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Arnica (sororia)

Tara Luna
USDI NPS - Glacier National Park
West Glacier, Montana 59936
(406) 888-7835
http://plant-materials.nrcs.usda.gov/azpmc

Family Scientific Name: Asteraceae
Family Common Name: Sunflower family
Scientific Name: Arnica sororia Greene
Common Synonym: Arnica fulgens Pursh sororia
Common Name: Twin arnica
Species Code: ARNSOR
Ecotype: Many Glacier Valley
General Distribution: Twin arnica is a perennial species that ranges from southern British Columbia and Alberta south to California, Nevada, Utah and Wyoming. It ranges east to South Dakota. It is common on moist and shallow soils or on heavier loam soils in prairies.
Propagation Goal: plants
Propagation Method: seed
ProductType: Container (plug)
Stock Type: 160 ml (7.0 cu.in)
Time To Grow: 6 Months
Target Specifications: Root tight plug with multiple leaves.
Propagule Collection: Seeds are collected in early August. The fruits are achenes that are dark brown and 4 to 6 mm (0.15 to 0.23 in) long at maturity; with a pappus of white hairs at the apex. Seeds are usually mature by the end of July to early August and are quickly dispersed by wind.
Propagule Processing: Seeds must be collected as soon as the feathery pappus emerges from the seed heads. Achenes are collected in paper bags. Small collections can be cleaned by screening to remove the fluffy pappus from the achenes. Large collections can be cleaned by using an office clipper.There are approximately 990,000 seeds per kilogram (409,000 seeds per pound).
Seed Longevity:N/A
Germination Percent:65%
Pre-Planting Treatments: Inferred seed dormancy is non-deep physiological dormancy.

Seeds are cold, moist stratified for 60 days at 3ø C (37ø F). Seeds that have been dry stored for a few months may not require a stratification treatment, although a short cold moist treatment will likely improve germination uniformity.
Sowing Method: Direct Seeding.
Seeds are lightly covered with medium or mulch and kept evenly moist during germination.
Growing Area Preparation/
Annual Practices for Perennial Crops:
Seedlings are grown in a fully automated greenhouse. Greenhouse temperatures are set at 24ø C day/18ø C night (75/64ø F).
Seedlings are grown in Sunshine Mix #2 containing sphagnum peat and perlite with Osmocote controlled release fertilizer (13N:13P2O5:13K2O; 8 to 9 month release rate at 21C) and Micromax fertilizer (12%S, 0.1%B, 0.5%Cu, 12%Fe, 2.5%Mn, 0.05%Mo, 1%Zn) at the rate of 1 gram of Osmocote and 0.20 gram of Micromax per 172 ml conetainer.
Seedlings are handwatered as needed in the greenhouse. They are later moved to the outdoor growing area in early summer and irrigated with an automatic overhead sprinkler system.
Establishment Phase: Stratified seeds germinate 7 to 14 days after seeding under greenhouse temperatures of 24ø C day/18ø C night (75/64ø F).
Seedlings need to be kept evenly moist during germination and establishment.
Length of Establishment Phase: 2 to 4 weeks
Active Growth Phase: During active growth, seedlings need to dry down between irrigations. They are spaced as needed to increase airflow between containers.
Plants are fertilized with 20-20-20 liquid NPK at 100 ppm weekly during the growing season.
Length of Active Growth Phase: 2 months
Hardening Phase: Seedlings harden naturally during late summer and early fall in the outdoor nursery.<br> Twin arnica goes dormant in late summer. Growers must reduce irrigation during late summer and only water occasionally to keep root systems alive.
Length of Hardening Phase: 1 to 2 months
Harvesting, Storage and Shipping: Seedlings can be outplanted in fall or overwintered in the nursery under Microfoam sheets until early spring.
Length of Storage: 5 months
Other Comments: Twin arnica spreads vegetatively by long, slender rhizomes. It can be propagated by divisions.
References: Hitchcock CL, Cronquist A, Ownbey M, Thompson JW. 1971 (third printing). Flora of the Pacific Northwest. Part 5 Compositae. University of Washington Press. Seattle (WA) 343p. ISBN 0-295-73985-1

Citation:

Luna, Tara; Dedekam, Sara. 2008. Propagation protocol for production of Container (plug) Arnica sororia Greene plants 160 ml (7.0 cu.in); USDI NPS - Glacier National Park West Glacier, Montana. In: Native Plant Network. URL: https://NativePlantNetwork.org (accessed 2024/05/04). US Department of Agriculture, Forest Service, National Center for Reforestation, Nurseries, and Genetic Resources.