How would that apply to plants? There's a similar problem of too many species worldwide: over 400,000. Even Europe is daunting with 9,875 plant species, while North America has over 20,000.
But I met a couple that were trying to see each of the 19 penguin species in world. That was quite a challenge because some of them are confined to remote islands in the Southern Hemisphere, but a manageable number.
So consider these Life List ideas for plant lovers: