Arizona Stonecrops & Rock Mat
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Graptopetalum bartramii: Mature leaf rosette with single flower.
Derwent drawing pencils on Strathmore Toned Gray paper, 11" x 12". Lorena.B. Moore, 2013.
Graptopetalum bartramii: Young plants in granitic gravel.
Graptopetalum bartramii & Graptopetalum rusbyi
Graptopetalum ("writing petal") is a small genus in the Stonecrop Family (Crassulaceae), endemic to Mexico and Arizona. The rosettes of thick, succulent leaves look similar to those of its close relatives Echeveria and Dudleya, but the flower petals are yellow with distinctive red spots. Both species often grow with Sedum cockerellii (shown below) which is in the same family. The two U.S. species are restricted to Arizona and are protected as Salvage Restricted by state law. Although they prefer similar habitats, they usually occupy different mountain ranges and elevation/vegetation zones. Both species are reported for the Rincon Mountains and there may be other localities where they are found together. A comparison between the two species is presented below to aid in identification.
Both species are larval food plants for the Xami Hairstreak butterfly. See photos of the larvae, mature insects, habitat, and food plants HERE on the Butterflies of North America website.
Bartram's Stonecrop; Patagonia Leatherpetal
STATUS: Sensitive species (BLM, USFS)
Endangered Species CANDIDATE (USFWS) under review as of 2012. Federal Register Notice
RANGE: Found in fewer than twenty localities in the southeastern Arizona mountains; one documented locality in northern Sonora, Mexico. Known from the Santa Rita, Rincon, Empire, Patagonia, Mule, Baboquivari, Chiricahua, Atascosa/Pajarito Mts. (Tumacacori Highlands).
HABITAT: Prefers granitic rocks (including rhyolite); not known from limestone. Found at 4000-6000 feet in encinal (oak grassland) and Madrean oak-pine woodland. Plants grow in moist, partly shaded, organic-rich pockets of soil on outcrops, among boulders and coarse gravel, or on the downhill side of a sheltering shrub, often on north-facing slopes with Selaginella (spikemoss) and/or well-developed cryptobiotic soil crust.
NATURAL THREATS: This plant is inherently rare for several reasons. It requires sheltered locations with good drainage but a humid microclimate, typically in rocky canyons, so suitable localities are small (sometimes tiny) and uncommon. Natural reproductive rates appear to be low, and several localities have few or no reproducing plants. Plants are vulnerable to drought, fire, and flooding.
HUMAN THREATS: Drainage alteration due to development, roadwork, mining, or other construction projects. Trampling by humans and cattle. Destruction (often labelled "development" or "improvement") of springs and creeks, removing the source of water and humidity for individual plants and their immediate habitat. Although G. rusbyi (like several Mexican Graptopetalum species) is cultivated and legally available from cactus nurseries, G. bartramii is not cultivated and thus is vulnerable to collection and destructive "research".
G. bartramii with drought and frost damage, spring 2010.
Rusby's Stonecrop; San Francisco Leatherpetal
RANGE: Central Arizona (near Superior, etc.), Pinaleno, Santa Teresa, Santa Catalina, Rincon, Waterman Mts. Several mountain ranges in Sonora, Mexico.
HABITAT: Granitic rocks (especially granite gneiss), rarely limestone (Waterman Mts.) Grows in part shade in sheltered rock crevices or on damp outcrops, often with Selaginella, soil crust, and desert ferns. Saguaro desert upland, desert grassland, canyons with saguaros and Mexican blue oak, 2500-4000 feet.
THREATS: Similar to G. bartramii but less critical. G. rusbyi is more common, has a larger range, and is cultivated (as of 2012, plants were available from several nurseries in Tucson). Its clustering growth habit and preference for lower elevations may make it more drought tolerant than G. bartramii, and its habitat is less vulnerable to fire.
GRAPTOPETALUM PHOTO GALLERY
|FLOWER BUDS in late August.||LEAVES: Broadest near the tip, light bluish-green.|
|FLOWERS on October 16, 2007. Open flowers are about 1 cm across.|
|SEEDPODS persist until the next flowering season.|
|Graptopetalum rusbyi on granitic gneiss (left and center) and limestone (right) at about 3000 feet.|
|FLOWERS on May 1, 2005. Open flowers are .5 to .75 inches.|
Dudleya pulverulenta ssp. arizonica (= Dudleya arizonica)
in central Arizona. Blooms in May. Range overlaps with Graptopetalum
rusbyi, but Dudleya grows at
lower elevations and its rosettes have larger leaves.
Locally common on shady outcrops of many rock types in desert grassland and chaparral, Madrean evergreen woodland, and ponderosa pine woods, from 3500-8000 feet. Blooms in July-September.
are tiny but thick. This cluster is the same
diameter as a single large Graptopetalum rosette.
This unusual plant
resembles a succulent but is actually a miniature evergreen shrub in the Rose
It grows in full sun on bare dry limestone or marble throughout much of the mountain West, ranging as far north as Montana.
It is uncommon in southern Arizona and is found only on high outcrops in a few mountain ranges.
Known from the Huachuca, Whetstone, and Empire Mountains.
Some populations may be vulnerable to mining (limestone/marble quarrying for concrete) and development.
|Anchored in deep cracks, plants form small mounds on bare limestone.||Dead plants look like tiny gnarled trees.|
white flowers bloom in late
summer. Seedstalks shown above.
|The evergreen leaves are light bluish green.||
Leaf rosettes have tiny silky white hairs.
TEXT, and WEBPAGE created by Lorena B. Moore. UPDATED 1/1/2013
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