diff --git a/growth.lua b/growth.lua
index aec2e95..56ba4ef 100644
--- a/growth.lua
+++ b/growth.lua
@@ -1,3 +1,5 @@
+local time_scale = ...
+
 -- The growing ABM
 
 function biome_lib:grow_plants(opts)
diff --git a/init.lua b/init.lua
index c8777fd..1308a1a 100644
--- a/init.lua
+++ b/init.lua
@@ -201,7 +201,7 @@ end
 -- Function to check whether a position matches the given biome definition
 -- Returns true when the surface can be populated
 
-local function populate_single_surface(biome, pos, perlin_fertile_area)
+local function populate_single_surface(biome, pos, perlin_fertile_area, checkair)
 	local p_top = { x = pos.x, y = pos.y + 1, z = pos.z }
 	local noise1 = perlin_fertile_area:get2d({x=pos.x, y=pos.z})
 	local noise2 = biome_lib.perlin_temperature:get2d({x=pos.x, y=pos.z})
@@ -291,7 +291,7 @@ function biome_lib:populate_surfaces(biome, nodes_or_function_or_model, snodes,
 
 	for i = 1, #snodes do
 		local pos = vector.new(snodes[i])
-		if populate_single_surface(biome, pos, perlin_fertile_area) then
+		if populate_single_surface(biome, pos, perlin_fertile_area, checkair) then
 			in_biome_nodes[#in_biome_nodes + 1] = pos
 		end
 	end
@@ -468,20 +468,11 @@ function biome_lib:generate_block_no_aircheck()
 	end
 end
 
--- "Record" the chunks being generated by the core mapgen
-
-minetest.register_on_generated(function(minp, maxp, blockseed)
-	biome_lib.blocklist_aircheck[#biome_lib.blocklist_aircheck + 1] = { minp, maxp }
-end)
-
-minetest.register_on_generated(function(minp, maxp, blockseed)
-	biome_lib.blocklist_no_aircheck[#biome_lib.blocklist_no_aircheck + 1] = { minp, maxp }
-end)
-
 -- "Play" them back, populating them with new stuff in the process
 
+local step_duration = tonumber(minetest.settings:get("dedicated_server_step"))
 minetest.register_globalstep(function(dtime)
-	if dtime >= 0.2 -- don't attempt to populate if lag is already too high
+	if dtime >= step_duration + 0.1 -- don't attempt to populate if lag is already too high
 			or math.random(100) > biome_lib.queue_run_ratio
 			or (#biome_lib.blocklist_aircheck == 0 and #biome_lib.blocklist_no_aircheck == 0) then
 		return
@@ -664,9 +655,8 @@ function biome_lib:replace_object(pos, replacement, grow_function, walldir, seed
 end
 
 
-
 dofile(biome_lib.modpath .. "/search_functions.lua")
-dofile(biome_lib.modpath .. "/growth.lua")
+assert(loadfile(biome_lib.modpath .. "/growth.lua"))(time_scale)
 
 
 
diff --git a/search_functions.lua b/search_functions.lua
index 92a82ea..d665b5f 100644
--- a/search_functions.lua
+++ b/search_functions.lua
@@ -51,3 +51,10 @@ function biome_lib:find_open_side(pos)
 	end
 	return nil
 end
+
+-- "Record" the chunks being generated by the core mapgen
+
+minetest.register_on_generated(function(minp, maxp, blockseed)
+	biome_lib.blocklist_aircheck[#biome_lib.blocklist_aircheck + 1] = { minp, maxp }
+	biome_lib.blocklist_no_aircheck[#biome_lib.blocklist_no_aircheck + 1] = { minp, maxp }
+end)