Here's why:

* Cytisine: The seeds, pods, and even the bark of the laburnum tree contain a toxic alkaloid called cytisine. This substance is very similar in effect to nicotine and can cause serious poisoning.

* Symptoms: Ingestion of laburnum seeds can lead to a range of symptoms, including nausea, vomiting, diarrhea, drowsiness, seizures, and even death.

* Especially dangerous for children: Laburnum seeds are particularly dangerous for children who might be tempted to eat them due to their colorful appearance.

* No antidote: There is no known antidote for laburnum poisoning, so immediate medical attention is essential if someone has ingested any part of the tree.

Important Note: While the flowers of the laburnum tree are generally considered safe, it's best to avoid any contact with the seeds, pods, or bark. If you have a laburnum tree in your yard, it's crucial to educate children about the dangers and keep them away from the seeds.