Examine your established pumpkin vine. Look for the best pumpkin on the vine; it should be uniform in color, free of soft spots or holes from borers, round, plump and firm. Do not choose a pumpkin with bruises, discoloration or mold.
Snip all of the other pumpkins from the vine. You may use them as decorative gourds or cook with them. The single pumpkin left on the vine will get all of the nutrients, helping it grow larger.
Pour about 1/2 cup of milk into a small bowl. Treat your pumpkin with 1/2 cup of whole milk each week or whenever you fertilize.
Place the tip of a surgical syringe, available with diabetic supplies or in farming supply stores, in the bowl of milk. Pull the plunger back, sucking all of the milk into the syringe. Gently push the plunger down a little so the milk squirts out. This eliminates air bubbles in the syringe.
Push the syringe into the stem of your pumpkin on the vine. Slowly inject the stem with all of the milk in the syringe. Poke a different place in the stem each time you inject milk; this gives the other holes a chance to heal and prevents infection in your pumpkin.