Islaya islayensis is native to Chile North and Peru where the plant grows in very dry desert areas or in high rocky cliffs and can spread up to 250 m of altitude.
Islaya islayensis is an uncommon cactus belonging to the Cactaceae botanical family. The plant has a solitary habit, can reach up to 15 cm in height and 10 cm in diameter and forms a long taproot. The stem is spherical, light green to dark green in color, arranged in 15-20 well marked ribs made of prominent tubercles. The areoles are large, very downy, white and woolly and bear the spines. The spines are 5-10 per areola and are long, sharp, spider-like, reddish to shiny black. The number, shape and size of spines vary by populations. Blooming occurs during the Summer and the blossoms are borne at the apex of the stem. Flowering is rare and is possible only in individuals who have reached the maturity. The flowers are small, funnel-shaped, pale yellow and rarely magenta, diurnal. The floral tube has many bristle-like, tipped, brown scales. The fruits are club-shaped to globose, fleshy and red in color.
The plant takes many years to grow into an adult individual but it easy to cultivate. The plant needs a full light sun exposure but prefers partial shade during the summer. Long exposure to direct sun-light can cause burns and burnt spots. The plant does not like temperatures below 5°C so it needs to be placed indoors in the coldest periods. Too low temperatures can cause the stem or leaves to break due to water freezing inside the tissues. Temperatures between 8 and 15 °C allow the plants to enter vegetative rest which is essential for the flowering of the following year. Plants should not be placed inside the house where average temperatures of 20 degrees prevent vegetative rest. For the soil you can use a light and draining soil made of a mix of sand, soil and peat. The pumice should always be placed on the bottom of the pot. Remember to use a perforating pot to drain excess water. Watering can be done regularly during the vegetative period. Irrigation is proportional to the size of the pot, the position and the season. In Spring and Autumn the plant can be watered with a glass of water every 7-10 days; in summer it can be watered every 3-5 days. Decrease the amount of water if the plant is kept indoors or if the pot is smaller than 12 cm. The plant is used to growing in poor soils, for this reason it does not need abundant fertilization, it is sufficient to fertilize once in spring and once in summer. If the pot starts to be too small for the plant you can repot the plant in a pot 2 cm wider. Repotting should be done early in the growing season with fresh new potting soil; when the plant reaches 10 cm in diameter it no more needs it. Choose rather deep pots to easily contain the deep taproot. Be careful to red spiders and mealy bugs.
The plant can be propagated exclusively by seed. By seed it is very simple to propagate the plant, it is enough to sow the seed in a sandy loam and keep it with a high level of humidity and at temperature of 25 C°. To fast the propagation, you can try to immerse the seeds in water for 1 day. Germinating usually occurs in 1-2 weeks.
Islaya is the name of the Peruvian locality where Backeberg, discoverer of the genus, found the first specimens of this cactus.
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