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29 Sept 2023

The PLANTS project: three autumn highlights

Written by Nicola Douglas, PLANTS Inventory Officer
Colchicum ‘Waterlily’, photographed at Inverewe in September
Keeping interest going in the garden into autumn is not as hard as it may seem. Niki Douglas picks a range of plants she encountered in Trust gardens which can extend the season.

As the weather starts to change in September, the PLANTS project round up a second year auditing the Trust’s gardens. The North Team (of which I’m a member) have audited 7,845 plants over the last few months at Leith Hall, Castle Fraser, House of Dun, Balmacara and Inverewe. I’ve been left with a deeper understanding of the wide range of plants within the Trust’s collection.

Here are three of my favourite plants that come into their own after summer comes to an end.

Cercidiphyllum japonicum (katsura tree)

I have a distinct love of the ancient Cercidiphyllum genus (commonly know as katsura) with its golden heart-shaped leaves, and while auditing Castle Fraser this early autumn I caught a hint of its caramelly scent on the cooling air. It’s the high sugar and maltol content that produces this sweet odour, reaching its peak in autumn as the leaves float to the ground in hues of yellow, pink and sometimes red. Similar in leaf size and shape to the Cercis tree (redbud), Cercidiphyllum translates as ‘leaves like a Cercis’ – phylla being a Greek word meaning leaf. The two genera can be distinguished by the general arrangement of deciduous leaves: Cercidiphyllum opposite leaves, Cercis alternating ones.

The spring flowers are small and borne before the leaves emerge, sometimes so prolifically that the plant takes on a red hazy look. The genus is dioecious – with separate female and male plants – which tend to have slightly different forms, the former growing more outwardly and wider but both often multi-stemmed.

Fossils dating back 1.8 million years have been found and this prehistoric, long-lived tree has ancient folklore surrounding it in its native habitats of Japan and parts of China. These tales associate the katsura tree with the moon and its shadows. In one fable, a man has been sentenced to continually chop down a giant katsura tree on the moon that eternally regenerates. Indeed, the wood can be coppiced, back here on earth! The wood is used in furniture making and often chosen for the board used in the ancient Chinese game of Go, reportedly the oldest known board game, invented over 4,500 years ago.

Colchicum autumnale (autumn crocus)

The small, delightful vase-like flowers of Colchicums can initially look like crocus, and sometimes are called autumn crocus but are NOT actually true crocuses! While auditing Inverewe this September I was determined to understand more about this species.

Colchicums belong to their own family (and have a larger number of central parts). Crocus sit under the Iris family (have fewer central parts). There are many species and cultivars within the Colchicum family however the presence of the poisonous compound colchine is the determining characteristic of this family. This is a highly toxic compound that disrupts cell division.

Colchicum leaves are quite substantial, emerging several months after flowering has finished and developing throughout spring – it’s July before this luxurious greenery has slowly declined, boosting the below-surface energy reserves in the corm (a short underground plant stem used for storage). Tubers, bulbs and corms are types of geophytes, a word created as part of a plant classification system devised by Danish botanist Christen C. Raunkiær in 1904 with hysteranthous leaves, ie flowering and leaf growth happen in different time periods. Colchicums have a dormancy through the warm summer months after the leaves have withered away, before gorgeous flowers unexpectedly emerge in early autumn, often after a short period of rain. The flowers are ‘unclothed’ by foliage, hence one of the other common names is ‘naked ladies’. After the flowers die back, the plant returns to dormancy again over the depths of winter.

The flower colour ranges through pastel pinks and lilacs to bright pink-purples, often with a white centre. Some species show tessellation, a kind of checkerboard effect within the petals. A double form, Colchicum ‘Waterlily’ is a hybrid cross between Colchicum autumnale and Colchicum speciosum and looks spectacularly luminous in evening light.

Clematis tangutica (golden clematis)

The last audit I completed this year was a seasonal revisit to Crathes Castle. Clematis tangutica, a vigorous and hardy clematis that flowers from late summer onwards, seemed like they were nodding a farewell to the departing high summer sun, the golden yellows of their lantern like flowers smoothing the passage into autumnal temperate weather. The singularly produced flowers extend their appeal towards winter by producing masses of dense ornamental seed heads, each carrying numerous silky, feathery projections that shimmer in the lower sunlight angles and frosty mornings.

One of the common names for the tangutica group is ‘orange peel’ clematis, due its unusually thick tepals. This term comes from a blending of the French words petale and sepale (in the 19th century) giving us a name for a singular structure which both protects the flower in bud (sepals) and provides a colourful whorl when open (petals).

The native range of Clematis tangutica spans central Asia to China. Introduced to some northern parts of Europe and North America, it has dispersed itself widely and there are quite a few differing and related species displaying properties such as scent, vigour or outer colouring of the tepals and flower stems. Clematis tangutica can be found at Crathes Castle and Drum Castle in Aberdeenshire, as well as at Inverewe in Wester Ross.

Autumn is a season where a variety of trees, bulbs and climbers put on a beautiful show. Each of these properties has fantastic walled gardens, where I could happily spend considerable time appreciating the varying details of their immensely diverse plant collections.

Plant Listing at the National Trust for Scotland (PLANTS) is the biggest horticultural audit project undertaken by the Trust and aims to celebrate, protect and better understand the flora and vegetation across our gardens and designed landscapes.

Read more about the PLANTS project

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