This random table/generator is adapted from u/MortalBean's post at r/d100. It includes a filter to allow the user to select the rarity of the plants.

From the post:

I hope I'm not the only one who is tired of endless wheat farmers in D&D. These plants largely focus on farmed crops, but some herbs are included as well. I've done my best to sort out what would and wouldn't have been available in medieval Europe but I'm really not an expert on these things so there may be some mistakes. I've included new world plants largely because in a fantasy world with modern players, these plants may be around. I've included specific die rolls if you wish to get a plant from a particular group of plants.

• 1-39 (d39) are plants which likely were cultivated or widely available in at least one location in medieval Europe.
• 40-51 (d12 + 39) are plants which may or may not have been cultivated but were probably at least growing in the wild in medieval Europe.
• 52-67 (d16 + 51) are plants which I'm fairly sure were only found in the wild in medieval Europe.
• 68-100 (d33 + 67) would have been largely or completely inaccessible in medieval Europe. Specifically the spices on this list would likely have been available but prohibitively expensive.