diff --git a/plants_lib/init.lua b/plants_lib/init.lua
index edda1dc..b303cd7 100644
--- a/plants_lib/init.lua
+++ b/plants_lib/init.lua
@@ -373,8 +373,8 @@ function plantslib:replace_object(pos, replacement, grow_function, walldir, seed
 		return
 	elseif growtype == "string" then
 		local perlin1 = minetest.env:get_perlin(seeddiff, perlin_octaves, perlin_persistence, perlin_scale)
-		local noise1 = perlin1:get2d({x=p_top.x, y=p_top.z})
-		local noise2 = plantslib.perlin_temperature:get2d({x=p_top.x, y=p_top.z})
+		local noise1 = perlin1:get2d({x=pos.x, y=pos.z})
+		local noise2 = plantslib.perlin_temperature:get2d({x=pos.x, y=pos.z})
 		plantslib:dbg("Grow: call function "..grow_function.."("..dump(pos)..","..noise1..","..noise2..","..dump(walldir)..")")
 		assert(loadstring(grow_function.."("..dump(pos)..","..noise1..","..noise2..","..dump(walldir)..")"))()
 		return