Probably the one type of biodegradable plant pot we’ve all used at one time or another, clay pots have a fine pedigree: they were the go-to pot of choice for all Victorian estate gardeners, and remain the benchmark for classy gardens everywhere.
What is it: Clay pots are made of baked clay – that’s the stuff you get out of the ground, so about as natural as it gets. As old as the hills, the ultimate in traditional gardening, they look wonderful and last for ages if you look after them. But they are heavy and clumsy gardeners will struggle to keep them in one piece.
How long do they last: Theoretically, forever; you can reuse clay pots year after year for generations. They are more robust than plastic pots, in that you can strim a clay pot without it getting shredded; but if you drop one, you’ve lost it.
How are they made: You’ve seen Ghost, right? You know the pottery scene? (of course you know the pottery scene; it’s the only one anyone remembers from that movie). That’s basically the same for plant pots. Except possibly minus Patrick Swayze. They are made, by hand, from clay, on potters’ wheels, then fired in a kiln. You can watch a rather lovely video of US master potter Guy Wolff making terracotta pots here.
Terracotta – literally ‘baked earth’ – just refers to pots made of unglazed, and therefore porous clay (as opposed to ceramics, which are glazed).
Cost: Middlingly expensive, at about £1 a pot for 11cm diameter; slightly cheaper from reclamation yards where you can get lucky and pick up boxes of second-hand clay pots relatively cheaply.
Also available as: Rhubarb forcers, plant labels, plant saucers, pot feet
Pros: Re-usable and long-lasting; heartbreakingly lovely to look at, the stuff of fantasy gardens everywhere. They age beautifully, too. Available in every possible size and shape, and readily available too; these are the one type of biodegradable pot you can be sure to find in a standard garden centre. In my experience, plants like clay pots and seem to grow better in them: I think this may be because their porous nature allows the roots to breathe a little better. They dry out quicker than plastic, but re-wet more thoroughly as the pot absorbs water as well as the plant, so you don’t get water running down between rootball and pot and draining out at the bottom without wetting the roots. There are many UK based manufacturers, so they don’t have to travel far to get to you; though watch out as the cheaper versions seem to be made by a company called Spang, based in Germany, so are imported and so have a higher environmental cost.
Cons: Heavy, and easily broken. Pricey, especially online mail order as the postage costs are high for heavy items. The firing process – 1000 degrees for 18 hours or so – means that even though they are produced locally so don’t have a high mileage, the carbon footprint of clay pots is still pretty high.
Stockists: Widely available from garden centres, reclamation yards and garden equipment suppliers online.
UK-based terracotta pot specialists include Yorkshire Flowerpots and Whichford Pottery . Both do a ‘garden essentials’ range, but expect to pay more; there’s a good reason, too, as these are superb and very beautiful pots, and a cut above your bog standard potting shed fare.
Coconut fibre (coir)
The second most commonly found biodegradable alternative to plastic after clay; a single-use biodegradable which the plant roots can grow through, so you plant it along with your seedlings. It’s also made from what would otherwise be a waste material. Unfortunately, because it must be imported from south Asia, it comes with quite a high environmental cost.
What is it: Coir is a by-product of the coconut industry. It’s that fibrous, hairy stuff you find on the hard shell of a coconut, a mix of lignin and cellulose, and it’s extremely useful stuff: it’s also used in ship’s rigging, matting (mainly door mats) mattresses and potato sacks. It is, unusually for biodegradable materials, relatively waterproof which is what makes it such a popular product in horticulture.
How long do they last: Up to 12 months above ground before they go ‘hairy’ and are best planted in the ground. There they take a few months to biodegrade.
How are they made: Fibres are stripped from the coconut then softened in water, then mixed with latex, the sap from rubber trees, before being moulded into pots.
Cost: 50 9cm pots for £11 (but need to buy new each year)
Also available as: Hanging basket liners
Pros: Easy to re-wet as absorbs water easily. Available in every size from Jiffy propagation modules to large pots. Can be planted out in the garden without removing from the plant, avoiding root disturbance.
Cons: Coir has a high environmental footprint as it must be shipped from coconut-producing countries like India, Sri Lanka (between them the producers of 90% of the world’s coir supplies) and the Philippines, with all the carbon emissions that entails. And because these pots are not meant to be removed from the plants but are planted out with them, you have to buy in a new supply each year. Commercially, coir pots are often sold wrapped in plastic.
Stockists: It is surprisingly difficult to find larger coir pots. Small ones – propagation modules and pots up to 8cm – are readily available and the biodegradable pots you’ll most often find in garden centres. But I don’t use 8cm pots; I jump from modules to 10cm as I’ve found they need less watering, and anything below 8cm I can make myself at home. I did however find two UK sources for larger coir pots:
Green Gardener sells coir pots in three sizes, up to 16cm diameter.