With the Tree function, I can draw arbitrary trees:
Tree[f, {1, 2, 3}] 
However, real trees grow from the ground to the sky. When I pass the TreeLayout -> Bottom option, the leaves become in the wrong order:
How can I make leaves appear in the correct order, in the graphical display of Tree with a root at the bottom? Is there a built-in way to do that, or should I write my own function that reverses leaves on the fly?
children[ent : Entity["Person", _]] := Replace[ent[EntityProperty["Person", "Children"]], _Missing -> {}]; children[_] = {}; NestTree[children, Entity["Person", "QueenElizabethII::f5243"], 2, ImageSize -> 1000] 
NestTree[Reverse@*children, Entity["Person", "QueenElizabethII::f5243"], 2, ImageSize -> 1000, TreeLayout -> Bottom] 
EDIT: For the example given in the comment below
bottomsUp[ tree_Tree] := (tree //. Tree[lbl_, br_List] :> temp[lbl, Reverse@br]) //. temp :> (Tree[##, TreeLayout -> Bottom] &) EDIT 2: or a little cleaner
bottomsUp[tree_Tree] := (tree //. Tree[lbl_, br_List] :> temp[lbl, Reverse@br, TreeLayout -> Bottom]) //. temp :> Tree origtree = Tree[Subscript[μ, {1, 2, 3, 4}, {5, 6}], {Tree[Subscript[μ, {1, 2}, {3, 4}], {Tree[Subscript[ι, {1}]^{1, 2}, {Subscript[ι, {}]^{1}}], Subscript[ι, {3}]^{3, 4}}], Tree[Subscript[μ, {5}, {6}], {Subscript[ι, {}]^{6}, id}]}] 
bottomsUp[origtree] 
Since there does not appear to be a built-in way to achieve what I want, here is my code (which is maybe a bit simpler than the other answer, although probably less efficient due to recursion):
bottom[t_?TreeLeafQ] := t bottom[Tree[root_, children_]] := Tree[root, bottom /@ Reverse[children], TreeLayout -> Bottom] Well, seems like my hunch was wrong. My code is about 5x faster:
tree = RandomTree[2000] RepeatedTiming[bottomsUp[tree];] (* {0.0446962, Null} *) RepeatedTiming[bottom[tree];] (* {0.0088462, Null} *)
Tree[f, Reverse@{1, 2, 3}, TreeLayout -> Bottom]$\endgroup$