Fix space vine lag (#3452)

Fixes lag from plants processing forever instead of obeying the subsystem's tick interval. Also fixes a glitch where plants didn't continue to grow if not mature.

Fixes #3451.

code/modules/hydroponics/spreading/spreading_growth.dm

@@ -17,7 +17,7 @@
 		if((locate(/obj/effect/plant) in floor.contents) || (locate(/obj/effect/dead_plant) in floor.contents) )
 			continue
 		if(floor.density)
-			if(!isnull(seed.chems["pacid"]))
+			if(seed.chems["pacid"])
 				addtimer(CALLBACK(floor, /atom/.proc/ex_act, 3), rand(5, 25))
 			continue
 		if(!Adjacent(floor) || !floor.Enter(src))
@@ -82,14 +82,15 @@
 		//spread to 1-3 adjacent turfs depending on yield trait.
 		var/max_spread = between(1, round(seed.get_trait(TRAIT_YIELD)*3/14), 3)
 		
-		addtimer(CALLBACK(src, .proc/do_spread, spread_chance, max_spread), 1)
+		do_spread(spread_chance, max_spread)
 
 	// We shouldn't have spawned if the controller doesn't exist.
 	check_health()
-	if(neighbors.len || health != max_health || buckled_mob)
+	if(neighbors.len || health != max_health || buckled_mob || !is_mature())
 		SSplants.add_plant(src)
 
 /obj/effect/plant/proc/do_spread(spread_chance, max_spread)
+	set waitfor = FALSE
 	for(var/i in 1 to max_spread)
 		if(prob(spread_chance))
 			sleep(rand(3,5))
@@ -105,8 +106,8 @@
 				neighbor.neighbors -= target_turf
 
 /obj/effect/plant/proc/do_move(turf/target, obj/effect/plant/child)
-	child.loc = target
-	child.update_icon()
+	child.forceMove(target)
+	child.queue_icon_update()
 
 /obj/effect/plant/proc/die_off()
 	// Kill off our plant.
@@ -119,6 +120,6 @@
 			neighbor.neighbors |= check_turf
 			SSplants.add_plant(neighbor)
 
-	QDEL_IN(src, 1)
+	qdel(src)
 
 #undef NEIGHBOR_REFRESH_TIME