Origin and Habitat: Rio Ocoña to Camana, Southern Coast of Arequipa, Peru.
Altitude: 20-300 metres above sea level.
Habitat: Grows together with Haageocereus decumbensSN|5625]]SN|5625]] in very dry desert areas where it almost never rains and where only the occasional sea fog drift inland.

• Islaya brevicylindrica Rauh & Backeb.
• Neoporteria islayensis f. brevicylindrica (Rauh & Backeb.) Donald & G.D.Rowley

• Eriosyce islayensis (C.F.Först.) Katt.
• Echinocactus islayensis C.F.Först.
• Islaya islayensis (C.F.Först.) Backeb.
• Malacocarpus islayensis (C.F.Först.) Britton & Rose
• Neoporteria islayensis (C.F.Först.) Donald & G.D.Rowley
• Parodia islayensis (C.F.Först.) Borg
• Eriosyce islayensis subs. grandis (Rauh & Backeb.) G.J.Charles
• Islaya grandis Rauh & Backeb. in Backeb.
• Islaya islayensis subs. grandis (Rauh & Backeb.) G.J.Charles
• Neoporteria islayensis var. grandis (Rauh & Backeb.) Donald & G.D.Rowley
• Eriosyce islayensis subs. omasensis (Ostolaza & Mischler) G.J.Charles
• Eriosyce omasensis (Ostolaza & Mischler) Ostolaza
• Islaya omasensis Ostolaza & Mischler
• Neoporteria omasensis (Ostolaza & Mischler) Ferryman
• Islaya bicolor Akers & Buining
• Neoporteria bicolor (Akers & Buining) Donald & G.D.Rowley
• Islaya brevicylindrica Rauh & Backeb.
• Neoporteria islayensis f. brevicylindrica (Rauh & Backeb.) Donald & G.D.Rowley
• Islaya copiapoides Rauh & Backeb.
• Neoporteria islayensis var. copiapoides (Rauh & Backeb.) Donald & G.D.Rowley
• Islaya copiapoides var. chalaensis F.Ritter
• Islaya chalaensis F.Ritter
• Islaya copiapoides var. pseudomollendensis F.Ritter
• Islaya divaricatiflora F.Ritter
• Neoporteria islayensis var. divaricatiflora (F.Ritter) Donald & G.D.Rowley
• Islaya flavida F.Ritter
• Islaya grandiflorens Rauh & Backeb.
• Neoporteria islayensis f. grandiflorens (Rauh & Backeb.) Donald & G.D.Rowley
• Islaya grandiflorens var. spinosior Rauh & Backeb.
• Neoporteria islayensis f. spinosior (Rauh & Backeb.) Donald & G.D.Rowley
• Islaya grandiflorens var. tenuispina Rauh & Backeb.
• Islaya grandis var. brevispina Rauh & Backeb.
• Islaya grandis var. neglecta A.Simo
• Islaya islayensis var. minor (Backeb.) F.Ritter
• Islaya minor Backeb.
• Neoporteria islayensis f. minor (Backeb.) Donald & G.D.Rowley
• Islaya krainziana F.Ritter
• Neoporteria krainziana (F.Ritter) Donald & G.D.Rowley
• Islaya longicarpa Kníže
• Islaya maritima F.Ritter
• Islaya minuscula F.Ritter
• Islaya molendensis (Vaupel) Backeb.
• Echinocactus molendensis Vaupel
• Neoporteria islayensis f. molendensis (Vaupel) Donald & G.D.Rowley
• Islaya paucispina Rauh & Backeb.
• Islaya paucispina var. curvispina Rauh & Backeb.
• Neoporteria lindleyi f. curvispina (Rauh & Backeb.) Donald & G.D.Rowley
• Islaya paucispinosa Rauh & Backeb.
• Islaya solitaria n.n.
• Islaya unguispina F.Ritter
• Neoporteria lindleyi C.F.Först.
• Echinocactus lindleyi C.F.Först.

• Eriosyce islayensis cv. TAIWAN
• Islaya cv. TAIWAN

Description: Eriosyce islayensisSN|1713]]SN|1713]], formerly known as Islaya islayensisSN|14243]]SN|1716]], is a small cactus with very woolly areoles end dark spreading spines, it is indeed very variable and has received many names, but it is clear from fieldworks that the different wild populations constitute a single but multiform species. Islaya brevicylindricaSN|14243]]SN|14243]] has shorter grey green cylindrical stems, but similar short cylindrical individuals can be found in other populations too, and also two plants of the same population can look very different. Islaya brevicylindricaSN|1716]]SN|14243]], is generally included within (as a synonym of) Eriosyce islayensisSN|1713]]SN|1713]], suggesting that there is not really a fundamental difference between the two.
Stems: Initially globular, but slightly elongated to shortly cylindrical with age, grey-green, 5 to15 cm tall (rarely up to 70 cm tall), 5-10(-20) cm in diameter. Apex densely woolly.
Ribs: 19-22 low and obtuse and more or less tuberculate.
Areoles: Approximate, large, conspicuously woolly, with creamy-white to grey-brown felt.
Roots: Fibrous.
Spines: Variable in size and in colour whitish with reddish tips, changing to grey with age.
Central spines: 1-3 spreading and markedly directed downward, thick, about 20 mm long.
Radial spines: About 20, shorter, radiating, 7-10 mm long, but sometimes less than 3 mm long.
Flowers: Diurnal, wide funnelform, yellow 1,5-2,5 cm long and in diameter (up to 4 cm in the variant known as grandiflora), born on younger areoles from a yellowish woolly crown in summer. Pericarpel and floral tube short scaly. Scales with tufts of dense wool and long reddish bristles. Petals yellow, sepaloids often orange or reddish. Style yellow.
Fruits: Characteristic, up to 5 cm long, club shaped, balloon-like, pinkish to red, when mature inflated, openings by basal pores. Pericarp initially fleshy but the interior always dry when mature.
Seeds: Broadly oval.

Notes: Eriosyce islayensisSN|1713]]SN|1713]] has a large area of distribution and is a very variable species. The difference between populations is the frequency of the appearance in which these forms do occur. So it is possible that two individuals of two different populations can look very similar and also, that two plants of the same population can look very different. However when you are looking at the whole population, you can see the difference between one population and another.

Bibliography: Major references and further lectures
1) Fred Kattermann "Eriosyce (Cactaceae): The Genus Revised and Amplified" David Hunt, 1994
2) Edward Anderson “The Cactus family” Timber Press, Incorporated, 2001
3) James Cullen, Sabina G. Knees, H. Suzanne Cubey "The European Garden Flora Flowering Plants: A Manual for the Identification of Plants Cultivated in Europe, Both Out-of-Doors and Under Glass" Cambridge University Press, 11/Aug/2011
4) David R Hunt; Nigel P Taylor; Graham Charles; International Cactaceae Systematics Group. "The New Cactus Lexicon" dh books, 2006
5) Edgar Lamb, Brian Lamb “The Illustrated Reference on Cacti & Other Succulents” Volume 5 Blandford Press, 1978
6) Jan ?íha “Illustrated Encyclopedia of Cacti and Other Succulents” Book Sales, Incorporated, 01/set/1993
7) Curt Backeberg “Die Cactaceae: Handbuch der Kakteenkunde.” 2. ed.. Volume 2, Gustav Fischer Verlag, Stuttgart New York 1983
8) Dillon, M.O. "Lomas Formations - Peru" pp. 519-527. In: S. D Davis, V. H. Heywood, O. Herrera-McBryde, J. Villa-Lobos and A. C. Hamilton (eds.), Centres of Plant Diversity, A Guide and Strategy for their Conservation. WWF, Information Press, Oxford, U.K. 1997
9) Walther Haage “Kakteen von A bis Z” 3. ed. Quelle & Meyer Verlag, Heidelberg 1986
10) N. L. Britton, J. N. Rose: “The Cactaceae. Descriptions and Illustrations of Plants of the Cactus Family.” Volume III, The Carnegie Institution of Washington, Washington 1922
11) E Haustein “Der Kosmos Kakteenfuehrer (the Kosmos Cactus Guide)” United States, Balogh Scientific Books 01/Dec/1998
12) Dr Michael O. Dillon “Lomas formations, Peru” (Field Museum of Natural History, Center for Evolutionary and Environmental Biology, Department of Botany, Chicago, IL 60605- 2496, U.S.A.). http://botany.si.edu/projects/cpd/sa/sa42.htm

Cultivation and Propagation: It is an extremely xerophytic, summer-growing, species adapted to very dry soils that, like many cacti of the Peruvian deserts, present some problems in cultivation. It is in fact somewhat rot prone if kept in a non ventilated place.
Growth rate: Slow-growing.
Soil: It requires a very fast draining drying open mineral, sandy-gritty cactus composts. Provide a very good drainage.
Exposure: It is suited for sunny-brightly exposure, but can tolerate light shade. However it will do its best only with lots of sun and become stressed with inadequate light which could result in poor growth and unnatural shape. It has a good heat tolerance.
Watering: Water regularly in summer, but do not over-water and keep it completely dry during winter. Mature individuals easily rot and die especially after transplanting so be extremely cautious with watering. Keep dry in winter or when night temperatures remain below 10° C. Water it less than average if in bigger pots.
Fertilization: Feed them once during the growing season with a fertilizer specifically formulated for cactus and succulents (high potash fertilizer with a dilute low nitrogen), including all micro nutrients and trace elements diluted to ½ the strength recommended on the label. They thrive in poor soils and need a limited supplies of fertilizer to avoid the plants developing excess vegetation, which is easily attacked by fungal diseases.
Special need: It is suited for airy exposures. Provide very good ventilation. Nearly all problems occur as a result of overwatering and poor ventilation, especially when weather conditions are dull and cool or very humid. They must have very dry atmosphere.
Hardiness: It likes warmth (recommended minimum winter temperature 5° C), but hardy to at least -5°C (it can probably tolerate freezing temperatures down to -10° C for brief periods) It has a good heat tolerance.
Pests & diseases: These cacti may be attractive to a variety of insects, but plants in good condition should be nearly pest-free, particularly if they are grown in a mineral potting-mix, with good exposure and ventilation. Nonetheless, there are several pests to watch for.
- Red spiders: Red spiders may be effectively rubbed up by misting the plants from above.
- Mealy bugs: Mealy bugs occasionally develop aerial into the new leaves and flowers with disfiguring results, but the worst types develop underground on the roots and are invisible except by their effects.
- Scales, thrips and aphids: These insects are rarely a problem.
- Rot: Rot is only a minor problem if the plants are watered and “aired” correctly. If they are not, fungicides won't help all that much.
Propagation: Usually propagated from seeds (seldom produces offsets) or graft. The seeds can be sown in pots of fine, well-drained sandy soil, any time during the spring when temperatures are warm. Cover the seeds with a fine layer of grit and water from below with a fungicide to prevent damping off. For the 1-2 weeks cover the pots with a sheet of glass/clear perspex to keep the humidity levels high. Remove the glass and replace it with light shade-cloth and mist once or twice a day for the next two weeks after which most seeds should have germinated. From then on mistings can be reduced to every second and then every third day as the little plants grow. The seedlings should not be disturbed until they are well rooted after which they can be planted separately in small pots. Sometimes it is grafted onto a strong grafting stock like Selenicereus sp. to avoid root rot problems as plants grafted on an hardy stock are easy to grow and no special skill is required. Such grafted seedlings can be been successfully cultivated for years. Mature plants imported from the native habitats usually did not take roots and dyes in a few months.