Aside from being a fun decoration around Halloween time, pumpkins are a delicious, gourd-like squash with very high nutritional value that can be enjoyed for many months from early autumn to late winter. Growing your own pumpkin patch can be a rewarding way to produce your own fruit for pies, soups, salads and other sumptuous pumpkin dishes. Fertilizing your pumpkin properly is an important step in producing a good crop.
Fertilizers have three main ingredients: nitrogen, phosphorous and potassium. On most fertilizer packages, there will be three numbers displayed in sequence (e.g. "5 - 10 - 5"); these numbers represent the percentages of each of these chemicals in the fertilizer.
If you're just getting started growing pumpkins, consider a balanced fertilizer, like a 5 - 10 - 5, to use throughout the growing season. Apply it every two weeks, and water it in thoroughly.
More Experienced Growers
If you have experience growing pumpkins, you might want to try a more varied regimen of fertilizers to get your pumpkins the right kind of nutrients through the various stages of their growth.
During the early growth phase, consider a more nitrogen-heavy diet of fertilizers. Nitrogen provides for leaf and vine growth, but be careful as it risks "burning" your plant. Don't apply it directly to leaves or vines. If your plant is looking green and healthy but not producing fruit, back the nitrogen off a little, and it will redirect its efforts from vine growth to fruiting.
When fruit set is beginning, switch to a higher concentration of phosphorous, like 5 - 15 - 5. Phosphorous is water-soluble and does no damage to the plant, so there is very little risk of over-fertilizing here.
After fruit set, start using a more potassium-rich fertilizer. Potassium promotes the growth of the fruits, but won't burn your plant. The only risk here is that way too much potassium will cause the pumpkin to outgrow its skin and explode.
Do a little mix-and-match experimenting throughout the season. Take notes on what different fertilizer concentrations do to your pumpkins, and use the best results next season.