Echinopsis (2019)

By Pat Mahon (June 2019)

In the cactus hobby, there seems to be one genus of easy-growing plants that reward us with gorgeous flowers in the spring: Echinopsis. Often taken for granted, most species and hybrids in the genus can quickly make specimen plants, are culturally forgiving and seem to give flushes of flowers.

Though mostly short-lived, echinopsis have elongated pedicels and large, trumpetlike flowers, whose presence typically dwarfs the plants. There is no shortage of hybrids available, with many colors and combinations. Once out of flower, echinopsis are practically indistinguishable from one another.

Instead of focusing on one species of Echinopsis, a sampling of its members can help us better understand the boundaries of the genus. First, Trichocereus is dead. The erroneous epithet is still used to describe trendy columnar cacti, but advances in taxonomy and technology (giving way to molecular systematics) have made Trichocereus and Lobivia victims of species delimitation shown to share a monophyletic relationship. Echinopsis is now the accepted generic name for these genera. A wonderful publication explaining the delimitation was published by Sofia Albesiano and Teresa Terrazas – see link below.

Echinopsis are restricted to South America, where they grow in very similar habitats. The name Echinopsis is derived from the ancient Greek “Ekihnos,” which is sea urchin; and “-opsis,” which means appearance. They prefer sandy and rocky substrates, typically growing on hillsides and in crevices. All of the species have fibrous roots and should have a very well-draining substrate to avoid rot. Some columnar species previously referred to as trichocereus are sometimes found among brush in wetter habitats.

Most Echinopsis species seem to tolerate and enjoy lower temperatures during the winter, and must be deprived of water during their winter rest in order to develop flowers in spring and summer. Once winter dormancy is broken, echinopsis should be grown in warmth, which is thought to influence flowering.

Although the flowers are incredible, they typically last about 24 hours, starting to bloom in the late evening. In summer, ensure plants get some water toward the evening. Never water cacti on the bodies in full sun! Almost all Echinopsis species grow in full sun, but in cultivation, slowly introduce the plants to increasing light to avoid sunburn.

Echinopsis oxygona
Most commonly referred to as the Easter cactus, this plant is usually on time with its name. A very globular cactus, it is fast-growing and pups freely. It is one of the most popular and easiest to grow species available.

Flowers may last around 36 hours indoors. Flower colors range from white to pink, and other colors are known. Native to southern Brazil, Paraguay, Uruguay, Argentina and Bolivia at elevations from 50 to 1,000 meters, this species generally represents what is commonly understood in form and shape for the genus.

Echinopsis ancistrophora subsp. arachnacantha (syn. Lobivia arachnacantha)
This smaller, clumping species is easy to grow and freely flowers if conditions are optimum. These are found with a myriad of colors and striping, and may include unknown or accidental hybridization. In any case, this species is highly recommended for any cactus hobbyist due to its small size, different-colored flowers and ease of cultivation. The plants are found in Bolivia and northern Argentina from 1,800 to 2,600 meters elevation.

Echinopsis pachanoi (syn. Trichocereus pachanoi)
Quite variable and distributed throughout the Andes, these columnar cacti are highly sought after for their attractive spines and dermal forms. They are found in higher elevations, from 2,000 to 3,000 meters. This is one of many former Trichocereus species that contains the psychoactive alkaloid mescaline.

Unless grown quite large, it is unlikely they will bloom in cultivation. Commonly used as a rootstock in grafts for slow-growing cacti scions, they are resilient to drought (or periods of non-watering) and exhibit fast growth. These plants are easily propagated by cuttings, and even when cut down can pup toward the base.

One of the most important discussions on Echinopsis concerns the boundaries that were delimited by including Lobivia and Trichocereus as a monophyletic treatment. Showing their close phylogeny, there are many hybrids incorporating former Lobivia and Trichocereus species.

If there is any similarity between these genera, it would be their ease of growth and maybe their prostrate branching, imbricate scales along the floral tube and subglobose fruits – but who cares about that! If you are not growing any of these Echinopsis, be aware it is very high up on the list for beginners and those who just enjoy cacti flowers.

Sources:
Cladistic Analysis of Trichocereus (Cactaceae: Cactoideae: Trichocereeae) Based on Morphological Data and Chloroplast DNA Sequences – https://www.researchgate.net/publication/280989243_Cladistic_Analysis_of_Trichocereus_Cactaceae_CactoideaeTrichocereeae_Based_on_Morphological_Data_and_Chloroplast_Dna_Sequences
Trichocereus.net – https://trichocereus.net/trichocereus-pachanoi-britton-and-rose-1920-echinopsis-pachanoi/
Echinopsis.com – http://www.echinopsis.com
JSTOR – Echinopsis, Lobivia, Rebutia: Where to Draw the Line –
https://www.jstor.org/stable/42787192?seq=1#page_sc_an_tab_contents
Llifle Encyclopedia of Cacti – http://www.llifle.com/Encyclopedia/CACTI/Family/Cactaceae/1041/Echinopsis_ancistrophora
http://www.llifle.com/Encyclopedia/CACTI/Family/Cactaceae/8376/Echinopsis_oxygona
Wikipedia – https://en.wikipedia.org/wiki/Echinopsis_pachanoi