As someone who has been weirdly obsessed with growing things since I was a kid, I am always perplexed about how fearful beginners can be when it comes to gardening. This is probably why, when I ask nervous newbies about their first attempts, they invariably say they wanted to start with something manageable: a single plant in a small pot. The horticultural industry has ingrained this idea with glossy campaigns for beginners to . But here’s the kicker: growing in pots is actually far more likely to result in failure – and it is all down to simple physics.
It might seem like a trivial difference to human onlookers, but from the plant’s perspective, having its roots in a pot versus open ground can have a profound impact on two key determinants of its growth: water and temperature. The lower ratio of volume to surface area means plants in pots dry out faster than they will in the ground, as the smaller volume of potting mix is . This is particularly the case in containers made from porous materials, like unglazed terracotta.
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Similarly, a pot’s smaller volume means it heats up much faster in summer and is quicker to freeze in winter, creating fluctuations in temperature that plants like these pansies, pictured, may struggle to adapt to. This is why on really hot days, hanging baskets and window boxes can need watering up to twice a day, while the same plants in the ground may need it just once a week.
Even if you set up an automated irrigation system (and what beginner is going to do that?) there is another key reason why plant growth can suffer in pots. Horticulturists have known for centuries that restricting the growth of roots using small pots has a mirror effect on the plant’s size above ground. This has been the basis of bonsai culture since classical times.
Trials have shown that the effect can have and on plant health. Plants rely on their roots to take up the water and nutrients to fuel their growth, so restricting space has an overall impact on their vigour.
Finally, let’s talk nutrients. In healthy garden soil, microbes unlock minerals and other compounds beneficial for plant growth. In pots, the medium used tends to not be soil but substances like peat, which both contains far lower levels of nutrients and lacks the ability to support the microbial life that makes these nutrients available.
Moral of the story? For pretty much every aspect of health, growing in the ground will require fewer inputs from you and a more stable environment for the plant. So if you have failed at your first horticultural foray in a pot, don’t blame yourself! You were set up for failure. Try growing the same plant in open ground and thank me later.
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