Arboretum team blog

Luscious leaves

Trees display an array of vibrant colours at this time of year. Here's my pick of some of the best to look out for:
 

Images: Vitis leaves (left); maple leaves (right)

Images: Diospyros leaves (left), Parrotia leaves (right)

Images: Quercus coccinea leaves (left), the conifer Psuedolarix amabilis (right)

Fabulous fruits

There is a wonderful show of autumn fruits this year: some are edible for us, such as the hazel and sweet chestnuts, but many more are palatable for birds and mammals. I'm sure that for most people, the prime autumn fruit is the blackberry.
 

Image: Blackberries - a favourite autumn fruit

However, there are many fruits from around the world in our collections and now is the best time to see them. The fruits of the ash, called ‘keys’ because they resemble bunches of keys, the Osage orange (Maclura pomifera) whose fruits can be as big as tennis balls, and the smelly fruits of Ginkgo, are just a few to watch out for.
 

Images: Ash "keys" (top left), Osage orange (top right), Ginkgo biloba fruits (bottom)

Keep an eye out for the Sorbus fruits as well - especially the Kew hybrid with its white and pink contrasting fruits.

Images: Sorbus x kewensis fruits (left) and Sorbus forestii fruits (right)

- Tony -

Well this is one of the strangest autumnal seasons that I can ever remember. It started early in September, with cool nights without a frost and high day temperatures with moisture in the ground. Everything was looking good for a timely fall with bumper leaf colour, but that all ended in early October with an incredibly hot week where we saw record day and night temperatures reaching about 29°C during the afternoon.

This has confused many plants and suddenly they think they are in spring again with many species flowering for a second time this year. The hollies on Holly Walk are flowering better than they did in May, which could mean no fruit next winter. 
 

A holly in flower
 

Best fruiting season in memory

With the warm, dry spring this year, however, I have to say that this is the best fruiting season in memory, with the fallen acorns and beech nuts covering the root plates of mature trees in such quantities that they crunch under foot as you walk across the grass. 
 

Acorns covering the ground
 

This weekend I drove back home to Twickenham from Cornwall along the A303 where hawthorns (Crataegus monogyna) along the hedgerows were thick with their red haws in huge quantities and sloes creating a matt blue haze through the leafless thickets of Prunus spinosa along the roadside.

Highlights at Kew Gardens

Back home in Kew Gardens, the displays of fruit in the arboretum are impressive and must not be missed this year. I love the North Canal beds on the location between the Mediterranean Garden and the Temperate House where you don’t have to walk far to see some unusual fruiting trees and shrubs.

The North American osage orange (Maclura pomifera) has unusual heavy green, brain-like fruits, but be careful when handling these as they ooze a sticky, white milky latex sap when damaged. Both male and female trees are needed for a good show of fruit. 
 

Osage orange (Maclura pomifera) fruiting

Close by are the persimmons in the ebony family, Diospyros virginiana from south-east USA with small, golden, tomato-like fruits and the date plum (Diospyros lotus). Look out for the edible “kaki” (Diospyros kaki), the Chinese date plum, which will ripen to a rich golden yellow, if we get some sunshine before the frosts. 
 

 
Diospyros virginiana (left) and Diospyros lotus (right)

Despite the flowering confusion with the hollies, some have really excelled with the fruiting, including one species that I collected in Sichuan, China in 1996. It has one of the longest scientific names, Ilex fargesii ssp. fargesii var. fargesii. 
 

Ilex fargesii ssp. fargesii var. fargesii in fruit

One of the most bizarre-coloured fruits are those of Decaisnea fargesii, sometimes known as dead man’s fingers as they look like swollen fingers in a strange most un-natural violet colour. 
 

Dead man’s fingers (Decaisnea fargesii)

Strange smells

If we could have touch and smell on the computer, Viburnum opulus var. xanthocarpum has one of the most vile-smelling fruits when crushed, a smell that is hard to describe. But probably one of the worst smelling fruits, especially when over-ripe, are the golden fruits of the Chinese maidenhair tree (Ginkgo biloba), which you will find on the female tree on Pagoda Vista at the Palm House end.
 

The vile-smelling Viburnum opulus var. xanthocarpum
 

In the Rosa species beds, the yellow hips of Rosa roxburghii are covered in short bristles and have a lovely scented aroma when crushed (if you don’t mind the bristles that is!). 
 

Rosa roxburghii

The weather is due to get cold again by the end of the week, so winter is likely to be with us soon. This could mean the end of what was promising to be a bumper fall colour - but the best fruiting autumn.

- Tony -

Autumn is a wonderful time in Kew’s Arboretum. Some of the deciduous trees, shrubs and climbers are changing into their autumn hues: wonderful shades of yellows, oranges and bright reds, with many colours in between. The colours can vary from year to year and are down to a number of factors, but mainly to weather and day length. Warm sunny days produce lots of sugars in the leaves and it is these that help produce lots of anthocyanin pigments, which make the red and purple hues. The yellows and oranges are from the carotenoids, another pigment which is always present in the leaves, and so these colours are constant in most years. As the day length shortens the leaves are cut off from the tree by what is called the abscission layer, trapping the sugars in the leaves, and as the chlorophyll disappears we are left with the wonderful autumn leaf colour.

What type of weather makes the best colour?

Warm, wet springs with good summers, late summer sun, and cool autumn nights produce the best colour. With October and November generally being the best months, this year seems a little early as the following photos show. This is possibly due to the hot dry spring we had.
 

Fraxinus americana 'American Ash'

Images: The coppery tones of beech are always a wonderful sight (left), and the stunning red of Liquidambar (right)

What else to look out for in Autumn

Fungi are also a wonderful sight in the autumn, and grow all over the Arboretum so be sure to look out for them over the next few months too. Here are some that can be seen now.
 

Images: Puffballs and honey fungus (left) and honey fungus(right)
 

There are still a few bulbs of the large flowered Colchicum autumnale, which will flower for a few weeks yet, as well as the true autumn crocus (Crocus speciosus) and the lovely small purple flowered cyclamen under some of our mature oaks.

Cyclamen hederifolium under an oak tree

Finally, there's more than just the plants, trees and fungi to see... Ivy is one of the last nectar and pollen sources of the year. On warm autumn days butterflies and bees will cover plants for a final feed.
 

Bee and comma butterfly feeding

- Tony -

Related links

• Discover trees and fungi this autumn at Kew
• Find out more about trees
• Visit Kew this autumn
• Experience the Xstrata Treetop Walkway
• Read about Kew's champion trees and fabulous fungi in the new issue of Kew magazine

The Arboretum at Kew Gardens has links and involvement with many botanic gardens around the world. Recently I visited the Gibraltar Botanic Gardens, which I have developed personal links with over the last ten years. When I'm out there I often research Mediterranean plants in their natural habitat and take part in seed collecting trips for Kew' s plant collections.

Entrance to Gibraltar Botanic Gardens and a mosaic map

The Gibraltar Botanic Garden has recently recruited a new plant propagator, Chris, who has just returned back to Gibraltar from Kew. Whilst here at Kew she shadowed some of the propagators, including Andrew Luke who runs the woody plant nursery in the Arboretum. The changes Chris has made in the nursery since my last visit to Gibraltar are already plain to see. I took some seed and plant material over with me for their collections and use in the new rock garden they are creating.

Building the new rock garden

I also took the time to drop into the gardens to catch up with friends; the Director John Cortes, Jon Hammerton who moved from Kew's Arboricultural Unit to the Gibraltar Botanic Gardens three years ago, and I was also joined for a day in the field by Keith Bensusan, who is in charge of research and collections there.

Keith, Chris and Jon behind-the-scenes at the Gibraltar Botanic Gardens

Viewing species in the Gardens

During my recent trip I was mainly looking at wild Narcissus which are a great interest of mine.

Narcissus in the wild - Left: Narcissus jonquilla Right: Narcissus cuatrecasasii

The weather was great, dry and sunny, and apart from the seven species of Narcissus I saw, there were some early orchids and sand crocus (Romulea clusiana) too.

Left: Barlia robertiana in flower, Right: Romulea clusiana in flower

I also saw heathers and many legumes out in flower, including the wonderful honey scented Coronilla valentina.

Coronilla veluntina in flower

Many of the plants collected from Gibraltar and Spain can be seen growing in Kew's Mediterranean Garden.

- Tony -