Fauna
Plant

Silver Beachweed

Ambrosia chamissonis

Also known as Silver Burr Ragweed, Beach Bur, Silver Beach Burr, Beach Burrweed

Silver beachweed anchors shifting coastal dunes with extensive sprawling runners, forming dense silvery mats that withstand salt spray and relentless onshore winds. Densely packed, woolly hairs cloak its foliage to reflect intense beach sunlight and trap humidity against arid coastal breezes. Wind carries its copious powdery pollen in summer, while spiny burr-like seed heads hook onto animal fur to hitch rides across maritime strands.

CoastalDune SpecialistDrought-Tolerant
Silver Beachweed reference
(c) Cody Hinchliff, some rights reserved (CC BY), uploaded by Cody Hinchliff · cc-by
—observations
—countries
—peak records
Least ConcernConservation statusIUCN Red List categoriesLCNTVUENCREWEXLeast ConcernRed List categories, explained →
Key facts
Diet & preyPhotosynthetic (sunlight, water, sandy soil nutrients)
Predators
  • Gall-forming flies
  • Coastal rodents
  • Black-tailed deer
ThreatsCoastal development, dune recreation, and invasive iceplant encroachment
HabitatsCoastal sand dunes, upper beach berms, and sandy maritime bluffs
Life spanPerennial (several years to over a decade)
Classification
  1. OrderAsterales
  2. FamilyAsteraceae
  3. GenusAmbrosia
  4. SpeciesAmbrosia chamissonis
Range & activity
Range data is not available yet.
Safe observation
Interaction riskLow
  1. Low
  2. Moderate
  3. High
  4. Very high
Why interaction risk is low
Produces windborne pollen that triggers severe seasonal allergies in sensitized individuals.
Why it is dangerous
Produces airborne ragweed pollen containing highly reactive proteins that trigger allergic rhinitis, conjunctivitis, and asthma flare-ups.
How to recognize a risky encounter
Look for low, sprawling beach mats of felted silver-gray leaves topped by upright spikes of tiny yellowish-green flower heads.
What to do
Avoid brushing against or walking through blooming stands if allergic to ragweed pollen.
Responsible observation
  • Pollen season: Sensitive individuals should keep distance during midsummer to late autumn bloom periods.
  • Footwear caution: Wear closed shoes near mature stands to avoid stepping on stiff, spiny seed burs.
  • Dune preservation: Stay on designated beach boardwalks to avoid damaging fragile, sand-binding roots.
Related species
Help improve the field guideSomething wrong?

Report a name, category, or profile issue for review.

Checking your Fauna account…