If it is getting close to Halloween and your pumpkins are still green, there are a few things you can do to ripen them in time for trick-or-treaters. Pumpkins are like any other vegetable or fruit; they can ripen off the vine after they are picked.
For a pumpkin, the ripening process slows down on colder days and speeds up when the sun is present. Keep these two things in mind after picking your green pumpkins. Move the pumpkins so they are facing toward the sun. Placing the pumpkins in an open area facing the south exposes them to the most sunlight, since south-facing objects are in direct sunlight most of the day. The amount of sun the pumpkin gets is the main variable when trying to ripen them faster.
Speeding up Ripening
Make sure nothing is blocking the sun's rays. Wipe clean the surface of the pumpkins occasionally with a rag or towel. This removes dirt, grease and any film on the surface blocking the sun's rays. Also, remove any objects, such as pots, yard equipment, furniture or garden implements, that are casting a shadow on the pumpkins.
Rotating Pumpkins for Even Ripening
Rotate your pumpkins each day when setting them in the sunlight. This allows a different side to face the sun during the daytime. If one side ripens slower, turn that side toward the sun and keep it there longer as well. If your front porch gets more sunlight than the back porch, set the pumpkins on the front porch with the less-ripe side facing the sun.
Storing Pumpkins in the Cold
Another problem with ripening pumpkins outdoors is the weather. In fall, the temperature drops and this slows ripening. If possible, move your pumpkins inside the house on nights when temperatures drop below freezing. Then just bring the pumpkins back outside to get more sunlight. Or, store the pumpkins inside if your weather turns unusually cold during the day and put them in a warm, airy room with large windows and plenty of direct sunlight. This way the pumpkin will continue to ripen. Whenever the weather is cold, this environment is better suited for ripening a pumpkin off the vine than outdoors.