Plastic substitutes, Plastic-free gardening

The alternatives #2: Clay and coir

Clay pots

IMG_5043Probably 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)

coirpots_hairypotplantcoThe 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.

The Hairy Pot Plant Company stocks plants ready-grown in coir pots as well as the pots themselves, via The Natural Gardener.

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The plastics in your garden

There’s a huge range of plastics in common use in the garden. Here’s the breakdown:

PET1: Polyethylene Terephthalate: marked with a 1 on the triangle. Very commonly recycled, can break down when exposed for long periods of time to light or heat.

Used in: Practically nothing in the garden. It’s the stuff drinks bottles are made of and too unstable for most uses as it breaks down to easily to withstand sunshine and weather.

HDPE: High Density Polyethylene (Polythene): marked with a 2 on the triangle: doesn’t break down easily, resists UV rays and very heat tolerant, coping with -100 to 80C – one of the most common plastics used in the garden because of these properties.

Used in: most black, brown and green rigid plant pots; seed trays; the containers you buy pesticides, herbicides and fertiliser in; insect-proof mesh

How to avoid: Use biodegradable pots; use wooden seed trays; make your own pesticides, herbicides and fertiliser from the plants you grow; and I am still experimenting with alternatives to insect-proof mesh. Calico is looking expensive, but promising.

PVC: Polyvinyl Chloride: marked with a 3 on the triangle. Used in plastic pipes and irrigation. Most contain chemicals known as phthalates, helping the PVC to be more durable, flexible etc. But phthalates are very harmful to humans.)

Use in gardens: hosepipes

How to avoid: rubber hosepipe might seem a good alternative, but many are synthetic rubber which is basically plastic. Better just not to use a hose: use a metal watering can instead.

LDPE: Low Density Polyethylene (Polythene): marked with a 4 on the triangle. Single use plastics used in things like plastic produce bags and bin liners. It came along after HDPE and shares many of the same characteristics – so very safe in a wide range of températures and doesn’t Leach into the soil.

Use in gardens: Single-use packaging around mail-order items

How to avoid: Buy from nurseries and garden centres or find a supplier who doesn’t pack in plastic (easier said than done…)

PP: Polypropylene: marked with a 5 on the triangle. Used in products that require injection moulding like straws, bottle caps, food containers. Not as tolerant to heat as HDPE or LDPE, generally safe for use with food and the garden.

Use in gardens: Some more flimsy plant pots (eg seedling modules); Horticultural fleece is made from woven polypropylene.

How to avoid: Use newspaper pots instead of modules; wrap plants in hessian and straw instead; or just avoid growing particularly tender plants.

PS: Polystyrene: marked with a 6 on the triangle. One of the most widely used types of plastic, but one of the most harmful to the environment as it breaks down very quickly into very small particles, and tends not to last very long.

Use in gardens: Bedding plant trays and packaging for mail order plants

How to avoid: Raise your own bedding plants, or buy from a supplier who doesn’t use polystyrene trays. Buy from nurseries and garden centres or find a supplier who uses biodegradable cornstarch packing instead.

Polycarbonate: marked with a 7 on the triangle (this actually means any plastic other than those listed above – but usually polycarbonate or polylactide). Polycarbonate is the most harmful plastic we have ever created: proven repeatedly to leach BPA (Bisphenol A) – shown to cause reproductive problems in animals and linked to cardiovascular disease and diabetes in humans.

Use in gardens: Plastic non-breakable greenhouses and cold frames.

How to avoid: Use glass instead.