BC Conservation Data Centre: Species Summary
Tonella tenella
small-flowered tonella
| Scientific Name: | Tonella tenella (Benth.) Heller | ||||||||||
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| English Name: | small-flowered tonella | ||||||||||
| Classification / Taxonomy | |||||||||||
| Scientific Name - Concept Reference: | Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR. | ||||||||||
| Classification Level: | Species | ||||||||||
| Species Group: | Vascular Plant | ||||||||||
| Species Code: | TONETEN | ||||||||||
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| Conservation Status / Legal Designation | |||||||||||
| Global Status: | G4 (Mar 2025) | ||||||||||
| Provincial Status: | S3 (Apr 2019) | ||||||||||
| BC List: | Blue | ||||||||||
| Provincial FRPA list: | |||||||||||
| Provincial Wildlife Act: | |||||||||||
| COSEWIC Status: | Endangered (Nov 2003) | ||||||||||
| SARA Schedule: | 1 - Endangered (Jul 2005) | ||||||||||
| General Status Canada: | 1 - At Risk (2010) | ||||||||||
| Ecology & Life History | |||||||||||
| General Description: | |||||||||||
| Technical Description: | |||||||||||
| Identification Comments: | Tonella tenella is a slender, ascending to sprawling, annual herb from a delicate taproot (Pojar 2000). Stems smooth, often branched, 5-25 cm tall. Leaves are opposite, smooth or soft-hairy on the upper surface. The lowermost leaves are stalked, ovate to round, 1-2 cm long and few-toothed. The middle and upper leaves become sessile upward and deeply 3-lobed with the segments progressively narrowing upward. The uppermost leaves are reduced and often entire. The inflorescence consists of one to several long-stalked flowers in the axils of the bracts, with smooth or minutely glandular-hairy stalks. The corollas are blue and white, short-tubular, 2-4 mm wide, and 2-lipped with the upper lip 2-lobed, the lower lip 3-lobed, and the middle lobe the largest. The calyces are up to 3 mm long, and deeply 5-lobed with the lobes longer than the tube. The 4 stamens are exserted and the fruits are ovate to globe-shaped capsules. The 2 to 4 seeds are large, 1-1.5 mm long and wingless. | ||||||||||
| Similar Species: | Collinisia parviflora is a similar small annual with two-lipped blue flowers that occurs in the same habitat as Tonella. It differs from Tonella in having the upper lip of the flower reflexed and the lower lip saccate, with the middle of three lobes on the lower lip being the smallest. The upper lip of Tonella is hardly reflexed, the lower lip is not saccate, and the middle lobe of the lower lip is the largest. Leaves along the central part of the stem are simple, linear to narrowly elliptical in Collinsia, but in Tonella they are three-lobed, with the lobes linear or narrowly elliptical. | ||||||||||
| Provincial Reproduction Comments: | Tonella is self-compatible and self-pollination occurs early, but outcrossing is also possible. A number of floral charcteristics have been described for Tonella by Armbruster et al. (2002): stigmas are receptive to pollen-tube growth early in Tonella species, 'small-flowered types" like Tonella tenella do not maintain spatial separation of anthers and stigmas early in anthesis by differential elongation of staminal filaments, and anther-stigma contact and self-pollination occur early. Low elevation pollinators probably include a variety of bees including Bombus, Anthophora, Emphoropsis, Synhalonia and Osmia (Armbruster et al. 2002). | ||||||||||
| Provincial Ecology Comments: | Historically, the habitat of Tonella tenella was maintained by aboriginal burning practices, probably on an annual basis, although talus slopes sometimes were refugia from fires because fuel loads were not great enough to carry a fire into the rocky areas. In the absence of burning, invading woody plants and exotic grasses and herbs may be shading out T. tenella, competing for resources, or may prevent the recruitment of seedlings necessary for the maintenance of these populations. | ||||||||||
| Habitats: (Type / Subtype / Dependence) |
Forest / Conifer Forest - Dry / Facultative - frequent use
Forest / Garry Oak Woodland / Facultative - frequent use Other Unique Habitats / Vernal Pools/Seasonal Seeps / Obligate Rock/Sparsely Vegetated Rock / Rock/Sparsely Vegetated Rock / Facultative - frequent use Rock/Sparsely Vegetated Rock / Talus / Facultative - frequent use |
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| Global Habitat Comments: | Tonella tenella occurs in "moist, shaded canyons, moist open coniferous and deciduous forests, [and] talus slopes" (FNA 2019). In California, this species is found in chaparral, oak, and mixed woodland communities (Jepson Flora Project 2025). | ||||||||||
| Provincial Habitat Comments: | Tonella tenella occurs on west-facing slopes on thin soils over gravelly rock outcrops or stable talus. At the single known locality on Saltspring Island, it occurs in a narrow band extending up the mountainside for approximately 425 m (Douglas and Penny 2003). The talus slope occurs in open Acer macrophyllum - Arbutus menziesii - Quercus garryana forest in the dry coastal Douglas-fir zone. Associated species include Galium aparine, Cardamine oligosperma, Claytonia perfoliata, Bromus sterilis, Collinsia grandiflora, Melica harfordii, and Torilis japonica. Conspicuous mosses include Eurhynchium oreganum and Dicranum species. | ||||||||||
| Provincial Phenology: (1st half of month/ 2nd half of month) |
Jan: Vegetative / Vegetative
Feb: Vegetative / Vegetative Mar: Vegetative / Vegetative Apr: Vegetative / Vegetative, Flowering May: Flowering / Flowering Jun: Flowering, Fruiting / Fruiting Jul: Fruiting / Fruiting Aug: Fruiting / Fruiting Nov: Germinating / Germinating Dec: Germinating / Germinating |
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| Provincial Phenology Comments: | Phenological studies are not available for BC, but the pattern is probably the same as in populations further south, and typical of vernally-flowering species in dry environments that must have a rapid life cycle. Seeds germinate after fall rains commence, shoot development occurs in late winter, flowering in April to June, seed dispersal begins by early to midsummer, and then plants senesce with summer drought. | ||||||||||
| Elevation (m) (min / max): | Provincial: 0 / 600 | ||||||||||
| Known Pests: | |||||||||||
| Pollen Vector: | |||||||||||
| Pollinator: | |||||||||||
| Dispersal: | |||||||||||
| Provincial Inventory | |||||||||||
| Inventory Priority: | B - Strong | ||||||||||
| Ownership of occurrences (Known locations): | Mostly private | ||||||||||
| Inventory Need: | More sites on both the Gulf Islands and southeastern Vancouver Island need to be searched for this species. The last inventory was done in 2002. Searches have been made in other potential habitats on Salt Spring Island as well as on Vancouver Island, but because Tonella tenella is so small and difficult to detect, it is quite likely that other subpopulations remain undetected. Searches need to be made in spring and early summer before plants dry up and die in summer drought. | ||||||||||
| Inventory Comments: | None. | ||||||||||
| Economic Attributes | |||||||||||
| Provincial Economic Comments: | No commercial or traditional uses are known for this species. | ||||||||||
| Distribution | |||||||||||
| Endemic: | N | ||||||||||
| Global Range Comment: | Tonella tenella occurs in western North America, from British Columbia, Canada south through Washington, Oregon, and California in the United States (FNA 2019). Range extent was estimated using herbarium specimens, photo-based observations, and NatureServe Network occurrence data collected between 1994 and 2025 (RARECAT 2024, GBIF 2025, iNaturalist 2025, NatureServe 2025, SEINet 2025). | ||||||||||
| Disjunct, more common elsewhere: | Y | ||||||||||
| Peripheral, major distribution elsewhere: | Y | ||||||||||
| Authors / Contributors | |||||||||||
| Global Information Author: | N. Ventrella (2025) | ||||||||||
| Last Updated: | Mar 31, 2025 | ||||||||||
| Provincial Information Author: | Christy, J.A. | ||||||||||
| Last Updated: | Feb 22, 2005 | ||||||||||
| Last Literature Search: | |||||||||||
| References and Related Literature | |||||||||||
Armbruster, W.S., et al. 2002. Comparative analysis of late floral development and mating-system evolution in tribe Collinsieae (Scrophulariaceae s.l.). Am. J. Bot. 89:37-49. |
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B.C. Ministry of Environment. Recovery Planning in BC. B.C. Minist. Environ. Victoria, BC. |
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COSEWIC. 2003v. COSEWIC assessment and status report on the small-flowered tonella Tonella tenella in Canada. Comm. on the Status of Endangered Wildl. in Can. Ottawa. vii + 14 pp. |
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Douglas, G.W. and J.L. Penny. 2003c. COSEWIC status report on the small-flowered tonella Tonella tenella in Canada in COSEWIC assessment and status report on the small-flowered tonella Tonella tenella in Canada. Comm. on the Status of Endangered Wildl. in Canada. Ottawa. 1- 14 pp. |
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Douglas, G.W., D. Meidinger, and J. Penny. 2002. Rare Native Vascular Plants of British Columbia, 2nd ed. B.C. Conserv. Data Centre, Terrestrial Inf. Branch, Victoria. 358pp. |
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Douglas, G.W., D. Meidinger, and J. Pojar, eds. 2000. Illustrated Flora of British Columbia, Vol. 5, Dicotyledons (Salicaceae through Zygophyllaceae) and Pteridophytes. B.C. Minist. Environ., Lands and Parks, and B.C. Minist. For., Victoria. 389pp. |
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Flora of North America Editorial Committee (FNA). 2019. Flora of North America north of Mexico. Vol. 17: Magnoliophyta: Tetrachondraceae to Orobanchaceae. Oxford Univ. Press, New York. xxiv + 737 pp. |
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Jepson Flora Project (eds.) 2025. Jepson eFlora. Online. Available: https://ucjeps.berkeley.edu/eflora/ (accessed 2025). |
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Maslovat, C. 2009. Guidelines for Translocation of Plant Species at Risk in British Columbia. B.C. Minist. of Environ. Victoria, BC. |
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Pojar, J. 2000. Scrophulariaceae. Pp. 114-218 in G.W. Douglas, D. Meidinger, and J. Pojar, eds. Illustrated Flora of British Columbia, Vol. 5, Dicotyledons (Salicaceae through Zygophyllaceae) and Pteridophytes. B.C. Minist. Environ., Lands and Parks, and B.C. Minist. For., Victoria, BC. 427pp. |
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Please visit the website Conservation Status Ranks for definitions of the data fields used in this summary report.
Suggested Citation:
B.C. Conservation Data Centre. 2025. Species Summary: Tonella tenella. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jun 6, 2026).