20 September 2026

This flower is a closeup from the field of yellow flowers at Sewickley Heights Park. Tickseed beggarticks or bearded beggarticks (Bidens aristosa) are pretty flowers but they make annoying seeds.

Fertilized flowers create “hitchhiker” seeds, each with two barbed prongs that grab whatever that brushes past the plant.

For instance, my sweater.

Beggarticks have a close relative that is also in bloom now. Spanish needles (Bidens bipinnata) have small yellow flowers and much longer seeds.

Each seed is topped by a tiny pitchfork of two to four spikes with downward-facing barbs. They are too easy to pick up in passing.

For instance, on another sweater.

Late September is prime time for seedy hitchhikers.