If your seeds are 136 blocks away from you, and they are not within the spawn chunck,they(their chunck,actually) will be unloaded ,and of course won't grow. This rule can also apply to the animal breeding. read more
Seeds must be planted on farmland, preferably irrigated. They will then grow into a pumpkin or melon plant, taking 10–30 minutes to do so. When the plant is mature pumpkin or melon will appear on a farmland, dirt or grass block next to the plant. speed up the growth of the plants by applying bonemeal. read more