Archive for the ‘Tree Team and Propagation’ Category

Tree of the month: July 2015

Friday, July 3rd, 2015

Tilia oliveri, image credit Edward Parker

What is the tree of the month?
Tilia oliveri (Oliver’s lime)

Why is it tree of the month?
The beautiful foliage with a pale underside, along with the large flower bract make this species quite distinctive. Soon to flower, this is most definitely a seasonal highlight.

Where can I find it?
The champion grows on Specimen Avenue, whilst there are other mature trees in Acer Glade and on Holford Ride.

Dan Crowley, Dendrologist

Tree of the month: June 2015

Tuesday, June 2nd, 2015

Styrax japonicus snowbell tree credit Gina Mills
What is tree of the month?
Styrax japonicus, also known as the snowbell tree.

Why is it tree of the month?
An ornamental beauty, the white, bell shaped flowers which hang beneath the branches are not to be missed.

Where can I see it?
Specimens of varying ages grow in both the Old Arboretum and Silk Wood. One close to Savill Glade always catches the eye from Main Drive, where it grows alongside the also lovely S. obassia.

Dan Crowley, Dendrologist

Tree of the month: May 2015

Thursday, April 23rd, 2015

Acer amamiense

What is tree of the month?
Acer amamiense

Why is it tree of the month?
The new foliage flushes beautiful shades of purple. It really is a treat. The new growth is also rather hairy!

Where can I see it?
We have six plants. Three in 2050 glade, two around Savill Glade and one at the south end of Palmer Ride.

Dan Crowley, Dendrologist

> Find the locations of these plants using the Interactive Map

Tree of the month: April 2015

Monday, March 30th, 2015

Acer pycnanthum in autumn

What is tree of the month?
Acer pycnanthum – the Japanese red maple

Why is it tree of the month?
A rarity in the wild and less familiar in cultivation than it’s American counterpart Acer rubrum, it is going to flower for the first time here at Westonbirt!!

Where can I see it?
Close to Loop Walk on the north end of Holford Ride.

Dan Crowley, Dendrologist

Stuck between rot and a hard place…

Monday, March 16th, 2015

Deciding when to remove old trees is one of the hardest decisions we have to take here at Westonbirt. All of the arboretum’s trees are regularly inspected for safety reasons and we try to strike the balance between allowing old and valuable trees to remain and visitors’ safety.

As trees reach the end of their lives they tend to go into decline (known as senescence) and as managers we try to care for specimens through this process, for example by gradual crown reduction. However, we can only delay, rather than prevent, the inevitable. Sooner or later we have to say goodbye.

The time has sadly come to fell a magnificent giant redwood (Sequoiadendron giganteum) that has graced Main Drive since the Holford family started their arboretum in the mid-nineteenth century, as its health has been in decline for many years. We have taken the difficult decision to remove it following lots of close monitoring and some recent investigations. Although the decline of this specimen is fairly obvious, it can be tricky to get a clear picture as to what is actually happening inside a tree’s trunk.

The external signs of decay

The external signs of decay

To help us in this instance we recently arranged a specialist test on this tree with the Treetronic system, which uses electric current/voltage to investigate the internal properties of the tree. The result of the measurement is a two-dimensional map of the electrical impedance (EI) of the tree. Importantly, each tree species has a typical impedance (water/moisture) distribution, and to properly analyse the EI results, the operator should have a good working knowledge of how the subject tree species grows and how the water/moisture distribution may vary in different seasons.

As suspected, our results indicated a central column of dysfunction/decay, which corroborates the external characteristics. The resulting diagram for this tree revealed a high degree of decay (red areas), which matches the outer visual evidence. Based on past experience, we can assume that the decay also extends into the root plate, which would adversely affect the tree’s stability.

Graphic showing internal decay in red

Graphic showing internal decay in red

On a brighter note, we do have over 50 other giant redwood specimens throughout the arboretum, and we also hope to collect more wild seed later this year from western USA.

Finally, if a reminder were ever needed that our trees do not live forever and that we do need to manage older specimens in particular, then just a short distance away on Loop Walk you can still see the uprooted remains of a large Nootka cypress (Xanthocyparis nootkatensis).

The uprooted remains of a large Nootka cypress

The uprooted remains of a large Nootka cypress

This tree was being monitored closely due to decay in the base, but unfortunately fell during high winds over the Christmas period before we had chance to remove it.

Mark Ballard, Curator

Tree of the month: March 2015

Friday, February 27th, 2015

Illicium simonsii

What is tree of the month?
Illicium simonsii

Why is it tree of the month?
It is a lovely pyramidal shrub with small, pale yellow, fragrant flowers that are worth seeking out for both their look and scent. It usually flowers towards the end of the month, so keep your eyes peeled!

Where can I see it?
It can be found in both the Old Arboretum (close to Main Drive and Savill Glade (tree number 25.0799)) and in Silk Wood (Sand Earth (31.1424)).

Dan Crowley, Dendrologist, Westonbirt, The National Arboretum

>> Visit the Westonbirt Map to search for trees by name or tree number

Tree of the month: February 2015

Sunday, February 1st, 2015

Picea farreri
What is this month’s tree of the month?
Picea farreri
Farrer’s spruce

Why is it tree of the month?
Graceful form, glaucous (blue-ish!) foliage.

Where can I see it?
Sand Earth in Silk Wood, set slightly back from Willesley Drive.

Dan Crowley, Dendrologist, Westonbirt, The National Arboretum

The Wolfson Tree Management Centre: An Update

Friday, January 30th, 2015

Work is currently underway on what will become the new Wolfson Tree Management Centre. The new facility will provide all that Westonbirt’s expert tree team needs to manage the tree collection.

The foundations and floor slab are now complete for the new machinery store. The contractors have now started work on the drainage and completing the new yard.


This is a photo taken from the edge of the new yard marked out with a timber edge. Drainage channels form a boundary around the new building to protect it from heavy rainfall and to ensure any rainwater runs along the channels and pipes to a soakaway.


This is a photo of the first section of the new yard which has been finished. This area will become the tree team’s new vehicle wash down and fuel fill up point, their own a miniature fuelling station! The waste water and any potential spills of oil or diesel will drain along the new channel, where it is then filtered by a very large oil interceptor tank, see photo below. This tank holds any leaked oil and fuel which we can then remove safely.


The new yard and building floor slab have been created with a very high level of care and attention to detail although the brush finish across the site has been created by using just a brush and some rope!


Sophie Nash, Project Manager

A Wonderful Winter Walk… with one exception!

Tuesday, January 27th, 2015

Today I ventured over to Silk Wood to see how some of the Tree Team were getting on with essential tree safety work, which reassuringly was being carried out to a high standard as always.

I was also pleased to see that other team members together with volunteers had resurfaced parts of our rustic woodchip path network, using safely processed material from our very own on-site woodchip pasteurisation unit.

Brian Williamson credit to Charles Budd
I bumped into two of our independent coppice workers nearby, busy tending to the freshly cut hazel stools in one of their coups.

Large parts of Silk Wood have been managed for hazel coppice with oak standards over hundreds of years, and it can be a rare pleasure these days to see people managing such woodland in the traditional way.

If you look closely, you may even see the coppicers putting the cut hazel to a variety of different uses depending on the thickness of the stems.

I believe that we are very lucky to have wooded areas to enjoy at Westonbirt, as well as the contrasting open space of the downs and landscaped parts of the arboretum.

It was beautiful out in Silk Wood but I was very sad to find lots of discarded plastic dog poo bags and surprisingly even some abandoned bags full of dog waste and tied.

It’s in everyone’s best interests to keep the whole arboretum tidy, so that the magic of the place can be enjoyed by all.

But it is also a working environment and looked after by a small and dedicated team, and it is not very pleasant for them to stumble across dog waste during a working day.

I would kindly ask visitors to help us to look after the arboretum, by just popping poo bags in the bins provided.

Mark Ballard, Curator

A job well done

Friday, January 23rd, 2015

It’s always sad to say goodbye to a big old tree like the oak we felled earlier this week near to the restaurant.

A big well done goes to the Tree Team for the extremely professional way in which the felling of this tree was safely undertaken.

This was a well organised operation, with great care taken to ensure no damage to either buildings or people!

The team counted the annual growth rings as best they could and estimate that the tree was around 200 years old.

Watch this space to see another aspect of our ever evolving landscape take shape.

Mark Ballard, curator