When it comes to seeds, there is no standard size. Seeds are widely varied in shape and size. Consider the contenders for the extremes of seed size.
The world’s smallest seeds are produced by certain ephiphytic orchids. Seeds can be as small as 1/300th of an inch (85 micrometers). The weight of one of them is about 1/35,000th of an ounce (0.81 micrograms). By way of comparison, a typical grain of salt is about 300 micrometers in length. This tiny specimen can grow into a beautiful orchid that is known as an “air plant.” It does not grow on the ground in the dirt, but rather attaches itself to other plants, such as tree bark, and gathers moisture and nutrients from the air.
On the other end of the see spectrum is the massive seed of the Coco de Mer palm tree. The mature fruit can weigh up 66 pounds (30 kg) and can be up to 19.7 inches (50 cm) in diameter. The fruit, which requires 6–7 years to mature and a further two years to germinate, is sometimes also referred to as the Sea Coconut, Bum Seed, double coconut, coco fesse, or Seychelles Nut. The tree that springs from that massive seed can grow to be 112 feet (34 m) tall.