Tomatoes.

Tomatoes appear to work simple enough, until you harvest them
the first time: The plant stays! However, after the 3rd to 5th
harvest, the plant wilts and needs to be removed, since no more
tomatoes will grow on the plant. Per harvest you can get 1-2
tomatoes only. You can craft the tomatoes to tomato seeds, as
expected.

init.lua

@@ -12,5 +12,6 @@ of the license, or (at your option) any later version.
 
 dofile(minetest.get_modpath(minetest.get_current_modname()) .. "/melon.lua")
 dofile(minetest.get_modpath(minetest.get_current_modname()) .. "/corn.lua")
+dofile(minetest.get_modpath(minetest.get_current_modname()) .. "/tomato.lua")
 
 minetest.log("action", "[crops] loaded.")

tomato.lua

@@ -0,0 +1,154 @@
+
+--[[
+
+Copyright (C) 2015 - Auke Kok <sofar@foo-projects.org>
+
+"crops" is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as
+published by the Free Software Foundation; either version 2.1
+of the license, or (at your option) any later version.
+
+--]]
+
+local interval = 90
+local chance = 2
+
+minetest.register_node("crops:tomato_seed", {
+	description = "tomato seed",
+	inventory_image = "crops_tomato_seed.png",
+	wield_image = "crops_tomato_seed.png",
+	tiles = { "crops_tomato_plant_1.png" },
+	drawtype = "plantlike",
+	sunlight_propagates = true,
+	use_texture_alpha = true,
+	walkable = false,
+	paramtype = "light",
+	groups = { snappy=3,flammable=3,flora=1,attached_node=1 },
+	drop = {},
+
+	on_place = function(itemstack, placer, pointed_thing)
+		local under = minetest.get_node(pointed_thing.under)
+		if minetest.get_item_group(under.name, "soil") <= 1 then
+			return
+		end
+		minetest.set_node(pointed_thing.above, {name="crops:tomato_plant_1"})
+		if not minetest.setting_getbool("creative_mode") then
+			itemstack:take_item()
+		end
+		return itemstack
+	end
+})
+
+for stage = 1, 4 do
+minetest.register_node("crops:tomato_plant_" .. stage , {
+	description = "tomato plant",
+	tiles = { "crops_tomato_plant_" .. stage .. ".png" },
+	drawtype = "plantlike",
+	sunlight_propagates = true,
+	use_texture_alpha = true,
+	walkable = false,
+	paramtype = "light",
+	groups = { snappy=3, flammable=3, flora=1, attached_node=1, not_in_creative_inventory=1 },
+	drop = {},
+	selection_box = {
+		type = "fixed",
+		fixed = {-0.5, -0.5, -0.5,  0.5, -0.5 + (((math.min(stage, 4)) + 1) / 5), 0.5}
+	}
+})
+end
+
+minetest.register_node("crops:tomato_plant_5" , {
+	description = "tomato plant",
+	tiles = { "crops_tomato_plant_5.png" },
+	drawtype = "plantlike",
+	sunlight_propagates = true,
+	use_texture_alpha = true,
+	walkable = false,
+	paramtype = "light",
+	groups = { snappy=3, flammable=3, flora=1, attached_node=1, not_in_creative_inventory=1 },
+	drop = {},
+	on_dig = function(pos, node, digger)
+		local drops = {}
+		for i = 1, math.random(1, 2) do
+			table.insert(drops, "crops:tomato")
+		end
+		core.handle_node_drops(pos, drops, digger)
+
+		local meta = minetest.get_meta(pos)
+		local ttl = meta:get_int("crops_tomato_ttl")
+		if ttl > 1 then
+			minetest.set_node(pos, { name = "crops:tomato_plant_4"})
+			meta:set_int("crops_tomato_ttl", ttl - 1)
+		else
+			minetest.set_node(pos, { name = "crops:tomato_plant_6"})
+			meta:set_int("crops_tomato_ttl", 0)
+		end
+	end
+})
+
+minetest.register_node("crops:tomato_plant_6", {
+	description = "tomato plant",
+	tiles = { "crops_tomato_plant_6.png" },
+	drawtype = "plantlike",
+	sunlight_propagates = true,
+	use_texture_alpha = true,
+	walkable = false,
+	paramtype = "light",
+	groups = { snappy=3, flammable=3, flora=1, attached_node=1, not_in_creative_inventory=1 },
+	drop = {},
+})
+
+minetest.register_craftitem("crops:tomato", {
+	description = "Tomato",
+	inventory_image = "crops_tomato.png",
+	on_use = minetest.item_eat(1)
+})
+
+minetest.register_craft({
+	type = "shapeless",
+	output = "crops:tomato_seed",
+	recipe = { "crops:tomato" }
+})
+
+--
+-- grows a plant to mature size
+--
+minetest.register_abm({
+	nodenames = { "crops:tomato_plant_1", "crops:tomato_plant_2", "crops:tomato_plant_3" },
+	neighbors = { "group:soil" },
+	interval = interval,
+	chance = chance,
+	action = function(pos, node, active_object_count, active_object_count_wider)
+		if minetest.get_node_light(pos, nil) < 13 then
+			return
+		end
+		local n = string.gsub(node.name, "4", "5")
+		n = string.gsub(n, "3", "4")
+		n = string.gsub(n, "2", "3")
+		n = string.gsub(n, "1", "2")
+		minetest.set_node(pos, { name = n })
+	end
+})
+
+--
+-- grows a tomato
+--
+minetest.register_abm({
+	nodenames = { "crops:tomato_plant_4" },
+	neighbors = { "group:soil" },
+	interval = interval,
+	chance = chance,
+	action = function(pos, node, active_object_count, active_object_count_wider)
+		if minetest.get_node_light(pos, nil) < 13 then
+			return
+		end
+		local meta = minetest.get_meta(pos)
+		local ttl = meta:get_int("crops_tomato_ttl")
+		if ttl == 0 then
+			ttl = math.random(4, 6)
+		end
+		minetest.set_node(pos, { name = "crops:tomato_plant_5" })
+		meta:set_int("crops_tomato_ttl", ttl)
+	end
+})
+