Beggar’s Lice is a common name applied to plants whose seeds stick tenaciously to clothing and animal fur, but this single name actually refers to species from at least two different plant genera. The primary concern for people encountering these plants is often whether they are chemically toxic or poisonous if accidentally ingested. The most common varieties of beggar’s lice, such as those in the Desmodium and Hackelia genera, are generally considered non-toxic to humans and pets in small amounts. While they do not pose a serious chemical threat, the plants present other hazards, primarily related to their sticky seed pods, which can cause significant physical discomfort and irritation.
Identifying the Common Varieties of Beggar’s Lice
The two major plant groups sharing the name “beggar’s lice” belong to different botanical families and have distinct appearances. One group is the Desmodium genus, often called tick-trefoil, which is part of the Fabaceae, or pea family. These are typically herbaceous perennials or subshrubs with trifoliate leaves, meaning each leaf stalk bears three leaflets. Desmodium species produce small flowers that are commonly pink or mauve and develop into narrow, segmented seed pods called loments.
The second major group is the Hackelia genus, known as stickseeds, which belongs to the Boraginaceae, or borage family. These plants are often biennial, forming a rosette of leaves in their first year before producing a taller stem and flowers in the second year. Hackelia species generally have flowers that are blue or white, and their common name, stickseed, directly references the tendency of their barbed nutlets to cling to fur and fabric. Proper identification is important because some toxic weeds may look similar and often grow nearby.
Chemical Toxicity: The Verdict on Ingestion
The most common Desmodium and Hackelia species are not known to contain potent toxins that cause severe poisoning in humans or domestic animals. When small amounts of the foliage or seeds are accidentally ingested, the effect is typically mild, possibly resulting in minor stomach upset or temporary vomiting. This reaction is usually the body’s natural response to unfamiliar plant matter rather than a sign of true chemical poisoning.
However, caution is warranted because of the possibility of misidentification with genuinely dangerous plants that share similar habitats or appearances. For instance, young cocklebur plants and their seeds are poisonous, and this plant is often encountered alongside beggar’s lice. Furthermore, other toxic weeds, including those from the nightshade family (Solanaceae), which contain various psychoactive and lethal alkaloids, might be mistaken for a harmless plant if a person is not certain of the identity. Proper identification is paramount to ensure safety, as even a small quantity of a truly poisonous look-alike can be harmful.
Physical Irritation and Mechanical Risks
The most frequent and noticeable hazard posed by beggar’s lice is mechanical, stemming from the structure of the burrs themselves. The seed pods of both Desmodium and Hackelia are covered in numerous microscopic, hooked hairs called uncinate trichomes. These tiny hooks act like Velcro, allowing the seed to cling tightly to anything fibrous, which is a highly effective dispersal method.
The burrs pose a particular risk to pets, as they can quickly become deeply matted in an animal’s fur, especially in long-haired breeds. If the burrs are not removed promptly, they can work their way between paw pads or into the crevices between toes, causing irritation and potential ulcerations. For humans, contact can cause skin irritation, and if a person handles the seeds and then rubs their eyes, the burrs can cause significant eye discomfort. The safest way to remove the burrs from clothing is typically to use a stiff brush or a coarse object, and for pet fur, a brush or comb can be used to pull them out, sometimes requiring a quick trim if they are too tangled.