Giant sequoias: World’s largest trees ‘thriving in UK’

Giant sequoias – the world’s largest trees – are thriving in the UK and are now even outgrowing those found in their native range in California.

Giants were first brought to the UK around 160 years ago and a new study suggests they are growing at a similar rate to their US counterparts.

There are approximately 500,000 trees in the UK compared to 80,000 in California.

However, they are still not that high. In California they can reach 90m in height, but in the UK the tallest is 54.87m.

But this is because the introduced trees are still very young. Giant redwoods can live for over 2,000 years, so there’s still plenty of time for the UK’s trees to catch up

“Half a million trees is quite a lot to fly under the radar until now, but when you start looking for them in the landscape and collect these data sets, you realize just how many there are,” said Dr Phil Wilkes, one of the authors of the study from the Botanic Kew Gardens at Wakehurst in Sussex.

Giant sequoias (Giant sequoiadendron) were first brought to the UK by the Victorians. They are the ultimate botanical status symbol, usually planted on the grand estates of the wealthy.

Today, some form wide avenues, while others stand one or two at a time. But they’re easy to spot: their dense, cone-shaped crowns stand proud of everything around them.

To assess how these towering giants are adapting to their UK home, scientists selected a sample of nearly 5,000 trees for study at Wakehurst, Benmore Botanic Gardens in Scotland and Havering Country Park in Essex.

They used laser scanners to measure the heights and volumes of some of the trees – also a way to weigh the trees without cutting them down.

The researchers found that the trees grew as fast as giant sequoias in their native home in the Sierra Nevada mountains. The UK climate seems to suit them, says Dr Wilkes.

“Where they grow in California is cooler and wetter than you would normally imagine California to be,” he explained.

“And we have a fairly similar climate here – it’s very humid and they need moisture to grow.”

Scientists have also looked at how much carbon dioxide trees absorb – trees absorb and store the greenhouse gas, and planting more trees can play a role in helping tackle climate change.

The researchers found that because of their large size, giant sequoias can hold large amounts of carbon dioxide in their wood—though not as much as their US counterparts.

The trees at Wakehurst, which are around 45m tall, have around 10 to 15 tonnes of carbon stored in them, Dr Wilkes explained.

“But compare that to the largest tree in California, which has about 250 tons of carbon, and they’re pretty small. But you know, these can get so big.”

Scientists involved in the study are quick to point out that planting giant redwood forests would not be enough to significantly reduce the amount of carbon dioxide in the atmosphere. But these majestic giants can play a role in a mixed forest plantation with a variety of other trees, both native and imported.

In California, natural wonders are threatened by climate change – they are not coping well with hotter, drier weather and more intense wildfires.

So could the UK become their new home?

In an avenue of trees originally planted as a front entrance to a now-derelict estate in Havering Country Park, University College London’s Prof Matt Disney says he thinks it’s more than possible.

“Climate-wise, it’s likely that they’ll have a less stressful existence here than in California,” he said.

Although he pointed out that conditions are also changing in the UK with climate change.

Giant sequoias are planted as saplings across the country, often by local governments in public parks or recreation areas.

Prof. Disney says they have a long life ahead of them and won’t stay small for long.

“They grow very fast and get big. Once they reach around 60m they will be the tallest trees in Britain and then they will continue to grow,” he said.

However, although the trees are doing well in the UK, there is little chance of them taking over our native woodlands any time soon – they don’t breed here as they need very specific conditions to set seed.