Penstemon haydenii

Adapted from Freeman (1981), Weedon et al. (1982a) Stubbendieck et al. (1982), and Lichvar (1982): Distinguished from P. grandiflorus by blue corolla rather than pinkish, and long, narrow leaves rather than roundish. Distinguished from P. angustifolius by its larger, lighter blue flowers rather than the smaller, darker blue flowers of P. angustifolius. Penstemon haydenii is noted by strong, fragrant odor (Weedon et al., 1982). Also, P. grandiflorus has never been observed in or on the rims of blowouts (Stubbendieck et al., 1982).

Penstemon haydenii inhabits early successional, sparsely vegetated, sand dunes with depressions created by wind erosion referred to as blowouts (Heidel 2022). In Nebraska, these are found in sandhills prairie (Stubbendieck et al. 1989, Kuchler 1964, Pool 1914). The term 'blowout' refers to a naturally occurring depression in the Nebraska Sandhills. These depressions are caused when vegetation at the upper slope of a hill is disturbed, typically by fire or grazing animals. The 'blowout' may take as many as ten years to become a full scale and active blow out. The process is started when sand is deposited from the windward side of the slope to the leeward side, and this process continues until eventually the roots of the surrounding vegetation are exposed and finally ripped up by the force of the wind. Eventually, a crater is created where there is constant wind action, so succession is continually taking place (Stubbendieck et al. 1989). As a pioneer species, it establishes within the blowout, usually near the leeward side only, after the sand has stabilized, but it declines once vegetation (prairie grasses and forbs) establish and the blowout begins to "heal" (USFWS 2022).

All sites have less than 10% basal ground cover (Heidel 1981). Initial colonization of dunes is by Redfieldia flexuosa. Psoralea lanceolata, Redfieldia flexuosa, and Calamovilfa longifolia are common associates in Nebraska and Wyoming (Heidel 1981, 2022). Other associated plants include Andropogon hallii (NE only), Artemisia campestris, Asclepias arenaria, Astragalus longifolia, Calomovilfa longifolia, Cirsium plattensis, Helianthus spp., Hymenopappus corymbosus, Lathyrus polymorphus, Linum sulcatum, Lithospermum incisum, Lygodesmia rostrata, Muhlenbergia pungens (NE only), Oenothera serrulata, Oryzopsis hymenoides, Petalostemum villosum, Rumex venosus, Tradescantia occidentalis, and Yucca glauca (Heidel 1981, 2022, Lichvar 1982).

Penstemon haydenii is well adapted to survival in blowout dunes habitat. It can recover from sand burial (Barr 1944) and develop adventitious roots from buried stem and leaf nodes (Barr 1951). Habitat erosion and shifting sand can expose the seed bank, prompting seed germination (Heidel 2022). The nearly horizontal rootstocks produce numerous fibrous roots, providing strong anchorage in the sands (Weedon et al. 1982). Colonization is primarily by seedlings, which take 3 or more years to establish. Barr (1951) noted that a seedling 4-5" tall often has roots over 1' long. Established plants, and even seedlings to some degree, can tolerate burial by sands, sending up new shoots from the crown; this suggests this species may be long-lived (Heidel 2022). Bees are the primary pollinators (Weedon et al. 1982, Tepedino et al. 2006, 2007). Penstemon haydenii appears to bloom in alternate years, and this may be tied to moisture cycles (Stubbendieck, pers. comm.). While in bloom, P. haydenii produces large quantities of seed. Seed weight is 125,000 per pound (Stubbendick et al., 1982). Barr (1946) believed that the tendency to bloom profusely in certain years makes the plant vulnerable to weather conditions and local extinctions. Its life history appears tuned to recurrently invading newly formed blowouts (Weedon et al., 1982), and it declines under competition from other colonizing species (Weedon et al., 1982; Lichvar, per. comm.), particularly Andropogon hallii (Stubbendieck, pers. comm.). Freedom from moisture competition may be significant (Barr 1951).

Artificial propagation studies are underway. The following results are from Stubbendieck et al. (1982, 1983). Seeds were collected in August 1981 in Garden County, Nebraska from the largest known population. Stubbendieck et al. (1982) found that scarification (especially removal of the radicle end of the seed) increased germination success from the normal 10% to 60%. Allowing seeds to inbibe water 12 to 24 hours prior to scarification improved germination success to 90-95% and may indicate the presence of a water-soluble inhibitor (Stubbendieck et al., 1982). Seedlings were grown in tubes in the greenhouse for approximately 90 days. In May 1982, 297 transplants were placed into blowouts in Cherry, Thomas and Grant counties. At each blowout site, 33 plants were placed at each of 3 locations: in the depression or area of sand removal; on the leeward side of the rim; and on the windward or sand deposit side of the rim. A fourth location was on disturbed, bare sand near the Platte River in Phelps County, Nebraska (Stubbendieck et al., 1982). There was a 90% survival rate 3 weeks after transplant (Stubbendieck et al, 1982). Cattle trampling appears to have destroyed most of the seedlings in the blowout depressions at two locations. The survival rate at the end of the first growing season for remaining transplants was 83% (Stubbendieck et al., 1983).

This species is mycorrhizal with an AM fungus in the fine endophyte group, Glomus tenue, identified on fine roots of a juvenile plant (Heidel 2022).

The Blowout Penstemon reproduces most frequently by vegetative propagation (Caha et al. 1998). It is believed to be self-incompatible, and requires pollinators for pollination to take place and to produce seed (Tepedino et al. 2007). Rodents may be one method of seed dispersal (USFWS 2012), but the seeds have appendages that would aid in wind dispersal of what is a relatively large and heavy seed amongst the dune species (Heidel 2022).. Seeds under deep substrate, in the seedbank, do not germinate until habitat erosion exposes them (Tilini et al. 2017, Heidel 2022). Seedlings take three or more years to become established plants (Heidel 2022).