The gardener's gamble

Here's a sticky one: what do horticulture and gambling have in common? 

On the surface of it, they're worlds apart. If you try to imagine any crossover, it is only in the lush gardens of a grand casino or the management of race courses. That said, both can become a dangerous obsession: ambitious aristocrats set out landscape plans they couldn't sustain, and Dutch tulipomania created an economic bubble that led to the crash of 1637. 

But there's another similarity I'm thinking of. Scratch the surface, and horticulture is much closer to gambling than we think, because there's something about the act of gardening that forces us to take chances. It's in its very philosophy, even before we put a seed in the ground.

Firstly, there's a thing called seed viability. Biodiversity International defines this as 'a measure of how many seeds are alive and could develop into plants which will reproduce themselves, given the appropriate conditions'. In other words, if you have a pumpkin seed, does it contain an embryo capable of becoming a pumpkin plant? 

I actually find this definition a little sloppy. It relies on you studying the seed only at a given point, so doesn't take into account the decline in seed viability over time. And without specialist equipment to see whether a seed embryo is alive, amateur gardeners are directly engaged in a game of probability. So for me, seed viability is the changing likelihood over time that a seed, given optimum conditions, will germinate. 

Take the humble Pastinaca sativa, or parsnip, for example. It has seeds with a notoriously short shelf life. If you sow 100 seeds in the first year, you might get 90 parsnips, but 100 of the same seeds the following year might only give you 25 parsnips, so the probability of success drops from 0.9 to 0.25. These aren't cold stats: you're involved in a game of risk and reward. Improve how you store the seed, and you'll raise your chances of digging white parsnipy gold in the Autumn of year two.

There's another side to the game, too. Some friends recently asked me to tell them what was wrong with their ailing mint plant. Its leaves were browning and the soil was dry. It was right next to the window and we had had a couple of scorching days: it didn't show any signs of pests or disease, and was just clearly unhappy with its living arrangements (mint prefers to be a little on the damp and shady side). 

'Will it survive or should we throw it away?' they asked. 

'Well,' I said, 'if you throw it away it definitely won't survive; if you don't throw it away, it might survive'. 

In geeky terms, where A = {The plant survives} and B = {You throw the plant away}, P(A∩B) = 0. You reap what you sow, but you can be sure you won't reap if you don't sow. It's a positive attitude to adopt in life, not just in your herb box: nothing ventured, nothing gained.

But it goes further: every interaction gardeners have is ruled by chance. You look at the weather forecast and don't water your plants because there's 60% chance of rain. You're taking a risk - if it rains, you've saved economic and material resources (money and water); if it stays dry, you've may lose your crop. What's more, in a world where climate change is likely to make weather patterns less predictable, we may find ourselves more often on the wrong side of the die. 

A drought-tolerant garden at Cambridge Botanic Garden

But it makes me wonder: could probability - perhaps even game theory - inform the way we manage our gardens as a way to increase resilience? Adopting a lusory attitude, could we ensure our gardens thrive and survive?

Food for thought.