G108 



DROPSEEDS 



Sporo' bolus spp. 



The dropseeds, a large genus of the redtop tribe (Agrostideae), 

 containing about 36 species in the United States, are chiefly peren- 

 nials, but a few species are annuals. Both the common and scientific 

 names of the genus refer to the prompt dropping of the seed as it 

 ripens (Greek spora, seed, and ballein, to cast forth). 



These plants grow mainly at lower elevations on desert, semi- 

 desert, and plains. They are especially common in the Southwest 

 and form a very important part of the forage on the lower ranges. 



Most of the dropseeds are bunchgrasses, but a few of the perennial 

 species, such as Mississippi dropseed, or rushgrass (S. inacrus} and 

 seashore dropseed, or rushgrass (S. virginicus), have creeping root- 

 stocks (rhizomes). Practically all of the dropseeds produce an abun- 

 dance of fairly viable long-lived seed, but the seed coats of mosb 

 species are almost impervious to water and, when used in artificial 

 reseeding, should be scarified for best results. Jackson 1 found that 

 scratching or pricking the seed coats of Sporobolus seeds hastened 

 germination greatly. Soaking affected the seed coat but little, and 

 shaking in sand, even for 9 hours, had little effect. Alkali sacaton. 

 Avas the only dropseed tested which did not require puncturing the 

 seed coat for good germination. 



The large number of range dropseeds, their wide distribution, and 

 the local abundance of several species give this genus a rather high 

 forage rating, especially in the Southwest. Many of the dropseeds 

 are good-sized, leafy grasses, and produce a large volume of forage. 

 In general these plants are iairly palatable, although the foliage of 

 most species tends to be rather too coarse to rank with that of some 

 of the choice range grasses. However, black dropseed (S. inter- 

 ruptus] is an exceptionally good species, highly relished by live- 

 stock, and on some ranges sand dropseed (S. cryptandv'us) is rated 

 as very good forage. A few species are so coarse and harsh that they 

 are of little value as forage except while young. The palatability of 

 dropseeds is greatest while the plants are young and succulent, but, 

 as they cure well on the ground, the perennial species which do not 

 become too harsh when mature furnish good winter forage. Some 

 dropseeds are important on certain ranges because they thrive on 

 dry, alkaline soils where other grasses will not grow. The few 

 annual species of dropseed on our western ranges are unimportant as 

 forage plants. They are small, low in palatability, and their abun- 

 dance, depending upon the variation in climatic conditions, is very 

 uncertain. Even during favorable years their -forage production ia 

 very low. 



The flower heads (panicles) of the dropseeds are either spreading 

 or spikelike. The small flowers and "seeds" are borne singly on a 

 slender stem (in one-flowered spikelets), the "seeds" falling readily, 

 leaving the empty lowest two flower bracts (glumes) attached to the 



1 Jackson C V. SEED GERMINATION IN CERTAIN NEW MEXICO BANGS GRASSES. Bot. 

 Gaz. 86 : 270-294, illus. 1928. 



