Here in the UK, where it's likely to be more difficult, because of the light and shorter summer, this is what I do, and has been successful over the past two years:
I sow one seed per 5 inch pot, on edge, in peat-based compost which has been inoculated with mycorrhizal fungus.
Water well, but not over-generously and put in a warm humid place. (I use heated propagators)
When they germinate, I put them onto a south-facing windowsill for a week, then it's into the frost-free greenhouse, all the while keeping the compost moist but not soaking wet..
Outside, around the time of seed sowing, I prepare the ground by digging out a barrowload of soil, putting a barrowload of well-rotted manure in the hole, and another of seaweed, along with a couple of handsful of fish, blood and bone, and a good handful of woodash. These mounds should be three feet apart either way.
Replace the soil on top to make a mound after mixing in with it a good handful of cornstarch.
Push a two foot length of 3" pipe into the mound, about 45 degrees, halfway in, about halfway between the centre and edge of the mound. It is through this pipe that you water
After hardening off for a week, drench the soil with compost tea & plant out the pumpkins, one plant per mound.
Do not allow to absolutely dry out, and, when flowers appear, pollinate the female (mini fruit behind flower, with males.
When pumpkins swell, support them off ground with tiles or a piece of wood, to stop rotting & add comfrey tea or other organic high potash feed.
They are best ripened on the vine, and for best shape, you can turn them a bit every week.
When the handles come off the plants easily, they are ripe.
Cure the skins outside for a week, weather permitting, then move to a cool, frost-free place for storage.
and I imagine it will need quite a large area for the vine to grow. It is interesting to know how much care going into growing pumpkins though.
vine looks like. When it is in full growing mode the leaves are much bigger and take up even more space.
