Introduction to the Tofieldiaceae Family

The Tofieldiaceae family is a very small, mostly northern family of bogs and fens, some of my favorite habitats to explore. They are considered a basal monocot, diverging early in evolution, giving them some unique features.

I have only found Triantha glutinosa in this family several times, but it has always been found in a bog or fen at medium to high elevation in the mountains of coastal British Columbia. So, of course, I immediately was drawn to them.

Common Botanical Description

If you’re new to plant morphology, this guide is a perfect beginner’s description, with no need to know any scientific jargon. Below this section is additional information on uses and morphology photos to help you identify the family, followed by pictures of individual species found in North America. But for researchers or those wanting to learn a more in-depth version, refer to the Scientific Botanical Description below the images for highly detailed scientific descriptions and genus-level distribution data.

Leaves and Stems of the Tofieldiaceae: This family is made of mostly small perennial herbs with flat, odorless leaves that lack a distinctive upper and lower surface. They are simple (not compound), appearing somewhat grass-like in appearance, or, rarely, egg-shaped, and have parallel veins.

Flowers of the Tofieldiaceae: Flowers mostly contain both male (stamens) and female (ovary, style, stigma) parts in the same flower (bisexual) and have nectaries. Inflorescences usually come from leafless stalks and are arranged in loose or contracted spikes. There is usually a conspicuous whorl of 3 bracts (calyculus) located just below the flowers, which helps identify the family. Flowers are made of 2 whorls of greenish or petal-like tepals in white, cream, purple, or brown.

Reproductive Features of the Tofieldiaceae: There are usually 2 whorls of stamens (3+3), but there may be more in Pleea. The ovary is variable but always with 3 chambers (carpels) with 1 or 3 free terminal styles, each with a stigma.

Fruits of the Tofieldiaceae: The fruits are mostly dry capsules, and the seeds usually have distinct terminal appendages.

Uses of Tofieldiaceae 

This is a small family of mostly wild, not invasive, non-cultivated plants, but Tofieldia pusilla is sometimes grown as an ornamental plant.

Ecological & Wildlife Values of Tofieldiaceae

The Tofieldiaceae family is an important component of bogs, fens, marshes, and other wet, swampy areas where they provide critical habitat and nectar for bog-dwelling insects, amphibians, and reptiles. Some are even carnivorous and trap flies in sticky sap to derive nutrients in nutrient-poor ecosystems where many plants cannot survive.

Morphology of Tofieldiaceae in North America

Some Species of Tofieldiaceae Found in North America

Triantha glutinosa—Sticky False Asphodel

Herbaceous perennial, 5–50 cm tall, with leaf blades up to 30 cm long. Inflorescences are 3-30-flowered and spike-like but may be interrupted or open and have bracts subtending the flower stalks. Flowers are yellowish-white with 6 tepals. It often has sticky glands below its inflorescence, which makes it a protocarnivorous plant since it uses them to trap flies to gain nutrients in nutrient-poor bogs or fens. It is native to northern North America, mostly Canada and Alaska but south to Virginia in the eastern USA. This one was in the mountains on the Sunshine Coast of BC, Canada.

Scientific Botanical Description of the Tofieldiaceae Family

Habit & Leaf Form of the Tofieldiaceae Family

The Tofieldiaceae family are mostly small perennial, rarely annual, herbs that are autotrophic or rarely parasitic mycoheterotrophic but always green and photosynthesizing. Leaves are well-developed and may or may not have a basal aggregation of leaves. They are mostly rhizomatous, but may be tuberous or, rarely, from corms. Leaves are arranged alternately along the stem, usually spirally but sometimes distichously.

Leaves are flat and herbaceous, usually sessile but may be almost petiolate at times. They are two-ranked, isobifacial, borne edgewise to the stem, and are odorless. They are simple with entire margins, usually lanceolate, but sometimes linear or rarely ovate, always with parallel veins. Leaves are only ligulate in Pleea. The mesophyll often contains crystals.

Flowers of the Tofieldiaceae Family

Plants are almost always hermaphrodites but rarely may be dioecious or polygamomonoecious. Floral nectaries are always present with secretion from the gynoecium except in Tofieldia, which has septal nectaries. Inflorescences are +/- scapiflorous, arranged in spikes, racemes, or corymbose cymes, with inflorescence bracts. Flowers are often bracteate, with a calyculus (whorl of 3 bracts) located just below the sepals (sometimes absent in Tofieldia), which is a useful diagnostic for the family.

Flowers are almost always actinomorphic, 3-merous, and pentacyclic. Perigone tube present to absent. Hypogynous disk absent. The perianth is made of 6 free to joined tepals that may be spreading, distinct, or shortly basally connate. They are 2-whorled (3+3), isomerous, sepaloid or petaloid, similar in the two whorls, and may sometimes be spotted. The tepals may be green to white, cream, purple, or brown but are usually inconspicuous and lack spurs or obvious patterns.

Some Triantha members are carnivorous via sticky hairs in their inflorescences that trap flies.

Androecium of the Tofieldiaceae Family

There are usually 6 androecial members (9 or 12 in Pleea). They are usually diplostemonous, with all fertile stamens more or less free of the perianth and free of one another; they are normally alterniperianth. They are usually 2-whorled 3+3 but may be 2-whorled 6+3 or 6+6 in Pleea. Stamens are filantherous and sometimes flattened. Anthers are dorsifixed (hypopeltate) or basifixed; versatile; dehiscing via longitudinal slits; and introrse.

Gynoecium of the Tofieldiaceae Family

The gynoecium is 3-carpeled, semicarpous (carpels are free above, and in Isidrogalvia (now included in Harperocallis), they are free almost to their bases), synovarious (with separate styles), or syncarpous (some Tofieldia are 3-locular with one style and a capitate stigma); it is isomerous with the perianth. The ovary is superior or partly inferior. Carpels (or locules) have 5 to many ovules with marginal or axile (when syncarpous) placentation. Terminal styles 1 or 3; always free when there are 3. Stigmas 1 or 3. Ovules are funicled, non-arillate, usually anatropous, bitegmic, and crassinucellate. 

Fruit of the Tofieldiaceae Family

The fruits are always non-fleshy and are usually a dehiscent septicidal capsule or follicle but may be an aggregate. Seeds are endospermic and oily, usually winged or with terminal appendages. Testa without phytomelan (by contrast with most capsular Asparagales, also lacking phlobaphene).

Taxonomy of Tofieldiaceae

The Tofieldiaceae is a small family of just 31 species in 3–5 genera (generic delineations are still uncertain) within the Alismatales order of the basal monocot clade. Molecular phylogenetic studies have shown it to be the second diverging clade in Alismatales after the Araceae.

Prior to molecular phylogenetics, its genera had usually been assigned to Nartheciaceae, Liliaceae, or Melanthiaceae. Pleea is also sometimes included in the Melanthiaceae, but here we place it in Tofieldiaceae as per APG IV.

Genera of the Tofieldiaceae Family:

Harperocallis (11), Pleea (1), Tofieldia (13), Triantha (4)

Key Differences From Similar Families

The Melanthiaceae family is the most likely to be confused with the Tofieldiaceae, and until modern molecular phylogenetics determined it to be a separate family, it was often included in the Melanthiaceae. However, they can be distinguished by the smaller size of Tofieldiaceae, primarily subarctic bog and fen habitats, and carpels that are distinct, each with their own separate style compared to larger perennials more often in woodlands and carpels that are typically fused. Also, none of the Melianthiaceae family members possess a calyculus, unlike most members of the Tofieldiaceae family.

Distribution of Tofieldiaceae

The Tofieldiaceae family can be found from frigid arctic and subarctic zones to temperate and even tropical, but most are northern temperate, arctic, and subarctic in North America and northern Europe and Asia.

Distribution of Tofieldiaceae in the Americas

Canadian Genera Include:

Tofieldia  2 spp. native in all of Canada, including the Arctic (and Greenland) but excluding NB, NS, and PE; Triantha 2 spp. native in all of Canada inc Arctic but exc PE.

USA Genera Include:

Harperocallis 1 endemic native of W FL; Pleea 1 monospecific southeast US endemic native to AL, FL, SC, and NC; Tofieldia 3-6 spp native to MT, MN, MI, SC, NC, and AK; Triantha 3 spp native to WA, OR, CA, ID, MT, WY, ND, MN, WI, IL, IN, OH, MI, NY, CT, VT, NH, ME, WV, VA, MD, DE, NC, SC, TN, TX, LA, MS, AL, GA, and FL.

Mexico Genera Include:

Absent

Neotropical Genera Include:

Harperocallis 10 spp., mostly narrow endemics, found in Venezuela, Bolivia, Colombia, Brazil, Ecuador, and Peru.

Patagonia Genera Include:

Absent

Additional Information and References

• Visit Lyrae’s Dictionary of Botanical Terms to learn the terminology of botanists. Note that if you hover over most of the words in the articles, you can also get definitions from them there.
• Willis, Lyrae (Unpublished). Plant Families of North America. This is where all of the family descriptions come from. Below should be most of my references for this, along with my own personal observations throughout North America.
• Canadensys: Acadia University, Université de Montréal Biodiversity Centre, University of Toronto Mississauga, University of British Columbia. http://data.canadensys.net/explorer (accessed 2020 – current)
• FNA (1993+). Flora of North America. https://floranorthamerica.org/Main_Page. Accessed 2022-current.
• GBIF.org (2020+), GBIF Home Page. Available from: https://www.gbif.org
• iNaturalist.org (2020+). https://www.inaturalist.org/. Accessed 2020-current.
• Naturalista: CONABIO http://www.naturalista.mx (Accessed 2020–current).
• Neotropikey: Milliken, W., Klitgård, B., & Baracat, A. eds. (2009+). Neotropikey: Interactive key and information resources for flowering plants of the Neotropics. www.kew.org/neotropikey.com (accessed 2020 – current).
• Patagonia Wildflowers: Wildflower Identification Site. https://patagoniawildflowers.org/ Accessed throughout the fall of 2020.
• POWO (2019+). Plants of the World Online. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet: http://www.plantsoftheworldonline.org/
• Stevens, P. F. (2001+). Angiosperm Phylogeny Website. Version 14, July 2017 [more or less continuously updated since]. http://www.mobot.org/MOBOT/research/APweb/
• USDA, NRCS. 2020. The PLANTS Database (http://plants.usda.gov, 2 June 2020). National Plant Data Team, Greensboro, NC, USA; Accessed 2020-present.
• Watson, L., and Dallwitz, M.J. (1992+). The Families of Flowering Plants: descriptions, illustrations, identification, and information retrieval. Version: 2nd May 2020. delta-intkey.com. Accessed spring through fall of 2020.
• WFO (2022): World Flora Online. Published on the Internet: http://www.worldfloraonline.org. Accessed Spring 2022 – current

My Current Plant Family Education Fundraiser

I am currently seeking funding to expand my website and SEO capabilities as I keep adding new families, and I am also looking to invest in a new macro lens, as I will soon be adding floral dissections to the families as they become available to me. You can donate to help support native plant education using the GoFundMe link, also at the bottom of the page.

Copyright Information

The information and the photos on this site are free to use for educational purposes, with proper attribution. For other uses, please contact me first.

You can cite this site as follows: Willis, Lyrae (2020+). Lyrae’s Nature Blog – Plant Families of North America. https://lyraenatureblog.com/. Accessed [DATE].