Is Sea Lettuce Tree Edible? Separating a Toxic Tree from Edible Seaweed

November 1, 2025 •

3 min read

The common name 'sea lettuce' causes significant confusion because it refers to two completely different organisms: the edible seaweed (Ulva lactuca) and the potentially toxic tree (Pisonia grandis). Clarifying if the sea lettuce tree is edible is a matter of botanical identification and serious safety concerns, as they are not interchangeable.

Quick Summary

The 'sea lettuce tree' (Pisonia grandis) is a tropical plant known for its toxic compounds and bird-trapping seeds, making it unsafe for human consumption. It should not be confused with the edible marine algae, Ulva lactuca, commonly known as sea lettuce.

Key Points

Not Edible: The plant commonly called the 'sea lettuce tree' (Pisonia grandis) is not safe for consumption and should not be eaten.
Different Organisms: Do not confuse the tree with the edible marine algae also named 'sea lettuce' (Ulva lactuca).
Contains Toxins: The Pisonia grandis tree has been reported to contain toxic compounds and can cause illness if ingested.
Bird-Catcher Threat: The tree's sticky seeds pose a threat to small birds and wildlife, trapping and immobilizing them.
Foraging Confusion: The shared name is a dangerous botanical mix-up that highlights the critical need for positive identification before consuming wild plants.
Avoidance is Key: Due to conflicting reports and confirmed toxicity, the safest course of action is to avoid consuming any part of the Pisonia grandis tree.

The query 'is sea lettuce tree edible?' highlights a critical point of confusion for foragers and home cooks. The simple answer is no—at least not the tree. This common name applies to two entirely distinct species: a marine algae and a terrestrial tree. Consuming the wrong one can have severe consequences, ranging from illness to poisoning. This guide clarifies the difference between the two and provides crucial safety information.

The Crucial Distinction: Seaweed vs. Tree

The most important step is to understand the origin of the plant. If you are on the coast and find a green, leafy alga clinging to rocks, you have likely found the edible seaweed, Ulva lactuca. If you are looking at a large, brittle-branched tree with long leaves, particularly in a tropical or coastal setting, you have encountered the dangerous Pisonia grandis.

The Edible Sea Lettuce (Ulva lactuca)

This is a familiar and widely consumed green seaweed. It is identifiable by its ruffled, translucent, paper-thin fronds that resemble lettuce leaves.

Habitat: Grows in shallow coastal waters attached to rocks or floating freely.
Culinary Uses: Eaten raw in salads, dried and used as a seasoning, added to soups, or incorporated into dishes like Welsh laver bread.
Harvesting Safely: It is critical to harvest from clean, unpolluted waters, away from industrial outflows, as seaweed can absorb heavy metals. Avoid consuming it during or after periods of red tide contamination.

The Contested Sea Lettuce Tree (Pisonia grandis)

Also known as the "bird-catcher tree" or "birdlime tree," this is a soft-wooded, brittle tree found on tropical islands. Its leaves have been historically used as a vegetable in certain regions, but its edibility is highly disputed and the plant is widely considered toxic.

Habitat: Found in tropical regions of the Indian and Pacific Oceans.
Identifying Danger: The tree produces flowers that develop into long, cylindrical fruits with sticky prickles. These seeds are notorious for trapping and killing small birds, hence its ominous nickname.
Toxicity: Reports exist of adverse health effects, including vomiting and abdominal pain, after consuming the leaves. More definitive warnings confirm it is toxic to both pets and humans.

Comparison: Edible Seaweed vs. Toxic Tree

To ensure you do not make a dangerous mistake, this table highlights the key differences between the two species:


Feature	Edible Sea Lettuce (Ulva lactuca)	Sea Lettuce Tree (Pisonia grandis)
Scientific Name	Ulva lactuca	Pisonia grandis
Common Names	Green Laver, Aosa	Bird-catcher Tree, Birdlime Tree, Cabbage Tree
Classification	Green Marine Algae (Seaweed)	Tree, related to Bougainvillea
Environment	Shallow coastal waters, intertidal zones	Tropical islands, coastal areas
Edibility	Edible when properly sourced and prepared	Highly Contested & Potentially Toxic
Key Safety Concern	Water contamination, toxic decomposition	Sticky bird-trapping seeds, internal toxicity

Why You Must Avoid Consuming the Sea Lettuce Tree

The risks associated with ingesting Pisonia grandis far outweigh any perceived benefits. Trusting outdated or conflicting information on its edibility is a dangerous gamble.

Poisonous Compounds: Botanical sources and toxicology reports indicate the presence of potentially harmful chemicals in the plant's leaves and other parts.
Animal Harm: The name "bird-catcher tree" is a stark warning. The sticky fruits are a known danger to local wildlife, and this danger is a strong indicator of the tree's overall toxic nature.
Inconsistent Information: The conflicting reports on edibility suggest that traditional knowledge may be limited to specific preparations or cultivars, or could be erroneous. Lacking definitive safety protocols, avoidance is the only responsible course of action.
Identification Errors: Mistaking a toxic tree for edible seaweed is a classic foraging hazard. The shared common name is a perfect storm for a dangerous mix-up.

For more information on the tree's botanical properties, see the database at Useful Tropical Plants.

Conclusion: Prioritize Safety Above All Else

The question "is sea lettuce tree edible?" is best answered with a firm and unequivocal warning: do not eat the tree. The confusion stems from a shared common name with a safe, edible seaweed. While the marine alga, Ulva lactuca, is a safe and nutritious food source when collected responsibly, the Pisonia grandis tree is known for its toxic properties and animal-trapping seeds. Foraging requires absolute certainty of identification. In the case of the sea lettuce tree, that certainty points directly to potential danger, making it an item to avoid entirely.

Frequently Asked Questions

The primary difference lies in their biology and edibility. Sea lettuce the seaweed (Ulva lactuca) is an edible green algae found in the ocean. Sea lettuce the tree (Pisonia grandis) is a potentially toxic tree found in tropical regions.

The tree is dangerous for two main reasons: its sticky seeds, which are known to trap and kill small birds, and reports of its leaves containing toxic compounds that can cause illness in humans and pets.

Yes, the bird-catcher tree is another common name for Pisonia grandis, the same species referred to as the sea lettuce tree.

While some historical accounts mention the consumption of its leaves in specific cultures or cultivars, the edibility is highly disputed and it is officially listed as toxic to humans and pets. The potential risks make it unsafe to consume.

The seaweed is generally safe if collected from clean, unpolluted waters. Avoid areas near industrial runoff or during red tide events. Always wash it thoroughly before eating.

If you accidentally eat the Pisonia grandis tree instead of the seaweed, you risk poisoning, which can cause symptoms like vomiting and abdominal pain. If you suspect you have consumed the wrong plant, seek immediate medical attention.

The confusion stems from a lack of precision in common botanical names. Both organisms have large, somewhat leafy structures, and the name 'sea lettuce' was colloquially applied to both, despite them being entirely different species with different properties.