The biggest seed of this world is double coconut, it's a native palm tree of the Seychelles Islands. The flowers are borne in enormous fleshy spadices (spikes), the male and female on distinct plants. The single-seeded fruit weighs up to 20 kg (44 lb) and can take 10 years to develop.

Pciture 1:  Double coconut

 Pciture 2:  3 double coconuts

Pciture 3:  A big double coconut

 Pciture 4:  The male flower