Prickly Lettuce (Lactuca serriola)
Updated October 16th, 2025An annual native to Europe, Asia, and North Africa, introduced to North America where it is often considered invasive.
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An annual native to Europe, Asia, and North Africa, introduced to North America where it is often considered invasive.
Horseweed is an annual plant, native to North America and widely distributed across the continent. It has been introduced to temperate zones in Asia, Europe, and Australia. It is a frequent weed in agricultural lands, especially in no-till agriculture.
A small annual with distinctive coral-red flowers, native to Europe, western Asia and North Africa, and introduced in North America.
A hilly region central along the Alberta-British Columbia border, east of the Canadian Rockies, covered in boreal forest.
A region in Oklahoma and slightly into Kansas, with varied topography, soils, and vegetation cover.
These two species are closely-related, visually similar, and occupy similar habitats. They can usually be distinguished by closely examining their stems, growth habit, and lower leaves, and they have a few other subtle differences. S. curtisii is restricted to the Southern Appalachians, prefers moister conditions, and tolerates greater shade. S. caesia has a much broader range, is more common at lower elevations, and ranges into sunnier, drier conditions.
These two goldenrods are frequently confused in their small range of overlap. Both bloom early, have smooth leaves, upper leaves that lack serrations, and grow in dry habitats, often those with sandy, acidic soil. They are easily distinguished by inflorescence shape, floret count per flowerhead, leaf bases, and serrations on lower leaves. S. juncea ranges farther north, prefers more nutrient-rich, less-acidic soil, and is more likely in anthropogenic or human-disturbed habitats. S. odora ranges farther south and is strictly limited to sites with acidic, nutrient-poor soils, but less likely on sites disturbed or altered by humans.
These two goldenrods are sometimes confused; both tend to grow in dry habitats. They are usually easy to tell apart by close examination of the leaves, and they have numerous other differences. S. altissima ranges farther north and much farther west, and prefers richer, finer-textured soils, ranges onto higher-pH soils, and tolerates much greater levels of disturbance. S. odora is more restricted to the southeast and is strictly limited to acidic, nutrient-poor soils, and is more shade-tolerant, but less tolerant of disturbance.