20 November 2018

Bio-based alternatives to plastic plant pots

Hairy Pot Company selling hardy perennials and herbs, raised in coir pots made from coconut husk fibres

Plastic plant pots are often used once – to bring on plants from seed or transport them home from the shops – and then thrown away. While these pots are very convenient, such disposable items contribute significantly to plastic pollution. It is possible, however, to buy biodegradable plant pots produced from bio-based materials.

In recent years, plastic pollution has hit the headlines as a major environmental issue. While gardening is an outdoor activity involving organic material and natural products, the uncomfortable truth is that gardeners use a lot of plastic.

At the start of the 2018 series of the BBC show Gardeners World, presenter Monty Don acknowledged this. Talking about his own garden, which is used in the show, he said: “One of the things that has really horrified me looking at the garden over this winter is the amount of plastic that we’re using here, we have plastic pots, we have plastic seed trays, almost everything I buy is wrapped in plastic.”

Pots are one of the most common plastics in the garden. In the UK alone, it is estimated that around 500 million plastic plant pots are used every year. And a survey by consumer magazine Which?, found that the average British gardener has 39 plastic plant pots cluttering their shed, greenhouse or garage.

Of course, you can look after the pots, use them more than once, and eventually put them out with the recycling. But unfortunately, it isn’t quite that simple. They are often not easy to recycle, and worldwide less than 10% of plastic waste is recycled.

It is possible, however, to buy bio-based pots. These are made from fibrous bio-based materials such as wood pulp, rice hulls and cow manure that are pressed into the shape of a plant pot. Most are biodegradable and can be planted with the plant, or thrown in the compost, once finished with. Some – such as those made from rice hulls – are rigid and can even be used multiple times, over a few years.

One disadvantage of bio-based plant pots is that they tend to be more expensive than plastic ones. Currently, on Amazon.co.uk, for example, you can get 100 8 cm wood pulp pots for £13,99 (€15,62), while 100 similar sized plastic pots will cost you £10,88 (€12,15).

However, a recent survey by Gardeners’ World magazine, in the UK, found that 85 per cent of its readers wish to use less plastic, and 66 per cent would be willing to pay more for goods that reduce their plastic use. While research in the US found that people are willing to pay more for non-plastic pots. This suggests that there is an appetite for alternative pots, even if more expensive. But naturally, after more than 50 years of plastic pots, gardeners will be concerned about how well these alternatives work and possible negative effects on their plants.

Research on bio-based pots and plant growth is limited, but in 2015 a special issue of the journal HortTechnology looked at alternative containers for growing ornamental plants.

Two US studies compared the growth of different plants in plastic, bioplastic and bio-based pots – made from coir, manure, peat, rice hull, straw and wood pulp. One found that in greenhouses there was no difference in growth between plants in bio-based and plastic pots, concluding that bio-based pots were suitable alternatives to plastic. The other found no impact on plant establishment or growth when planted outside in bio-based pots, compared to plants that had been started off in plastic containers.

A research review also found that most trials had seen little difference in plant growth between plastic and bio-based pots, but there were a few exceptions. “In other research, plants produced in conventional plastic containers have greater growth,” the authors write. They suggest that this inconsistency may be due to increased water loss through the walls of bio-based pots – which could effect plant growth – and highlight a few trials that have shown that plants in some alternative containers need more water.

Derek Taylor certainly found that plants in bio-based pots require more watering when he switched his nursery business from plastic to coir pots 14 years ago. “One of the issues the retailers have with our pots is they take more looking after – because the water doesn’t hold in the pot so well, it leaks out all over the surface,” he explains.

Derek’s nursery, the Hairy Pot Company has been growing hardy perennials and herbs to sell to garden centres and similar businesses since 1984, but since 2004 they have been raising them in coir pots.

The pots are hand crafted in Sri Lanka using coconut husk – waste from local coconut farms. After being washed and dried, fibres from the coconut husk are pressed to produce a loose coir mat and then moulded to produce a rough pot shape. This is dipped in natural latex – to help hold the fibres together – and put through a much heavier press, to give the pot its final shape. The pots are then dried and trimmed. The final product is completely biodegradable.

When the company decided to switch from plastic pots – to create a greener product – they tested various alternatives, such as rice hulls, peat, miscanthus grass and coir. Derek says that it quickly became obvious that the coir pot was the right one for them. “The plants just did so well in them,” he explains.

“We’ve found that most plants have performed fantastically well in them, if anything they have performed too well,” Derek adds. “For the volume of compost we have in the pots we are getting quite a big plant on the top.” The hairy appearance of the pots was also an advantage. “You didn’t have to tell anyone it was more natural, or eco-friendly because it shouted it,” Derek explains.

Switching to coir pots has been tough though. Derek says that initially the business lost quite a few customers. Recently, however, there has been a surge in interest, as people have become more concerned about single use plastics.

While it would be difficult for a commercial nursery to switch to coir pots, due to the scale of their operations, for private individuals Derek says it would be pretty simple. “It is dead easy to grow plants in them,” he states.

Source: AllThings.Bio, 2018-10-29.

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