| BEN |
| BOTANICAL ELECTRONIC NEWS |
|---|
| ISSN 1188-603X |
| No. 525 March 9, 2018 | aceska@telus.net | Victoria, B.C. |
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Accompanying Plate: http://mpb.ou.edu/ben/525/ben_525_plate.pdf
In 2013 the Central Okanagan Naturalists' Club began cataloguing the plants at a site in West Kelowna which contains a high diversity needing conservation attention. In April 2016, while snow was still on the ground, the authors noticed Steer's Head (Dicentra uniflora Pursh) growing at the site.
Steer's Head is a small perennial member of the Papaveraceae (Poppy) family (The Angiosperm Phylogeny Group 2016). It was formerly placed in the Fumariaceae (Fumitory) because members are generally quite distinct from other members of Papaveraceae (Stern, 1997). From a molecular and an evolutionary perspective, however, it is preferable to include it in the Papaveraceae.
Its unique flowers range in colour from whitish to pinkish suffused with light brown. The two outer petals sharply curve backwards to form the horns of a steer while the two straight inner petals form the snout, being wider near the base and narrowing to a purplish, rounded tip (Figure 1). The flowers and the leaves grow on separate stems. From 4 to 7 leaves with 3-4 orders of leaflets and lobes, with whitish waxy powder on the underside, hug the ground (Figure 2). The fruit is an ovoid-ellipsoid capsule from 10 to 12 mm long (Figure 3). The leaf and flower stems grow from a club to spindle-shaped tuber located 8 to 15 cm below the surface (Figure 4). Small bulbils are often present on the tuber near the stem.
>From April 18-28, 2016, we found 18 Steer's Head flowering at a hillside location near Crystal Mountain Ski Resort. The plants were growing on sloping terrain in light brown mineral soil containing small pebbles (< 1 cm). The snow was melting in the area. We noticed that once the seedpods began to develop the plants appeared to stop growing and then withered within a month. The ground cover was sparse with no consistent plant association among the sites with Steer's Head. Within a 1 m radius of the Steer's Head plants we observed: Small-flowered Blue-eyed Mary (Collinsia parviflora), Swale Desert-parsley (Lomatium ambiguum), Silvery-brown Pussytoes (Antennaria luzuloides), Yellow Bell (Fritillaria pudica), Compact Selaginella (Selaginella densa), Yarrow (Achillea millefolium), Stonecrop (Sedum sp.), Wild Strawberry (Fragaria virginiana), Buckwheat (Eriogonum sp.), Old Man's Whiskers (Geum triflorum), Naked Broomrape (Orobanche uniflora), Great Basin Nemophila (Nemophila breviflora), Dwarf Waterleaf (Hydrophyllum capitatum), Narrow-leaved Montia (Montia linearis), grasses and a few lichens and mosses.
In 2017 we began searching in early April and widened our search area. The ground was completely snow covered until mid-April when patches of bare ground began to appear. We recorded the first Steer's Head leaves on April 26 and the first flowers on May 5. We found hundreds of plants over parts of a 5 square km search area but fewer than 50 with flowers despite several return visits. The plants grew at elevations 1180 to 1320 m a.s.l. in a variety of habitats including on pebbly soils, as we observed in 2016, moss covered areas, and next to rocks and rotting branches. They were usually on a sloping area but in a few instances on relatively flat ground near the top of a slope. Fresh flowers stood upright for only a few days and then collapsed to the ground due either to rain or snow and/or to the weight of the rapidly developing seed pod.
The majority of the Steer's Head plants we found in 2016 and 2017 did not have flowers. Bulbils and small tubers likely require several years to store sufficient energy for flower production. When it became apparent that many plants were spread over a wide area and that limited collection would not endanger the population, we collected six plants. Some we pressed and others we dissected. We noted that the seed pods developed within a few days of the flower emerging, and that a single, green-coloured pod was produced that filled the entire inner 'skull' space of the flower. One mature capsule contained 58 kidney-shaped seeds. Mackey & Schlising (2013) reported an average of about 70 seeds per flower in Northern California. Based on 6 plants that we collected, the root tubers were found from 8 to 15 cm deep in the soil. A herbarium voucher (collection number JPV 007) was deposited at the University of British Columbia.
Steer's Head typically grows from very early spring to late summer on rocky slopes and hillsides in gravelly soils at 1500-3300 m a.s.l., often near the edges of melting snow banks, and has been found in California, Idaho, Montana, Nevada, Oregon, Utah, Wyoming, Washington, and BC (Stern 1997). This plant should be attributed to Colorado as well (Weber & Wittmann 2012). Steer's Head is considered common to secure in most of the nine states where it occurs. In Canada it is only found in extreme southern British Columbia and is red-listed as S2 in British Columbia when it was last assessed in 2015 (Penny 2016).
There have been 15 reports of Steer's Head in British Columbia: 3 from the Armstrong-Kelowna area, 4 from the Rossland-Salmo-Castlegar area, 2 from Grand Forks, 4 from E. C. Manning Park area, and 1 each from the Merritt and Creston areas (UBC Herbarium online database, 2017; Underhill 1967; Meyer 2017). The first report of Steer's Head was from Phoenix, near Grand Forks in 1904. Both the 1933 and 1941 Armstrong sightings are considered historical (Douglas et al. 2002) and according to the coordinates given for these records, the area is now a sports field associated with a school. Therefore, the 2017 Cabin Lake sighting near Merritt is the most northerly within the range of Steer's Head. The Creston & E. C. Manning records define the east and west boundaries respectively.
Little is known concerning the basic biology and reproduction of Steer's Head. Bees appear to be the main pollinator (Ley et al. 2011). When the seed pod matures it dehisces on the ground and the seed is dispersed by ants (i.e. myrmecochory). The plant also reproduces vegetatively via its bulbils (Berg 1969). It is host plant to the American Apollo butterfly (Parnassius clodius) which has only been seen in the Okanagan valley from a location 95 km southwest of the Crystal Mountain Ski Resort (St John 2017).
Elevation has a strong influence on the flowering dates for Steer's Head. In British Columbia an increase in elevation of 637 m, 673 m, and 1093 m delayed flowering by as much as 7 weeks (Table 1). Mackey & Schlising (2013) reported that increases in elevation of 600 m and 628 m at two locations in northern California delayed leaf-out, flowering, and seed production by 3 to 4 weeks. The disappearance of snow cover is critical as well. At the West Kelowna location, we observed a 16 day delay in first flowering in 2017 from 2016.
Table 1. Flowering dates in 2017 for Steer's Head (Dicentra uniflora) from one location in northern Washington and four locations in southern British Columbia
| Location | Elevation (m) | Flowering date | Reporter |
|---|---|---|---|
| Sam Hill, WA | 425 | April 6 | Jack Mynatt |
| West Kelowna, BC | 1210 | May 5 | Courtney & Scotter |
| Lloyd's Meadow, BC | 1174 | May 10 | Ryan Batten |
| Cabin Lake, BC | 1847 | June 28 | Acacia Meyer |
| Punk Mountain, BC | 2267 | July 1 | Ryan Batten |
We noted that depth of the plant's tubers below the surface likely protects them from forest fires and many surface disturbances such as moderate erosion and some human activities. However, this also likely limits its distribution in our study area where shallow bedrock is with thin to no soil in some areas.
The untrained eye will find Steer's Head difficult to find. The plants are so extremely tiny and grow so close to the ground they are easily overlooked. In addition, they bloom only briefly, just after snow melts, at a time when most other plants are not flowering and the botanists are not out looking. The Yosemite Wildflower Guide (Yosemite National Park website) describes the difficulty of finding Steer's Head and suggests looking for the leaves rather than the flowers. Unfortunately, at our site Dwarf Waterleaf (Hydrophyllum capitatum) are abundant and when young have leaves similar to those of Steer's Head. This not only makes locating these plants difficult but also makes it easier to overlook the presence of Steer's Head altogether. For those reasons Steer's Head may actually be more abundant than its few records of occurrence in British Columbia would indicate.
Steer's Head is a choice rock garden plant, but is extremely difficult to grow outdoors west of the Cascades (Flora and Fauna Northwest website). Dicentra spp. are known to have toxic properties (Smolinske 1990) so grazing by animals may not be a threat. The American Apollo butterfly (Parnassius clodius) uses Steer's Head as its host plant and its larva are apparently immune to the Steer's Head poisons (Auckland et al. 2004) so other insects may also threaten this plant. Its small size, early-season growth behaviour, relatively deep root tuber and fairly wide distribution suggest the Steer's Head is well established and relatively safe from elimination.
[Editorial Note: I had three more items for this BEN issue, but I had some problems with my server and will have to send them later. Adolf Ceska
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