For whatever reason, for the past 5 years, my Dwarves have not come in contact with a single underground crop, other than 2 species of underground tree.
No seeds or underground crops (cave wheat, pig tail, dimple cup, not even plump helmet) were available at embark, and the Dwarf Civ refuses to bring any, it's not even an option to suggest.
Plus, when I my cavern layers, there were no plants to gather, and other than the 3rd level Blood Thorns and maybe Goblin Wood (Whatever trees are purple), no vegetation at all in any of the three layers.
My world gen was a little bit tweaked, with the biggest changes being a large decrease in cavern openness, resulting in tons of tiny one square corridors, no underground water, and the History Period being 3000 years.
So I guess either the Dwarves of the World get their crops from underground now, and the crops not growing because of the world wide cavern narrowness made the crops never exist, or the first dwarf crops couldn't grow without water, or the crops were hunted to extinction in 3000 years or something.
Hasn't been a big problem, but I do have 3 Legendary Herbalists now. I do yearly gatherings of every plant on the surface, I have a giant aboveground farm that now thanks to food surplus is set to only grow sunberries, and I hunt Giant Eagles for their tasty meats. (Something like 3200 units of drink, 5200 some units of food, 3100 of it being prepared.)
But it was strange to not be able to do Plump Helmets, and interesting that I had to design a few walled in aboveground farms that would be impervious to attack (Though that turned out to be unnecessary, 3000 years makes goblins extinct fairly often.)