This is our second story about plants which have the potential to make a contribution to net zero, by:
- removing carbon from the atmosphere – all plants do this but some are much more effective than others;
- replacing more carbon intensive materials – without mining or chemical processes;
- improving soil health, water retention and biodiversity.
In our first article we looked at Miscanthus (elephant grass), now being grown as a feedstock for renewable power stations. Now we turn to Paulownia, another fast growing plant being trialled in Suffolk.
What is Paulownia?
Paulownia is the fastest growing deciduous tree known, producing its first timber crop in 6-7 years. Although it is native to warmer climates, hybrid versions which thrive in Northern Europe have now been produced. These absorb ten times as much CO2 as ordinary mixed woodland, and can grow to 8 metres in five years, producing as much timber in 10 years as Sitka Spruce does in 35, and Oak in 55.
Paulownia can be coppiced, which means that when the mature timber is felled, it regrows from the stump. As a result, much of the carbon it sequesters remains locked in the ground. This also makes it an attractive financial prospect for the landowner, who can harvest saleable timber quickly and repeatedly over more than 30 years, without having to replant.
Because it grows fast, Paulownia produces straight, high quality, lightweight timber, hence its nickname “the aluminium of the timber world”. It is very resistant to rot, and a good insulator against heat and sound. In Japan it has long been highly valued for furniture, light construction and specialised uses like musical instrument making.
Unlike evergreen conifers, which create permanent dark shade, where nothing grows, Paulownia sheds its leaves every year. The decaying leaf litter enriches the soil and combines with the light to allow plants to grow, promoting biodiversity, and providing homes for a wide variety of birds, wildflowers, insects and small mammals.
In conventional arable agriculture, soil quality is eroded every time the ground is ploughed, and this is even true of traditional forestry, where old timber is cleared and ground disturbed for replanting. In a Paulownia plantation there is no ploughing, leaving the soil to develop naturally, building structure, supporting worms and other natural organisms, and improving its ability to retain water.
First UK projects starting in East Anglia
Until recently Paulownia has only been grown in the UK as an ornamental plant. But in the first large scale development of Paulownia in the UK, in 2022, the Euston estate in Suffolk planted 195 hectares on land formerly used for arable crops. This is 10% of the estate’s arable land, and complements their 600 hectares of native woodland. The plantation will help the land to recover from the depletion inflicted by many years of intensive agriculture. The space between the trees has been seeded with native grass, wildflowers and legumes to boost biodiversity and attract insects and birds. The arrival of owls and kestrels for the first time in 2023 confirms the return of small mammals. The potential for grazing sheep and poultry is being explored.
Following successful planting on the Euston Estate in 2022, Carbon Plantations, the company behind the project, have started further developments totalling over 250 hectares on four sites in West Norfolk.
Carbon Plantations aim to plant 2 million trees over 5,000 hectares in the next five years. This will lock up 5 million tons of carbon over the next 35 years. To support diversity, 15% will be native woodland trees.
Preliminary discussions with timber companies suggest that there will be healthy demand for the timber when the first crop is harvested.
The Paulownia is an unusual looking tree. If this experiment works we can expect to see more of it. In some places it may change the look of the landscape, but its impact on the environment may be bigger.