Wet sponges contribute to tree growth too.

docs/roadmap.txt

@@ -9,8 +9,6 @@ ROADMAP: Large New Development Projects
  #    #  #       #    #     #    #       #       #   #   #    #
   ####   #        ####      #    ######  ######  #    #   ####
 
-- Make trees use all wet things (i.e. sponges) for water?
-
 - Stagger-delay some ABM actions per-node?
 
 - Doors

mods/nc_sponge/node.lua

@@ -26,7 +26,8 @@ minetest.register_node(modname .. ":sponge_wet", {
 		groups = {
 			crumbly = 2,
 			coolant = 1,
-			falling_node = 1
+			falling_node = 1,
+			moist = 1
 		},
 		sounds = nodecore.sounds("nc_terrain_swishy")
 	})
@@ -39,7 +40,8 @@ minetest.register_node(modname .. ":sponge_living", {
 		groups = {
 			crumbly = 2,
 			coolant = 1,
-			falling_node = 1
+			falling_node = 1,
+			moist = 1
 		},
 		drop = modname .. ":sponge_wet",
 		sounds = nodecore.sounds("nc_terrain_swishy")

mods/nc_terrain/node.lua

@@ -214,7 +214,7 @@ regliquid({
 		buildable_to = true,
 		drowning = 1,
 		drop = "",
-		groups = { coolant = 1, water = 2 },
+		groups = { coolant = 1, water = 2, moist = 2 },
 		post_effect_color = {a = 103, r = 30, g = 76, b = 90},
 		sounds = nodecore.sounds("nc_terrain_watery")
 	})

mods/nc_tree/cultivation.lua

@@ -86,8 +86,8 @@ nodecore.register_limited_abm({
 					if def.groups.soil then
 						d = d + def.groups.soil
 						w = w + 0.2
-					elseif def.groups.water then
-						w = w + def.groups.water
+					elseif def.groups.moist then
+						w = w + def.groups.moist
 						return false
 					else
 						return false