Mediterranean Garden Society

A Garden on the Karst

by Duncan J.D. Smith
photos by Duncan J. D. Smith and Tina Klanjšcek / Coop. Rogos

Photographs to illustrate the article published in The Mediterranean Garden No. 115, January 2024

The photo at the top of this page shows Smilax growing on the Coastal Cliffs of the Giardino Botanico Carsiana, Trieste (Photo Tina Klanjšcek / Coop. Rogos)

Duncan Smith is a writer of travel guides, and this year he explored the north-east Italian city of Trieste, that “half real, half imagined seaport” on the Adriatic, as author Jan Morris so eloquently described it. He writes:

The most notable garden is the Municipal Botanical Garden of Trieste (Civico Orto Botanico di Trieste). There is another garden in Trieste, however, that is less well known but no less important. The Botanical Garden of the Karst (Giardino Botanico Carsiana) can be found high above the city on the limestone plateau that provides Trieste with its dramatic backdrop. Known as the Karst, this rugged upland is famously riddled with sinkholes and caves that spirit away both rivers and rainfall from the permeable surface. Combined with its shady pine-clad slopes and scrubby upland, the Karst might at first appear botanically uninteresting. It is, however, home to some 1,600 plant species and serious botanists will walk miles in search of them. Fortunately for the layperson, around six hundred species can be easily enjoyed by visiting garden.

Winding paths in the Giardino Botanico Carsiana (Photo Duncan J. D. Smith)

Located outside the village of Sgonico, the Botanical Garden of the Karst was established in 1964 by a group of local botanists, including a local pharmacist, Gianfranco Giotti, who purchased the site; it has been administered since 2016 by the Autonomous Region of Friuli Venezia Giulia. The founders selected a piece of land for the garden that contained a collapsed sinkhole known as a doline, meaning ‘little valley’ in the Slovenian spoken by most natives of the Karst, a funnel-shaped feature typical of the Karst, created by the dissolution of the limestone through the action of naturally acidic rainfall. The site conveniently incorporated almost all of the Karst’s nine key geomorphologic formations, each of which hosted its own specific flora. In this way a botanical synthesis of the Karst, which in reality covers 175 square miles along the Italian-Slovenian border, could be presented within the relatively tiny confines of the 1.2-acre garden. Most of the garden’s vegetation therefore grows spontaneously according to habitat, with the majority of species already present when the garden was created and only very few imported.

By following the garden’s winding footpaths in a clockwise direction, the nine habitats are encountered in the following order:

Karstic scrub - Tyrol Knapweed (Centaurea nigrescens) (Photo Duncan J. D. Smith)

First is the karstic scrub, the most common environment on the Karst, which rapidly became established with the cessation of grazing after the Second World War. The rocky, fissured substructure overlain by thin soil supports scattered hop hornbeam (Ostrya carpinifolia), flowering ash (Fraxinus ornus), and downy oak (Quercus pubescens), interspersed with shrubby cherries and smoke bush (Cotinus coggygria), as well as clumps of autumn moor grass (Sesleria autumnalis), wild peony (Paeonia officinalis), Istrian hellebore (Helleborus istriacus), white dittany (Dictamnus albus), and deep pink summer-blooming cyclamen (Cyclamen purpurascens). The latter, together with Tyrol knapweed (Centaurea nigrescens) and the toxic so-called autumn crocus (Colchicum autumnale), typifies the garden’s purple-hued blooms of late summer and autumn, in contrast to its mainly yellow (and more prolific) blooms of spring and early summer.

Karstic scree (Photo Tina Klanjšcek / Coop. Rogos)

Second is the karstic scree, which comprises steep and unstable limestone rubble, sun-drenched with little water or nutrients. This is one of only two habitats in the garden that had to be created artificially. Plants here are few and are limited to prostrate herbaceous perennials with deep roots and narrow leaves to minimise transpiration. They include shining bedstraw (Galium lucidum), buckler-mustard (Biscutella laevigata), the tall conical spikes of the chimney bellflower (Campanula pyramidalis) and clumps of fescue grass (Festuca spectabilis). The scree also hosts common houseleeks (Sempervivum tectorum) and the endangered endemic Illyrian broom (Genista holopetala).

Third comes the karstic woodland, which represents the very few remaining fragments of the area’s ancient oak forest, lost to centuries of deforestation. The canopy is formed by deciduous sessile oak (Quercus petraea), with a field layer dominated by autumn moor grass.

Dry grassland (Photo Tina Klanjšcek / Coop. Rogos)

Next is the dry grassland, which represents deforested areas grazed by sheep and goats since the arrival of Bronze Age pastoralists some five thousand years ago. Plants resistant to grazing and tolerant of aridity include yellow rock knapweed (Centaurea rupestris) - the garden’s emblem - and dwarf sedge (Carex humilis), alongside endemic species such as the spring-flowering gentian (Gentiana verna) and Potentilla tommasiniana. Blossoms between March and August arrive courtesy of the Triestine gentian (Gentiana verna subsp. tergestina), Illyrian iris (Iris pallida subsp. illyrica), mountain pasque (Pulsatilla montana) and crested knapweed (Centaurea cristata).

Coastal cliffs (Photo Tina Klanjšcek / Coop. Rogos)

Quite different is the area representing the coastal cliffs at the edge of the Karst. In the garden it is represented by a south-facing slope planted with sclerophyllous Mediterranean evergreens such as holm oak (Quercus ilex), bay (Laurus nobilis), mock privet (Phillyrea latifolia), Viburnum tinus and the rambling Etruscan honeysuckle (Lonicera etrusca).

Coastal cliffs another view (Photo Tina Klanjšcek / Coop. Rogos)

There are also aromatic and spiny species such as common sage (Salvia officinalis), myrtle (Myrtus communis), the resinous turpentine tree (Pistacia terebinthus), Jerusalem thorn (Paliurus spina-christi) and wild asparagus (Asparagus acutifolius).

Doline woodland - Cyclamen purpurescens (Photo Duncan J. D. Smith)

Next comes the doline woodland. The doline, which tapers from 860 feet across at the rim down to 131 feet at the base, gets cooler the deeper it goes. The flora reflects this with trees normally found at higher altitudes, such as common hornbeam (Carpinus betulus), hazel (Corylus avellana) and the small-leaved lime (Tilia cordata). In between grows the dainty Isopyrum thalictroides, European wild ginger (Asarum europaeum), wood anemone (Anemonoides nemorosa), dogstooth violet (Erythronium dens-canis), spring vetchling (Lathyrus vernus) and the blue alpine squill (Oziroe biflora syn. Scilla bifolia).

Upland karst - alpinetum (Photo Tina Klanjšcek / Coop. Rogos)

The upland karst area also benefits from a cooler climate, as well as greater rainfall. This is replicated in the garden using a series of pools and channels to cool the soil, which in turn supports the growth of hairy alpenrose (Rhododendron hirsutum), dwarf alpenrose (Rhodothamnus chamaecistus), mountain avens (Dryas octopetala), purple-pink Carniolan primrose (Primula carniolica) and henbane bell (Scopolia carniolica).

Ponds (Photo Tina Klanjšcek / Coop. Rogos)

The ponds of the Karst are few and far between, being man-made clay-lined pools created artificially by villagers for use by themselves and their livestock. They provide the Karst’s only aquatic habitats, typified by rushes on the banks, yellow flag (Iris pseudacorus) and fen ragwort (Senecio paludosus) at the margins, and white (Nymphaea alba) and yellow (Nuphar lutea) water-lilies in the deeper water.

Karstic pothole (Photo Duncan J. D. Smith)

The garden ends with the ominous-sounding karstic pothole. This vertical shaft, known locally as a foiba (or fojba), is located at the bottom of the doline and is accessed by means of a narrow 20-foot-wide entrance. It then plunges to a depth of almost 130 feet and receives little light. Accordingly, its walls support little vegetation, with just a few hart’s-tongue ferns (Asplenium scolopendrium syn. Phyllitis scolopendrium) and then, deeper down, only moss (Thamnobryum alopecurum). The deepest, darkest recesses of the foiba host nothing more than blue-green algae barely visible in the gloom.

This article could not have been written without the considerable help of Pierpaolo Merluzzi and Paul Tout at the Botanical Garden of the Karst. My thanks go to them both.

The Municipal Botanical Garden of Trieste (Civico Orto Botanico di Trieste) at Via Marchesetti 2

The Botanical Garden of the Karst (Giardino Botanico Carsiana) outside Sgonico

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