The same techniques used to plant winter and summer squash are used when planting pumpkin seeds, but in warmer climate regions, you can sow seed right into the soil once it has warmed up in spring and the danger of frost is past.
If you want to have pumpkins by Halloween, you should plant them in early to midsummer so fruit will mature in the fall. If pumpkins are planted too early, they may soften and rot before Halloween comes around.
Pumpkins prefer full sun, but it is one of the few vegetables that will thrive under partial shade. Just be sure to allow plenty of room for the pumpkins to grow — there will be some heavy growing vines.
To prep the pumpkin seeds for planting, you need to file the edges of the seed with a nail file (Image 1). You should file all edges of the seed lightly except the pointed end. Filing the edges makes it easier for moisture to get inside and for the leaves to emerge from the shell without damage. The shell is very thick and the leaves will sometimes have difficulty splitting open the shell.
To also help with germination, put the seeds in a jar filled with warm water for an hour or two to help the seeds sprout faster (Image 2). After soaking the seed, drain off the water and pour the seeds into a plastic bag and then seal the bag.
Just like with the squash, you plant the seeds in hills. For bush type pumpkins, you'll need 3 feet around each plant. For the vining type, allow as much as 8' to 10' between plants for the vining type. Vining pumpkins require a great deal of space to spread. A big pumpkin vine can grow 6" in one day.
For a raised bed, insert a soil thermometer into the ground to check the soil temperature. The soil temperature should be at least 70 degrees Fahrenheit. Next, use a garden hoe to build hills spaced 10' apart. Then dig out a pocket in the center of the hill and drop 3 to 4 seeds 1" deep into the hole. After firming the soil over the seed, use a garden hose set on fine spray to mist the mounds with water.
Pumpkins require a lot of water — about 1" per week. You will need to keep the soil evenly moist, but you want to keep water off of the leaves so be sure not to use an overhead sprinkler for irrigation. Use a garden hose equipped with a misting nozzle to lightly water the mounds.
Try to apply water to your plants early in the morning so excess moisture will not be left on leaves. Excess moisture can promote disease and pest problems. Watering should be slow and deep for pumpkins and squash. You want to moisten the soil down at least 6". Push your index finger down into the soil to check the depth of the moisture.
To increase the growing temperatures or protect the squash and pumpkins against pests when the plants are small, you can add lightweight row covers. They let light and water in, but keep the insects out. You can leave it over plants all summer, but be sure to remove the covers when plants begin to bloom so the blooms can be pollinated.
Squash and pumpkin depend on bees to pollinate the blossoms. Female flowers must be fertilized for you to get a pumpkin. Male flowers show up first and the female flowers arrive a week later. You can identify the female flowers by the swollen base just below the petals. It will look like a tiny pumpkin (Image 1).
If you don't see active bees in your garden, you can assist pollination by spreading the pollen by hand. You can self-pollinate by transferring pollen from male to female flowers by hand with an artist's brush (Image 2). Wearing gloves, you brush the male flower first to gather pollen and then brush the center of the female flower with the collected male pollen. Be sure to handle the delicate blossoms gently. Each flower is open for only a half a day, usually in the mornings. Then they fold shut and do not open again to next morning.
One week after blossoms appear, you should side dress the vines with fertilizer. Side-dressing means spreading the fertilizer close enough to the plants so that their roots can eat it up. After you see 3 or 4 fruits appear, you should then replace the row cover but not before thinning the vine with pruning shears.
If you want to grow the largest pumpkins in the neighborhood, you should thin the growth to one or two plants per hill and only allow one fruit to mature on a vine. Remove all but the best fruit when they grow to about the size softball. Just remember to water well and often and watch as the fruit grow bigger and bigger.