Monographs Details: Hackelia cusickii (Piper) Brand
Authority: Gentry, Johnnie L. & Carr, Robert L. 1976. A revision of the genus Hackelia (Boraginaceae) in North America north of Mexico. Mem. New York Bot. Gard. 26: 121-227.
Description:Species Description - Moderately slender perennial, (10-)20-50 cm tall, the woody caudex tightly clothed with old stem and leaf bases; stems several from a slender taproot, erect or ascending, antrorsely strigose in the inflorescence, retrorsely strigose near the base; stem bases, radical and lower cauline leaves bearing scattered cilia. Leaves strigose, greyish-green, pubescence of 2 distinct size ranges (0.5-0.6 mm and 0.1-0.3 mm); radical leaves very many, (5-)8-16 cm long, (4-)8-16 mm wide, narrowly elliptic and petiolate up to 1/2 their length, acute; cauline leaves few, reduced upwards, becoming sessile and lanceolate, lowermost 8-10 cm long, 4-10 mm wide, narrowly elliptic and petiolate, reduced to 4-6 cm long, 5-9 mm wide at base of inflorescence; bracts lanceolate, much reduced. Pedicel 6-7 mm long in fruit. Calyx acute, 4-5 mm long. Corolla limb blue with a yellow (sometimes very light) throat, (5-)7-10(-13) mm wide. Fomices with appendages papillate-puberulent, emarginate. Anthers 0.8-1 mm long. Nutlets 3.0-4.3 mm long, narrowly triangular; dorsal surface verrucose-hispidulous, the intramarginal prickles prominent, 8-15, these usually less than 1 mm long; prominent marginal prickles distinct to their bases or nearly so, linear-lanceolate, 1.4-2.4 mm long, these generally alternating with l-2(-3) short prickles (< 0.7 mm long). Chromosome number, 2n = 48.
Discussion:Lappula cusickii Piper, Bull. Torrey Club 29: 542. 1902.
Lappula arida var cusickii (Piper) Neis. & Macbr., Bot. Gaz. 61: 41. 1916.
Hackelia arida var cusickii (Piper) Johnst., Contr. Gray Herb. 68: 48. 1923.
Type. OREGON. Logan Mountains, July 1, 1901, Cusick 2623 (holotype, WS!; isotypes, ORE!, UC!).
Hackelia cusickii is a uniform taxon of sharply limited habitat. It is found in the thick duff layers under Juniperus species. A further requirement is that the juniper has low crowded branches providing a very dense canopy. Although the reason for this unique relationship is not known, there is little doubt that the factors of shade and moisture play a role. These factors alone, however, may not explain why the plant is restricted to the Juniperus habitat, as there are other species within the range of Hackelia cusickii that would seem to provide similar shade and moisture regimes (Pinus ponderosa, Artemisia tridentata, etc.).
There is a possibility of a biochemical interaction between Hackelia cusickii and the juniper. This could take the form of a direct interaction; i.e., stimulatory effect on the growth of H. cusickii due to a chemical exudate of the living juniper plant or its organic detritus; or, an indirect interaction; i.e., juniper by-products having an allelopathic effect on other herbs in the area, thus reducing potential competition for H. cusickii. Allelopathy is apparently quite widespread in the plant kingdom and has been shown to be an important factor affecting plant distribution in arid areas (Muller, 1966). Hackelia species are in general very poor competitors and are therefore often restricted to disturbed habitats. Because of this, one might predict that the factor restricting H. cusickii to the juniper understory is the reduced competitive stress at that site, regardless of the mechanism involved.
Because of its unique habitat requirements Hackelia cusickii is somewhat limited in range. It is found in the foothills of the Blue Mountains of central Oregon, localized on buttes and mountains of south-central Oregon, and at scattered sites in the high plateau of northeastern California. Although reported from lower elevations, the taxon is usually restricted to sites above 4000 feet.
Morphologically, Hackelia cusickii appears most closely related to H. diffusa var cottonii, the distribution of which nearly reaches the range of H. cusickii in west-central Oregon.
Three Idaho specimens which are doubtfully included in Hackelia cusickii are: Trelease 4869, Shoshone Falls, Twin Falls Co. (MBG); Baker 8192, ridge between War Eagle and Cinnibar, Silver City Range, Owyhee Co. (ID); Larrison and Jollie s.n., 8 miles NE of Riddle, Owyhee Co. (ID). Because these specimens do not represent adequate material and are located outside the normal range for the species, we are referring them here subject to further study. The specimens appear to differ from typical H. cusickii only in minor morphological features, but because such variation is unusual in this taxon, there is some question as to their placement. Further collecting may demonstrate that H. cusickii is common in this area of SW Idaho and SW Oregon, where suitable habitat is available. An alternative possibility is that these specimens are merely unusual forms of H micrantha, perhaps the result of grazing.
The Sweetser collection labeled “Huntington, Oregon” appears to be Hackelia cusickii, but there is some question as to the accuracy of the collection site. Huntington is considerably outside the normal range for the species and the area provides little suitable habitat. Until we can survey the area more completely, we prefer to include this collection as a disjunct population site for H. cusickii.
Distribution:United States of America North America