Sclerocactus

Sclerocactus
Sclerocactus wrightiae
Scientific classification
Kingdom:	Plantae
Division:	Magnoliophyta
Class:	Magnoliopsida
Order:	Caryophyllales
Family:	Cactaceae
Subfamily:	Cactoideae
Tribe:	Cacteae
Genus:	Sclerocactus Britton & Rose
Species
Sclerocactus blainei Sclerocactus brevispinus Sclerocactus cloverae Sclerocactus glaucus Sclerocactus mesae-verdae Sclerocactus nyensis Sclerocactus papyracanthus Sclerocactus parviflorus Sclerocactus polyancistrus Sclerocactus pubispinus Sclerocactus sileri Sclerocactus spinosior Sclerocactus wetlandicus Sclerocactus whipplei Sclerocactus wrightiae

Sclerocactus ("hard cactus", from Greek; refers to the hard, dry fruit) is a genus of cacti. It comprises about 15 species, the exact number depending on the authority. These species are very xerophytic. They are sometimes called 'fishhook cactus' or 'little barrels'.

Description

Sclerocactus are ovoid to elongate cylindric, have rigid stems with tubercles that are generally coalesced into ribs, and are covered with spines that come out of the areoles. Most species have at least one hooked spine at each areole. Less often, species may not have hooks.

These plants are found in higher elevation deserts such as on the Colorado Plateau, or in the Mohave Desert or the Great Basin. They are well suited to extremes due to lack of rainfall, hot summers and below freezing winters.

S. parviflorus growing on its side with wood debris nearby

The fishhook cactus typically grow in areas where water flows irregularly or depressions where water can accmulate for short periods of time. They are most often found growing along washes and arroyos where their seeds have been subjected to scarfication due to water movement, but they oddly also tend to grow along ridges in spots where depressions have formed and can hold water for some period of time.

The "fishhook" spines and the armored web of spines enclosing the cactus body in this species is an adaptation which allows the plant to move to more favorable locations. This plants seeds germinate in areas where water movement occurs or in areas where standing water accumulates for some period of time, and during flash floods, the hooked spines allow the plants to be caught on water bourne debris and be uprooted and carried to areas where water tends to accumulate. A large percentate of plants in habitat show signs of water damage along the stems which has healed and are found growing on their sides in places where floodwaters have deposited them. The habitat these plants exist in is very arid, and the plants have adapted to exploit water movement to concentrate their biomass in areas where water is likely to be present.

Species

• Many species of Sclerocactus are protected under the provisions of the Endangered Species Act and all species should be treated as imperiled.

• Sclerocactus parviflorus is the most common species; its flowers are usually pink, but are yellow in a few areas (see photo) or, rarely, white or intermediate shades.

These two species were first collected by Andrew Lafayette (A.L.) Siler in Southern Utah/Northern Arizona, who lived in Kanab, Utah, at the time:

• Sclerocactus polyancistrus is the ‘giant’ of the genus. Some species are quite rare and need considerable further study.
• Sclerocactus sileri is sometimes confused in nomenclature with Pediocactus sileri, because of the same specific epithet.

Synonymy

• Sclerocactus was once reduced to synonymy with Pediocactus—but this is not accepted; these genera are not closely related.

The following genera have been brought into synonymy with Sclerocactus and this is commonly accepted:

• Coloradoa Boissev. & C.Davidson
• Toumeya Britton & Rose

The following have been proposed for synonomy with Sclerocactus but this is controversial. They are closely related, as shown by molecular genetic and other research:

• Ancistrocactus Britton & Rose
• Echinomastus Britton & Rose
• Glandulicactus Backeb.
• Homalocephala Britton & Rose

Cultivation

Sclerocactus adapt easily in cultivation. They are a cold adapted species, and in habitat they normally grow in very arid areas which are subjected to deep cold in spots where water flows irregularly or depressions where water can accmulate for short period of time. They are most often found growing along washes and arroyos where their seeds have been subjected to scarfication due to water movement, but they oddly also tend to grow along ridges in spots where depressions have formed and can hold water for some period of time.

They do most of their growing in the spring and benefit from moderate fertilizer. They prefer mineral based soils about 1/2 sand mixed. They are tolerant of over watering provided they are grown in small pots that drain and dry out quickly. They do best out of doors and prefer very bright light and do best in full sunlight. They are not particularly attractive plants and their vicious hooked spines are a real problem in traffic areas of a home. They are best kept out of doors where they tend to thrive. Like Pediocactus, Sclerocactus "deflate" in late fall in preparation for winter and freezing and will push water out of the plant body through the roots back into the soil and dramatically decrease in size. They require deep cold and dormancy to bloom well, and best practice if you live in an area with cold winters is to place them in a dry place with bright light subjected to freezing temperatures.

Some species, such as S. Parviflorus, produce large, showy flowers and put an a short, but impressive floral display in early spring.

Propagation

Sclerocactus seeds are difficult to germinate as they contain inhibitors, and require cold stratification, prolonged soaking, or scarification of the seeds to trigger germination. Seeds of members of this genus can take up to three years to germinate in some cases if not scarified or subjected to repeated freeze and thaw cycles in the presence of water. Best practice is to sow the seeds in the fall in trays of moist mineral soil left outdoors overwinter covered with a window screen in a protected area. Sclerocactus are very easy to grow and maintain in cultivation, but have a reputation for being difficult to grow from seed.

External links

• Southwest Colorado Wildflowers
• Utah Rare Plant Guide