Astrophytum ornatum

Ribs, areoles and spines of Astrophytum ornatum.
Ribs, areoles and spines of Astrophytum ornatum. Photo Konrad Szychowski.

Name and identification

Astrophytum ornatum (DC.) Britton & Rose is accepted in POWO. The basionym Echinocactus ornatus was published in 1828, and the accepted combination in 1922. Strong, rigid spines and an increasingly columnar body distinguish the plant. White hairs often form transverse or diagonal bands. [2-WWW] [Szychowski b.d.b] [Bartylak 2007]

Stem, spines and development

This is one of the largest members of the genus. The archived description gives plants about a metre tall and up to 30 cm in diameter, usually with eight ribs and five to eleven strong spines. Older cultivated specimens need space for their heavy, elongating bodies. Ribs may run almost straight or spirally, and their number and shape change with development. Spine colours include yellow and brown, becoming grey later. [Bartylak 2007] [Anonim b.d.e]

Hairs may form distinct bands or cover more of the surface. Some hairs disappear from older stem portions. A greener lower part of an old plant alone therefore does not establish a distinct variety. The names mirbelii, glabrescens, virens and niveum are retained in the historical index. [Bartylak 2007] [2-WWW]

Flowers, fruits and seeds

Flowers open during the day and are yellow, usually without a distinctly red throat. In the archived description they reach 7–9 cm in diameter. Flowering depends on maturity and cultivation conditions. Archived materials describe later flowering than in many small astrophytum plants, but give no universal number of years to maturity. Green, partly drying fruits open at the apex. [Szychowski b.d.c] [Anonim b.d.e] [Bartylak 2007] [Montanucci 2009]

The 2012 seed study used material from Hidalgo. Seeds floated very well. After 30 days, 90% with the layer of funicular remains intact still floated, and 100% after its removal. Germination was nevertheless low, particularly with submergence or a thin water layer. Floating and germination are separate stages of seed life. [Sánchez-Salas et al. 2012]

Range and ecology

POWO lists northeastern Mexico through to Veracruz. Field and cultivation materials describe rocky limestone slopes in Hidalgo and Querétaro, among other sites. In the 2016 comparison, A. ornatum occupied cooler, wetter conditions on average than A. capricorne. Mean elevation of 56 records was 1498.7 m above sea level, with a standard error of 49.9 m. [2-WWW] [Bartylak 2007] [Carrillo-Angeles et al. 2016]

Association with a wetter climate does not imply tolerance of a constantly wet pot. Water drains on a slope, and roots use spaces and oxygen conditions different from those in a container. This difference matters when transferring habitat descriptions to cultivation. It is a practical inference from the habitat and cultivation recommendations. [Bartylak 2007] [Szychowski b.d.c]

Cultivation in Poland

A bright, airy site, stable pot and permeable substrate are needed. Water during growth after the mixture dries. Heavy fertilisation and excessive hydration can cause unwanted elongation of soft growth. The archived account recommends restrained cultivation. [Szychowski b.d.c] [Bartylak 2007]

Bartylak recommends overwintering above 10°C and associates excessively low temperature with brown epidermal injury. This grower's specific recommendation is useful as a cautious starting point in Poland. It is not a laboratory-defined tolerance threshold. The 6–10°C range shared by some members of the genus should not automatically be applied to every A. ornatum. [Bartylak 2007] [Szychowski b.d.c]

The species is propagated by seeds. Repotting older plants requires body support and root protection, avoiding a grip on the spines. For grafted specimens, Wery listed rootstocks named Trichocereus spachianus, T. bridgesii and Eriocereus jusbertii. These names come from the cited historical material. Rootstock choice requires consideration of its own growth and overwintering needs. [Szychowski b.d.c]

Similar plants

Rigid spines and banded hairs help identify A. ornatum. Forms with few hairs retain other species features. Hybrids with A. myriostigma can combine both parents' features. OR–MY or MY–OR in a collection should be supported by information about the cross performed. [Szychowski b.d.a] [Bartylak 2007] [11-WWW]