Submitted by gsparrow on Mon, 06/22/2020 - 10:57
Ger van den Beuken

DIONYSIA IS A genus containing 50-plus species of perennial plants from the primrose family (Primulaceae), closely related to the genus Primula and native to southwest Asia, particularly in Afghanistan, southeast Turkey, and Iran. Two different mountain ranges are important for dionysias in Iran. The Elburz in the north and the Zagros Mountains running from northwest to southeast. The Zagros range, in particular, has a diversity of locations with different species. Iran is a huge country and to visit all those interesting locations you need to travel more than 1,200 miles (2000 km). The main roads are of good quality but getting into the mountains you definitely need a four-wheel drive car.

Dionysias mainly grow on vertical or curved limestone rocks, almost always protected from rain or snow. However, there are exceptions. Michael Mauser and Brigitte Fiebig from the botanical garden in Tübingen, Germany, were exploring the mountains in 2015 with a small group. In his account, he wrote about the habitat of a new species, D. robusta. This species was not only growing in vertical crevices but also on horizontal places. When they visited this spot it was raining and the plants were completely overwatered and wet. This is a complete surprise, as it means there are still questions about how much wet these plants can endure in nature. This reminds me of a visit to a private garden with a good dionysia collection in the United Kingdom many years ago. It was a very warm summer day and the owner was watering his plants all over with a sprinkler hose. The plants were looking perfect and healthy. I have never risked watering my plants so liberally.
Alpine House Design
In general, dionysias are difficult plants to grow, but there are some exceptions like D. aretioides and D. involucrata. It is important to provide these plants with the right conditions and an alpine house is indispensable to keep these gems going through the year.
My alpine house is about 23 feet (7 m) in length and nine feet (2.7 m) wide, built from stainless steel, hard plastic, and acrylic glass. Six big roof windows, louvers all around, together with two additional vents provide the plants with sufficient air movement. The most important detail is the use of acrylic glass. This material lets more light through than normal glass and is essential for the plants. Many people make the mistake of using polycarbonate. This is much cheaper initially but pretty expensive in the long run as this material turns yellow after a few years. That means a lack of good light and problems with the plants.
The beds in my alpine house are about a foot (30 cm) deep and are level with the ground, so you enter the alpine house by going down a few steps. In this way, I can keep the raised beds cooler during summer. The beds are made waterproof with a thick plastic film and have an irrigation system on the bottom. Over this is a two-inch (5 cm) layer of coarse pebble covered with a water-permeable film. Over that, the beds are filled up with a ten-inch (25 cm) layer of good quality coarse sand. The coarse sand absorbs the water. This is the most important part concerning water management as all my plants are grown in clay pots and sunk into the moist sand. In the front and end of the beds are four-inch (10 cm) wide vertical tubes to check the water level in the beds.

Cultivation and propagation
All my plants are grown in clay pots in a soil-free mineral substrate without any fertilizer. My substrate is a mix of perlite, coarse sand, pumice, seramis (fired clay granules), grit, and a small amount of tufa grit.
This mix provides the plants with a fantastic root system which is essential for a lifespan of at least four or five years. The young plants are potted in four- to eight-inch (10- to 20-cm) pots depending on the species. D. aretioides, for instance, is a fast grower and fills up an eight-inch (20-cm) pot in a few years. Many other species are slow, compact growers and are satisfied with a four-inch (10-cm) pot for the first four to five years. It is highly recommended to read about the different species. You will need to repot the plants every four to five years to provide them with fresh substrate. This is not a job without risk as older plants become potbound. The only acceptable method is to sink the pots in water until they have absorbed the water. Do not try to get the plants out of the pot but destroy the pot with a hammer or other tool. In this way, the root system remains intact. Repot and water the plant. Watering should always be done along the rim of the pot to avoid any wetness on the plant. If necessary, I give the plants a spray against fungus. I never fertilize the plants. This is the best way to keep your plants compact. During warm periods with bright sun, you need to shade the plants.
Propagation is possible from seeds or cuttings. To get seeds, however, you need the right pollinator or you need to be a pollinator yourself. We do not have the right bumblebee in my garden, therefore I propagate all the plants from cuttings. For this work, you must be precise and patient. The best time is right after blooming when growth is active. I stick my cuttings in very fine pumice and put them away from direct sunlight. Check the cuttings every few days and set the container in water to absorb moisture if necessary. Depending on the species you will have to be satisfied with a maximum of a 50% success rate. I pot the newly rooted plants in small, two-inch (5-cm) clay pots and let them grow for another year.

The Plants
Dionysias are perennial, herbaceous plants forming a woody base. They grow into dense or loose cushions or dwarf shrubs. The leaves are usually in terminal rosettes.
In early spring, during mild winters sometimes starting in January, yellow, purple, violet, or pink flowers bloom. The flowers can be borne in an inflorescence with several whorls or in a simple umbel, but most are solitary, borne directly on the leaf-rosette. The calyx and corolla are usually fused at the bottom into a long flower tube. The flowers can be either thrum- or pin-eyed.
D. afghanica GW/H1308 is one of the most beautiful and impressive species. The original plant, collected as three cuttings by Christopher Grey-Wilson and Tom Hewer in Afghanistan, is rare in cultivation. The plant grows mainly in the Darrah Zang Range at 4,600 feet (1,400 m) on steep limestone cliffs. The plants form sticky grey-green cushions. The flowers are solitary and sessile, the corollas pale to mid-violet with a darker throat. Michael Kammerlander has introduced a wonderful number of hybrids of this species with dark or pale purple, white, and even yellow flowers. Most spectacular are D. ‘Zdeněk Zvolánek’, ‘Mike Bramley’, and ‘Perlmut’.
D. archibaldii forms greyish, rather lax cushions, up to 12 inches (30 cm) across. Flowers are solitary and sessile; the corolla is pale pinkish-violet to purple. This species is only known from the area between the Koohrang and Bazoft valleys in Bakhtiari Province, Western Iran, on shaded and semi-shaded limestone cliffs, at 7,380 to 14,100 feet (2,250-4,300 m). There are numerous hybrids of this species in cultivation.
D. aretioides from Elburz Mountain in north Iran grows on shady limestone rocks up to 9800 feet (3000 m). It forms lax to fairly dense cushions up to 20 inches (50 cm) wide in the wild and over 15 inches (40 cm) in cultivation. The sessile, yellow flowers are solitary or occasionally produced two per rosette. Several forms are in cultivation like ‘Gravetye’, ‘Paul Furse’, and ‘Phyllis Carter’. The most spectacular is ‘Bevere’, a selected form by Ron Beeston with big deep-yellow flowers.
D. bryoides is relatively widespread in Iran, on the Zagros Mountains in Fars and Esfahan provinces, growing on sunny or shaded limestone cliffs at 5,900 to 9,200 feet (1,800 - 2,800 m). The flowers are pale to deep pink and violet, with a white center. Several different forms have been introduced from different expeditions. ‘Eric Watson’, ‘Henrik Zetterlund’, and ‘Bolero’ are the most impressive.
D. curviflora comes from central Iran, Yazd province, Shir Kuh and Kuh-e Barfkhane growing on shaded or partially shaded basalt or volcanic cliffs at 8,200 to 13,100 feet (2,500 – 4,000 m). It forms dense cushions with pink to lilac solitary, sessile flowers. This is one of the easiest species to grow. The form JCA 2800 is, for me, the best one. There are numerous hybrids in cultivation.
D. esfandiarii grows in Kuh-e Kataban near Abadeh in Fars province, western Iran, at 8,500 feet (2,600 m). It forms dense grey-green cushions. The flowers are sessile and solitary with a violet corolla about a third of an inch (8-9 mm) in diameter. It can be shy-flowering in cultivation. Propagation from cuttings is difficult, often succumbing to rot before rooting.
D. freitagii comes from shaded limestone cliffs in northern Afghanistan at an elevation of 6,300 feet (1,900 m). This is one of the most beautiful and extremely floriferous species and is relatively easy to cultivate. It forms dense, deep-green, rather sticky, cushions, up to six inches (15 cm) in diameter in cultivation, occasionally larger. Flowers are solitary, sessile, with a violet to violet-purple corolla with a darker zone surrounding a white eye. It is a rare species because of the poor rooting results from cuttings.
D. gaubae is a species forming rather lax cushions up to ten inches (25 cm) in diameter. The bright yellow flowers are sessile. It is endemic in Khorramabad in Lorestan province, Iran, growing on steep limestone cliffs between 3,300 and 7,874 feet (1,000 – 2,400 m).
D. haussknechtii forms dense, farinose cushions. The yellow flowers are solitary and sessile. Plants in cultivation come from several collections, all from 7,410 to 8,200 feet (2,260 – 2,500 m) on Ghadee Kuh near Shoul Abad, Lorestan province, western Iran.
D. involucrata is a species from the Pamir range in Pakistan growing on shaded cliffs at about 6,560 feet (2,000 m). It forms rather dense, deep-green cushions, up to 12 inches (30 cm) in diameter in cultivation. It flowers on a stalked umbel with bracts like the leaves, but larger and often lobed. The corolla is violet or violet-purple with a white eye. There is even a white form in cultivation. This is the only species I can propagate from seeds.
D. iransharii forming dense, very hairy cushions which are usually greyish-green although some clones are bright and almost green. The flowers have a violet corolla, 0.2 inches (5-6 mm) in diameter on a 0.43 inch (11 mm) tube. This is absolutely one of my favorite species. It was first discovered in 1974 by M. Iranshahr but only introduced into cultivation in 1998. All collections in cultivation are from Kuh-e Pashmaku in Bakhtiari province, Iran where it grows between 8,200 and 10,200 feet (2,500 – 3,100 m) on limestone cliffs. It is one of the more difficult species to cultivate.
D. khatamii forms open cushions of small rosettes to 0.4 inches (10 mm) in diameter, but usually less. This species is related to D. curviflora, and like it, grows on igneous rocks as well as limestone. It was discovered in Iran in 2002, in Darreh Damghan south of Mehriz, Yazd province, Iran, at 8,200 to 8,900 feet (2,500-2,700 m). The corolla is violet, occasionally pinkish, and 0.2 to 0.3 inches (5-8 mm) in diameter. This is one of the more susceptible species to botrytis.
D. khuzestanica is found on the border of Bakhtiari and Khuzestan provinces in western Iran. It forms dense green cushions with sessile, yellow flowers. It is closely related to D. zagrica.
D. lamingtonii forms small, slow-growing, neat, grey-green cushions. The flowers are solitary and sessile with a yellow corolla on a tube 0.4 to 0.55 inches (10-14 mm) long. This is one of the finest species from western Iran, found in various locations in Bakhtiari province, on sunny or partially shaded limestone cliffs, at 5,600 to 9,700 feet (1,700-2,950 m). The cushions are prone to botrytis and can die rapidly and without warning. They can look very dead during the winter, but may well be still alive, so it is prudent to wait until spring before discarding.
D. microphylla GW/H 1302. This clone forms hard, very neat, grey-green cushions, up to 8 inches (20 cm) in diameter in cultivation. The flowers are solitary or up to four in an umbel, occasionally with an extra whorl above. The bracts are small, similar to the leaves. The corolla is pale to deep violet. This species is endemic to northwestern Afghanistan, Maymana province, near Belcheragh in the Darrah Zang gorge, on sunny or semi-shaded slopes or vertical limestone rocks, at 3,900 to 4,600 feet (1,200-1,400 m). This is one of the most desirable species, but extremely slow-growing and very difficult to propagate.
D. robusta. This is a relatively recently discovered species, found in 2015 in the unexplored Ilam province in western Iran, specifically in the Dinar-Kuh region, southwest of Abdanan at the relatively low elevation of 5,640 feet (1,720 m). It forms large, bluish, grey-green cushions up to 27 inches (70 cm) in diameter in the wild. The flowers are yellow, with the corolla lobes only slightly overlapping. This species is still new for me but the first rooting results from cuttings are promising.
D. sarvestanica forms dense, caespitose grey-green cushions up to 6.7 inches (17 cm) in diameter in cultivation. The flowers are solitary and sessile with bright-yellow, 0.2- to 0.3-inch (6-8 mm) corollas on tubes 0.3 to 0.4 inches (8-10 mm) long. It comes from Shiraz and Fars provinces in Iran.
D. tapetodes is widely distributed from Turkmenistan and north-eastern Iran, throughout the mountains of Afghanistan to the border of Pakistan, on shaded or semi-shaded limestone cliffs and outcrops at 3,300 to 10,500 feet (1,000-3,200 m). It forms large cushions, up to 14 inches (36 cm) in diameter in cultivation.  The yellow flowers are solitary and sessile. The species is considered one of the easiest to cultivate and most forms are very floriferous. Cuttings are also relatively easy to root.
D. viscidula has been only found once in northwestern Afghanistan, Maymana province, near Belcheragh, on shaded or semi-shaded limestone cliffs in the Darrah Zang gorge at 4,600 feet (1,400 m). It is still very rare in cultivation, and far more difficult than its closest ally D. freitagii. It forms cushions 12 inches (30 cm) in diameter once established. The flowers are pale violet-pink, without a darker zone but with a clear white eye, and 0.27 to 0.4 inches (7-10 mm) in diameter.
D. zetterlundii forms dense, farinose cushions. The flowers are yellow and 0.4 inches (10 mm) in diameter. Plants in cultivation were introduced from limestone cliffs at 8,860 to 9,200 feet (2,700-2,800 m) on the Charee Pass between the Kuhrang and Bazoft Valleys in Bakhtiari province, Iran.
This list of species is by no means complete, but they are the species that I have experience propagating and cultivating in my collection. D. crista-gallii, D. iranica, D. janthina, D. michauxii, and D. tacamahaca are some of the species new in the collection.
A number of selected forms or hybrids are also definitely worth adding to any dionysia collection. A few of the most attractive include D. ‘Bolero’, D. ‘Maria’, D.’Eric Watson’, D. ‘Göteborg’, D ‘Lycaena’, D. ‘Yellow Stone’, D. ‘Monika’, D. ‘Annielle’, and D. ‘Butterfly’.