 to 3kg per year. So at best, you would only just recoup your investment after around 27 years.
What if you dispense with the fancy kit and just shove some potatoes in garden soil? Well, given that saving potato tubers to start off new crops is in many countries to prevent the spread of plant viruses, you will still need to start by buying seed potatoes. In my garden centre these don’t come cheap, at about £9 per kilo. While it is true that for every kg of seed potatoes you buy, you can get a harvest of up to 10kg, that ultimately only reduces the cost to around the same per kg as my supermarket spuds. For easy-to-transport produce with long shelf lives, like potatoes, carrots and onions, it really is almost impossible to get the maths to work in your favour on a domestic scale, as efficiencies resulting from agricultural mechanisation make these so inexpensive to buy.
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However, when it comes to more delicate offerings, the reverse is often true. As these highly perishable crops tend to be laboriously (and expensively) harvested by hand, they can be some of the most costly to buy. And the three most expensive items in my supermarket produce section also happen to be the easiest to grow. Gram for gram, herbs like chives (pictured above) are over 50 times the cost of spuds and come from varieties that can crop for half a century from a single planting. Many other herbs like mint, dill and fennel are so resilient that much of the gardening advice is how to prevent them from taking over your plot.
This is also true for pricey salad crops like wild rocket, or arugula, which lives a secret double life as a common garden weed, and for delicate berries like raspberries and blackberries, whose plants’ rugged constitution doesn’t extend to their fruit. But these are, it turns out, the exception to the general economic reality.
James Wong is a botanist and science writer, with a particular interest in food crops, conservation and the environment. Trained at the Royal Botanic Gardens, Kew, in London, he shares his tiny flat with more than 500 houseplants. You can follow him on X and Instagram @botanygeek
For other projects visit newscientist.com/maker
