Thorp Perrow Arboretum

Geoff Appleyard Memorial Tree Walk

Friday 6th September 2024

Leader: Graham Heffernan

Graham led a visit here last year, but there was so much to see, it warranted another visit. As was the case last year, Group funds were used to offer a heavily subsidised entrance fee for members. Graham had selected some trees he wanted to show us, with our route today taking us to the northern and eastern parts of the site. As always, Graham was a wealth of information and we were most grateful for all the preparation he had done.

While Bradford Botany Group field meetings are usually focused on native or self-sown wild plants, the Group’s annual tree walk seems to have become an exception. Ordinarily, I would sooner explore a more natural habitat rather than a highly manicured garden, however, long established arboretums, such as Thorp Perrow, can be a great place to compare similar species, and can allow us to see plants that would be difficult to see in the wild. Some plants are so rare in the wild that arboretums are, sadly, their last refuge. Below is a description of some of the plants we saw today. Where known, I have given the Arboretum tree-number.

On route to the target species, we passed some of the species seen last year such as Cornelian-cherry (Cornus mas) Z210, with it’s tart red berries, Incense Cedar (Calocedrus decurrens) U26/U30 and Cappadocian Maple (Acer cappadocicum) V097, allowing those who missed last year’s visit to take a quick look at these interesting trees.

Towards the north of the site, not far from the huge Catherine Parr Oak (a Quercus robur), a collection of oaks allowed easy side-by-side comparison of the different species. These included Lebanon Oak (Quercus libani) H52, Algerian Oak (Quercus canariensis) (probably H25) and Aleppo Oak (Quercus infectoria) (probably H112). In Asia, this latter species often has large galls that have been traditionally used in the tanning and pharmaceutical industries. Turning over some leaves, we did however find some different (tiny) galls: silk button spangle galls. Some of us used a hand lens to view the beautiful embroidery-like structure of these galls.

A collection of different ash species included Red Ash (Fraxinus pennsylvanica) F92, White Ash (Fraxinus americana) F48 and Pumpkin Ash (Fraxinus profunda) F55 & F82. The name Pumpkin Ash refers to the swollen trunk bases which this tree often produces in wet habitats in it’s native range of eastern North America. Graham said it’s possible that the Pumpkin Ash at Thorp Perrow may develop a swollen base over time, but thinks it may not be wet enough.

After lunch, we turned into an area with several species of hawthorn. Graham informed us that the genus Crataegus only dates back to the Eocene but a land bridge once existed between Europe and North America which allowed the migration of species. The fruits of Harbison's Hawthorn (Crataegus harbisonii) C509, which had attractive red sepals, are larger than those of our native hawthorn C. monogyna. It is native to North America where it is now rare in the wild.

In the same planting area as the hawthorns were a number of Strawberry Dogwood (Cornus kousa) e.g. C532. This species is native to East Asia. The trees had abundant edible fruits, resembling ‘crispy strawberries’, which some members sampled.

Looking at it’s best in terms of ripe fruits, was a Guelder-rose (Viburnum opulus), the bunches of shiny red berries standing out from a distance. Also here were two Sorbus species native to the UK which I don’t often see, the Service-tree and the Wild Service-tree:

Service-tree (Sorbus domestica) - the leaflets are more coarsely toothed than in the similar looking Rowan (Sorbus aucuparia). There is uncertainty about the native status of this species in the British Isles but it is thought to be native at some sites such as coastal cliff ledges and rocky woodlands along the Severn Estuary. Clive Stace’s book New Flora of the British Isles (2019) classes it as probably native and rare (RRR status). The species is also planted, and self-sown saplings are sometimes seen on waste ground in urban areas.

Wild Service-tree (Sorbus torminalis) D2 - in the wild it is found in woods, scrub and hedgerows mostly on clay or limestone. Although it is fairly widely planted, it is often regarded as an indicator of ancient woodland, due to the fact that, in our climate, the tree spreads almost exclusively by suckers. The brown berries, known as chequers, can be eaten once they have been allowed to over-ripen or ‘blet’, turning then soft and sweet. Pubs named the ‘Chequers Inn’ may be linked to the use of the berries to flavour beer or a spirit.

Making our way slowly back in the direction of the car park, we paused to look at many species, including the impressive Caucasian Wingnut (Pterocarya fraxinifolia), which Graham said was one of his favourite trees at this time of year. Although we saw this tree last year, we couldn’t resist going back to see it again to admire the distinctive pendent fruits, hanging down like festive decorations.

Also worthy of a mention are the Chinese Hazel (Corylus chinensis) A46 and Turkish Hazel (Corylus colurna) A44. On the ground below the Turkish Hazel, and evident in the canopy above us, were amazing looking round clusters of nuts, each cluster the size of a fist.

Another surprise was Campbell's Magnolia (Magnolia campbellii) BP69. The large knobbly pink fruits were very alien looking. Opening a fallen fruit, we discovered orange seeds inside, reminding us of the colour combination in fruits of our native Spindle (Euonymus europaeus). Graham, after checking with the group “Can you cope with a bit more biology?” gave an interesting summary of the evolution of woody plants and how modern genetic studies have changed how some plants are classified. On a recent visit to Kew, Graham saw a useful diagram which depicts an updated view of the evolution of plant groups. Interestingly, magnolia sits in a group of its own, evolving after ferns and gymnosperms, but before the monocots and dicots.

Before we left, we stopped to admire some huge conifers including Spanish Fir (Abies pinsapo) MP013, Noble Fir (Abies procera) MP011 and Caucasian Fir (Abies nordmanniana) MP056. Although Stace’s New Flora of the British Isles says Caucasian Fir grows to 48m, an online search suggests that some specimens in the Caucasus are 85m tall, which, if correct, would make them the tallest native tree in Europe. Graham informed us that Caucasian Fir is increasingly being used as ‘Christmas trees’ as the leaves are not readily shed indoors.

We ended our day with a trip to Thorp Perrow’s cafe, timing our return to catch the cafe before it closed, and thanked Graham for a thoroughly interesting day. Whilst plant hunting today, we couldn’t help but be distracted by some of the fungi we saw. Andy has kindly provided the below species list of fungi we happened to spot:

Beefsteak Fungus (Fistulina hepatica)

Dryad’s Saddle (Cerioporus squamosus)

False Artist’s Bracket (Ganoderma adspersum)

Little Wheel (Marasmius rotula)

Peeling Oysterling (Crepidotus mollis)

Text by Susan

Photographs by Tom & Susan