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Toxic to dogs. The ASPCA lists ranger's button as toxic to dogs. Ranger's button is a quantity plus sunlight plant. A dog that has grazed a patch and then lies in full sun is the case to describe carefully, watching ears, nose, belly and any pale or thin coated skin for a burn like reaction.
Ranger's button, also called white heads, is a tall wet meadow plant of western North American mountains and stream banks, topped with round white flower heads like small pompoms. The ASPCA lists Sphenosciadium capitellatum as toxic to dogs. Hikers meet it on trail edges beside creeks, exactly where a hot dog stops to drink and pushes through the vegetation.
The ASPCA names the toxic principle of ranger's button as Furanocoumarins. Ranger's button defends itself with furanocoumarins, light activated compounds in the carrot family. They do their damage in two steps: the plant material reaches the skin or the gut, and then sunlight switches the reaction on, producing the photosensitization the ASPCA lists, a sunburn like dermatitis on exposed skin. The ASPCA adds that large amounts are needed to cause this effect, and its White Heads entry for the same plant adds ocular toxicity to the picture.
The clinical signs the ASPCA lists for ranger's button are: photosensitization (sunburn and dermatitis), with ocular toxicity listed on the ASPCA's White Heads entry for the same plant; large amounts are needed to cause the effect. The exposure is a trail exposure. A dog works through a stand of ranger's button at a creek crossing, mouths the heads, gets sap and plant juice on its muzzle and coat, and then spends the afternoon in high altitude sun. The reaction, when it comes, looks like an odd sunburn: red, sore, weeping skin on the nose, ear edges and other exposed places, sometimes with sore eyes. Owners rarely connect a skin case to a plant met two days earlier on a hike, which is why the grazing and sunlight history is worth telling the veterinarian in full.
Most dangerous part: The flowering heads and foliage of a plant a dog pushes through or grazes in quantity on a bright day. Casual contact with a single plant is not the pattern behind the listing.
Ranger's button sits in the carrot family, Apiaceae, the family with the most dangerous lookalike problem in this database: poison hemlock and water hemlock grow in the same wet places. Never let a trail identification rest on white flowers alone. If a dog has grazed a white flowered umbel plant by water and shows any sign beyond skin soreness, treat the identification as open and call at once, because the hemlocks are a different and far worse conversation.
Call your veterinarian, the ASPCA Animal Poison Control Center on (888) 426-4435, or the Pet Poison Helpline on (855) 764-7661 right away, even if your dog looks fine. Some poisons take hours or days to show their worst effects. Do not make your dog vomit unless a veterinarian tells you to, and keep the packaging, a photo, or a sample of what was eaten to show the clinic.
Keep dogs on the trail tread through wet meadow stands rather than letting them push through tall umbel plants at creek crossings, and rinse plant juice off the coat after a hike through dense growth. Learn the plant's round white heads before hiking its range, and photograph stands you are unsure of instead of letting the dog sample them.
No substitute applies to a wild plant. For a planted wet corner at home, verify any candidate on the ASPCA list by scientific name first; Sphenosciadium is a trail plant to walk past, not to import. Whatever you plant next, check it on the toxic plants index approach: confirm the plant on the ASPCA toxic and non-toxic list under its scientific name, Sphenosciadium capitellatum is the name to avoid here, before it goes in the ground or on the shelf.
Yes. The ASPCA lists ranger's button (Sphenosciadium capitellatum) as toxic to dogs. Its toxic principle is Furanocoumarins, and the signs it lists include photosensitization (sunburn and dermatitis), with ocular toxicity listed on the ASPCA's White Heads entry for the same plant; large amounts are needed to cause the effect.
Call your veterinarian, the ASPCA Animal Poison Control Center on (888) 426-4435, or the Pet Poison Helpline on (855) 764-7661 straight away. Note what part of the plant was eaten and roughly how much, keep any remaining plant material to show the clinic, and do not make your dog vomit unless a veterinarian tells you to.
The flowering heads and foliage of a plant a dog pushes through or grazes in quantity on a bright day. Casual contact with a single plant is not the pattern behind the listing.
Its furanocoumarins are light activated. Plant material on skin or in the gut plus strong sun produces the burn like dermatitis the ASPCA lists, which is why the same grazing on a dull day may cause nothing visible.
It could, and that possibility is exactly why white flowered carrot family plants by water should never be identified by flower color alone. If there is any doubt about the plant, call a poison line and describe the site and the plant in detail.
This page is general information drawn from the published guidance of the organizations listed under Sources below. It is not veterinary advice, and it does not replace your own veterinarian, who knows your dog. If your dog has eaten something toxic, contact your veterinarian, the ASPCA Animal Poison Control Center on (888) 426-4435, or the Pet Poison Helpline on (855) 764-7661 straight away. A consultation fee may apply on the helplines.
Last updated: November 2026. Every verdict on this page was checked against the sources listed above. How we work: our methodology.
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