Yes. In addition to providing nutritious greens, this plant also produces the seeds that are used as a spice and to make prepared mustard, such as Dijon, brown, and yellow.
No. Dry mustard is powdered Mustard Seed. Turmeric is another spice usally added to prepared mustard.
Pigments such as chlorophyll. See related questions
A mustard color
Mustard is made from a plant's Seeds.
Mustard plants reproduce through seeds.
Only one plant comes out from a mustard seed.
I'm pretty sure there is no such thing as a mustard tree but there are mustard plants.
They Die.
Yes
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Kelp can be green or mustard colored.
Presuming you mean mustard plants, then presumably, yes. They only need moisture to grow.