Humans spread seeds purposely by hand. Most pumpkin patches are planted in late May so they can be harvested by Halloween and Thanksgiving, according to the Gardener's Network. Most pumpkin seeds are spread by hand by casting them out over the moist land.
According to Think Quest, an education foundation, birds spread pumpkin seeds by landing at a pumpkin patch---or on a cracked-open pumpkin---and flying away carrying the seed. The pumpkin seed then falls in another pasture and spreads.
When someone plants a pumpkin seed or if a pumpkin breaks open and the seeds dry out, a heavy gust of wind can carry the seed into another patch of land, according to Think Quest.
According to Think Quest, heavy rainfall can create small rivers that can also spread seeds. Birds and animals may drop a pumpkin seed in a body of water that will carry the pumpkin seed somewhere else.
Small animals often eat pumpkin seeds because of their high nutrition content. Some pumpkin seeds will attach to these animals, which will then carry the seeds until they fall off of the animal. Other seeds will pass through the animal's digestive system and be excreted in another area.