Short answers, pulled from the story.
Mustard seeds come from three different plants: black mustard (Brassica nigra), brown mustard (Brassica juncea), and white mustard (Sinapis alba). The seeds range in color from yellowish white to black depending on which plant produced them, and each variety has slightly different growing times and yields.
Nepal ranked first in global mustard seed production in 2021, according to estimates from the UN Food and Agriculture Organization. Russia placed second and Canada third, with total world production that year reaching 532,769 tonnes.
Mustard seeds are ground into a powder and then mixed with water, vinegar, or other liquids to create the condiment. Roughly 1,000 seeds are used to prepare 8 ounces of mustard.
In South Asian cuisines, mustard seeds are fried until they pop to release their oils, and mustard oil (shorsher tel) serves as the primary cooking medium. The seeds are essential ingredients in spicy fish dishes like jhaal and paturi, and they are also used in pickles preserved in mustard oil.
In the Parable of the Mustard Seed, Jesus compares the Kingdom of Heaven to a mustard seed, describing it as the smallest of all seeds on earth that grows into the largest of all garden plants. The parable relates to faith and the Kingdom of God.
In a story attributed to Gautama Buddha from the fifth century BC, the mustard seed is used to teach a grieving mother named Kisa Gotami about the universality of death. The Buddha asked her to collect mustard seeds only from households that had never suffered loss; when she could find none, she understood that grief is shared by all people.