Top 10 Things to Do to Grow a Giant Pumpkin

1. Good Soil Preparation. You need soil rich in orgainc matter (compost, humus, cow manure, earthworm castings). The soil should have a ph of around 6.8 and shouldn't be compacted.
2. Mycorizal Fungi. This unique fungus when it touches the roots will double the nutrients the the pumpkin can uptake and is friendly to the plant. The fungi needs to touch the roots so it should be added to your soil preparation and around the root ball or seed when planting. Applying compost tea is also a good way to build other friendly bacteria and fungi into your soil to build a proper food web.
3. Water. Depending on where you live in Colorado, soil type, and temperatures you should be adding about 1 3/4 inches of water per week to the plant. The rule of thumb is that the soil should always be at least lightly moist between waterings just under the soil surface.
4. Good Genetics. This one can't be emphasized enough. Dill's Atlantic Giant pumpkins is the only variety that will consistently get you a pumpkin over 300 pounds. But even then it won't necessarily get you a giant pumpkin. Good seeds can be found through coloradopumpkins.com or howarddill.com.
5. Vine Maintainance. Your secondary vines need to be maintained in a christmas tree pattern so the leaves can receive maxium sunlight. You should also prune the vines so they get no longer than about 15 feet on each side. Don't let side vines grow off your secondary vines unless you have a hole that you would like to fill.
6. Pumpkin Placement. You should grow only one pumpkin once you have your fruit set and it should be at least 10 feet out on your main vine.
7. Fertilization. Give small and regular feedings to your pumpkin plant. I prefer two to three feedings a week after the pumpkin plant is a few weeks old. Calcium, iron, nitrogen, phosphorous and potassium are all needed to grow a big pumpkin and they should be applied in the correct amounts at the correct times. Humic acid, earthworm castings, minerals, seaweed and fish fertilizers are also great plant boosters. Try to avoid high salt fertilizers. High quality organic fertilizers in my opinion are the best long term choice.
   
8. Vine burying. You should bury you main and side vines so that they can grow secondary roots to feed the plant.
9. Stem Placement. The stem of your pumpkin should be at a 90 degree angle to the main vine. This will help reduce stem stress as the pumpkin grows bigger. If the stem is at to much of an angle then there is a chance it will break and your season will be over.
10. Patients. Don't rush things. The growing season is a long one so don't over do it and have fun while you are doing it. You may have some small setbacks as the season goes on but pumpkin plants are very resilient so just let it grow.