Californian bur is a coarse annual weed in the daisy family whose hooked, spiny burs hitch rides on animal fur and clothing. It is native to North America and has spread as a weed to many parts of the world. In the US it is often lumped in with common cocklebur (Xanthium strumarium), and botanists still disagree on how to divide this group.
Appearance
- Growth form
- An upright, usually branched annual up to about 6.5 ft (2 m) tall, with rough green or purplish stems.
- Leaves
- Broad, triangular to oval leaves 1.5–6 in (4–15 cm) long with 3 to 5 lobes, a heart-shaped base, and coarse teeth; rough on both sides.
- Flowers
- Small male flower heads cluster at the top of the stems; female heads sit in the leaf axils below.
- Fruit
- Oval burs about 0.6–1 in (1.5–2.5 cm) long, covered in hooked spines and topped by two stout, inward-curving beaks. Each bur holds two seeds of different sizes.
Look-alikes
Common cockleburXanthium strumarium
The two are very similar, and many US references lump them together, so photos alone often can't separate them. Californian bur tends to be the bigger, coarser plant; a close look at the bur is the best check.
Why they get mixed upMany US guides treat both under the name common cocklebur.
Where it lives
- Typical habitats
- Roadsides
- Vacant lots
- Seashores
- Range
- Native to North America, where it grows across much of the US; naturalized in Europe, East Asia, and Australia.
Life cycle
- Seed dispersal
- The hooked spines catch in fur and clothing.
Cautions
- Cautions
- Cocklebur seeds and young seedlings contain a potent toxin. Livestock—especially pigs—can die after eating seedlings at the two-leaf stage.
Name and classification
- About the name
- Xanthium orientale, X. strumarium, X. occidentale, X. italicum, and X. cavanillesii are often treated as one variable aggregate. Plants in this group can hybridize, so names vary between references. Older names include X. canadense and X. strumarium var. canadense.
Culture and stories
- Culture and stories
- The Zuni people used a poultice of the seeds to draw out splinters and ground the seeds with cornmeal to make steamed cakes.
More species to explore
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