Mature mob-plants have a chance of self-harvesting if the tray lid is not closed.

code/modules/hydroponics/hydro_tray.dm

@@ -7,7 +7,7 @@
 	flags = OPENCONTAINER
 	volume = 100
 
-	var/mechanical = 1 //Set to 0 to stop it from drawing the alert lights.
+	var/mechanical = 1         // Set to 0 to stop it from drawing the alert lights.
 
 	// Plant maintenance vars.
 	var/waterlevel = 100       // Water (max 100)
@@ -300,6 +300,10 @@
 	if(prob(3))  // On each tick, there's a chance the pest population will increase
 		pestlevel += 0.1 * HYDRO_SPEED_MULTIPLIER
 
+	// Some seeds will self-harvest if you don't keep a lid on them.
+	if(seed && seed.can_self_harvest && harvest && !closed_system && prob(5))
+		harvest()
+
 	check_level_sanity()
 	update_icon()
 	return
@@ -360,14 +364,17 @@
 /obj/machinery/portable_atmospherics/hydroponics/proc/harvest(var/mob/user)
 
 	//Harvest the product of the plant,
-	if(!seed || !harvest || !user)
+	if(!seed || !harvest)
 		return
 
 	if(closed_system)
-		user << "You can't harvest from the plant while the lid is shut."
+		if(user) user << "You can't harvest from the plant while the lid is shut."
 		return
 
-	seed.harvest(user,yield_mod)
+	if(user)
+		seed.harvest(user,yield_mod)
+	else
+		seed.harvest(get_turf(src),yield_mod)
 
 	// Reset values.
 	harvest = 0

code/modules/hydroponics/seed_datums.dm

@@ -84,6 +84,7 @@ proc/populate_seed_list()
 	var/display_name               // Prettier name.
 	var/roundstart                 // If set, seed will not display variety number.
 	var/mysterious                 // Only used for the random seed packets.
+	var/can_self_harvest = 0       // Mostly used for living mobs.
 	var/growth_stages = 0          // Number of stages the plant passes through before it is mature.
 	var/list/traits = list()       // Initialized in New()
 	var/list/products              // Possible fruit/other product paths.
@@ -660,9 +661,9 @@ proc/populate_seed_list()
 		got_product = 1
 
 	if(!force_amount && !got_product && !harvest_sample)
-		user << "<span class='danger'>You fail to harvest anything useful.</span>"
+		if(istype(user)) user << "<span class='danger'>You fail to harvest anything useful.</span>"
 	else
-		user << "You [harvest_sample ? "take a sample" : "harvest"] from the [display_name]."
+		if(istype(user)) user << "You [harvest_sample ? "take a sample" : "harvest"] from the [display_name]."
 
 		//This may be a new line. Update the global if it is.
 		if(name == "new line" || !(name in seed_types))
@@ -728,6 +729,7 @@ proc/populate_seed_list()
 	new_seed.name = "new line"
 	new_seed.uid = 0
 	new_seed.roundstart = 0
+	new_seed.can_self_harvest = can_self_harvest
 
 	//Copy over everything else.
 	if(products)       new_seed.products = products.Copy()
@@ -979,6 +981,7 @@ proc/populate_seed_list()
 	display_name = "killer tomato plant"
 	products = list(/mob/living/simple_animal/tomato)
 	mutants = null
+	can_self_harvest = 1
 
 /datum/seed/tomato/killer/New()
 	..()
@@ -1190,6 +1193,7 @@ proc/populate_seed_list()
 	display_name = "walking mushrooms"
 	products = list(/mob/living/simple_animal/mushroom)
 	mutants = null
+	can_self_harvest = 1
 
 /datum/seed/mushroom/plump/walking/New()
 	..()
@@ -1810,6 +1814,7 @@ proc/populate_seed_list()
 	seed_noun = "nodes"
 	display_name = "replicant pods"
 	products = list(/mob/living/carbon/alien/diona)
+	can_self_harvest = 1
 
 /datum/seed/diona/New()
 	..()

code/modules/hydroponics/spread_plant.dm

@@ -15,8 +15,8 @@
 	var/obj/effect/plant/parent
 	var/datum/seed/seed
 	var/floor = 0
-	var/spread_chance = 40
-	var/spread_into_adjacent = 60
+	var/spread_chance = 100 //40
+	var/spread_into_adjacent = 100 //60
 	var/evolve_chance = 2
 	var/last_tick = 0
 	var/hibernating = 0
@@ -27,8 +27,8 @@
 /obj/effect/plant/New(var/newloc, var/datum/seed/newseed)
 
 	..()
-	if(!newseed)
-		newseed = DEFAULT_SEED
+	if(!istype(newseed))
+		newseed = seed_types[DEFAULT_SEED]
 	seed = newseed
 	if(!seed)
 		del(src)