• GENERAL BOTANICAL CHARACTERISTICS
• RAUNKIAER LIFE FORM
• REGENERATION PROCESSES
• SITE CHARACTERISTICS
• SUCCESSIONAL STATUS
• SEASONAL DEVELOPMENT

GENERAL BOTANICAL CHARACTERISTICS:

Letterman's needlegrass is a native, densely tufted, slender, perennial bunchgrass which often forms large clumps [15,17,18,27,30,38,39,40,63,65,66]. Old sheath bases of the culms are persistent [65]. This fine-stemmed, cool-season, erect grass grows from 6-60 inches (15-150 cm) in height [13,17,27,39,40,56,63,65,66]. Letterman's needlegrass has few spikelets [15], inflorescences are 2.8 to 7.5 inches (7-19 cm), and the awns are 0.5 to 1 inch (1.2-2.5 cm) long [27]. It has a fibrous root system and Woolley [66] found vertical root lengths of 35.4 inches (90 cm).

RAUNKIAER LIFE FORM:

Hemicryptophyte

REGENERATION PROCESSES:

Letterman's needlegrass reproduces by seed [40] and Ellison [21] characterized it as an "aggressive seed producer." In laboratory experiments most germination took place between 14 and 21 days after seeds were planted. Paulsen [40] observed that germination occurred between 77 and 86 degrees Fahrenheit (25-30 ^oC) in Colorado and average germination in greenhouse experiments was relatively low (47%). However, survival of the seedlings was high (90%) and the number of plants producing flowers was high (90%).

Needlegrasses (Achnatherum spp.) also reproduce by tillering [59].

SITE CHARACTERISTICS:

Letterman's needlegrass occurs across a wide range of elevations and exposures [1]. It is found on sandy loam, loam, silty clay loam, or clay loam soils [3,8,18,39]. It typically occurs on dry soils 15 inches (38 cm) or more in depth, but it can be found on very fertile soils or severely eroded ones [1,3,7,14,18,22,38,63]. It is commonly found on gentle slopes (3-10%) with a northern aspect [3,5]. The annual precipitation is 0.74 to 29.48 inches (188-749 mm) [5,13,17,22,39,40,51,67]. The average annual temperature where Letterman's needlegrass is found in Utah is 32.5 to 42.6 degrees Fahrenheit (.28-5.89 ^oC) [13]. The average maximum temperature in Utah (1935-1944) was between 55.8 and 73.2 degrees Fahrenheit (13.2-22.9 ^oC) and the average minimum temperature was between 12.1 and 36.9 degrees Fahrenheit (-11.1-2.7 ^oC) [22]. For Colorado, the average temperature ranges from 34 to 65 degrees Fahrenheit (1.11-18.3 ^oC) [40]. It is described as somewhat more drought-resistant than the closely related Columbia needlegrass [63].

Letterman's needlegrass occurs from middle elevations to the subalpine zone [15]. Elevation ranges are as follows:

4,290 to 4,950 feet (1,300-1,500 m) in California [2,12]
2,365 to 12,500 feet (1,700-3,810 m) in Colorado [7,14,18,33]
7,200 to 8,500 feet (2,195-2,591 m) in Oregon [46]
4,918 to 11,705 feet (1,617-3,355 m) in Utah [3,5,13,18,22,24,35,37,39,41,43,57]
6,388 to 10,100 feet (1,947-3,081 m) in Wyoming [51]

SUCCESSIONAL STATUS:

Letterman's needlegrass is a climax species in a number of grassland, sagebrush, mountain-shrub, and pinyon-juniper (Pinus-Juniperus spp.) communities. It also grows well in early successional assemblages, and is well represented in many early- to late-seral plant associations [53]. Reid [46] found Letterman's needlegrass on severely eroded sites in Oregon where greenleaf fescue (Festuca viridula) had died. This species is an invader on disturbed sites and one of the 1st persistent perennials to invade eroded sites dominated by mountain tarweed (Madia glomerata) [22,42,46].

SEASONAL DEVELOPMENT:

Most needlegrasses begin growth in the early spring [61]. Specific phenological data for central Utah are given below (average dates for 1925-1934) [13]:

Elevation (ft)	Plant 6 in. tall	Flowerstalks evident	Flowerheads showing	Flowers in bloom	Seeds ripe	Seeds dispersed
7,150	May 16	May 25	June 15	July 1	July 28	Aug. 14
7,655	May 21	May 29	June 22	July 5	Aug. 2	Aug. 21
8,450	June 6	June 3	June 23	July 6	Aug. 6	Aug. 26
9,000	June 19	June 19	July 7	July 21	Aug. 23	Sept. 21
10,100	July 21	June 21	July 9	July 25	Aug. 28	Sept. 19

In a western Colorado mountain grassland site, flower development took place between June 20 and August 19. Seeds matured and were disseminated between July 10 and September 6 [40].

Related categories for SPECIES: Achnatherum lettermanii | Letterman Needlegrass