Selecting a planting site
1) Select a sunny place in your garden. Giant pumpkins thrive best in strong sunshine. The larger the area, the better (500-1,000 sq. ft.), but smaller areas have been successfully planted too. An area that receives 8-12+ hours of sunlight, per day, is ideal.
Preparing the soil and mound
1) The best pumpkins come from the best prepared soil. Dig a hole, 40”-48” deep, 2’-5’ in diameter, and mix the soil well with 6-8 bags (9-12 cubic feet) of soil amendments and/or other high organic content materials: well-aged steer or horse manure, compost, humus. More is better!
2) Put the mixed soil back in. You should have a mound, 2’-5’ in diameter, 20”-24” high at its center.
3) Allow 35’-50’ between individual mounds if you are planting more than one vine.
Germinating giant pumpkin seeds
1) Soak seeds overnight in warm water (8-12 hours.) This softens the pumpkin seed’s shell and accelerates germination. Start germinating seeds mid-late April to early-mid May. Rinse any tools, utensils, or containers that may come in contact with seeds with a 1/9, bleach/water solution to sanitize all surfaces.
2) Plant seeds in a 4” minimum or larger peat/coir pot, in a seed starting mix, flat, .75”-1.0” deep.
3) Keep seeds moist and warm, 75-80 degrees F. range, is ideal.
4) Under these conditions, seeds should sprout in 3-5 days, sometimes even sooner!
5) After the seedling has developed 1-2 true leaves, it is ready to transplant into the mound.
6) Or, you may simply sow your seeds directly into the mound. Competitive giant pumpkin growers have successfully used both methods.
1) Plant the seedling, peat pot and all, in the center of the mound. Peat pot should be well below the top surface of the mound. Soil surface should be just below the bottom leaves. Transplanting in the late afternoon/early evening will help reduce dehydration, initial sun and wind damage. Water thoroughly. An application of mycorrizhae fungus at this stage will assist early root development.
2) Protect the seedling from winds, strong sunlight, insects and other potential damage by placing an open cardboard box around the seedling until it gets fully established, usually, 7-10 days.
Watering, fertilizing & general care
1) Pumpkins are 90% water. Soil should be kept moist. Water daily, to once every 2-5 days, depending on your weather and soil conditions. Watering times should be consistent. Early morning (5:00 a.m.-8:30 a.m.) is the best time to water.
2) Use an organic fertilizer every 5-10 days. Seaweed (kelp) and/or fish hydrolysate are some of the fertilizers currently being used by competitive giant pumpkin growers.
3) Mulch around the main stem with compost, straw, or well-aged manure, 3”-4” deep. Leave 6”-9” of clearance around the stem. Mulching will help regulate soil temperature, help soil retain moisture and better distribute water and nutrients. To help prevent and treat powdery mildew, applying organic potassium bicarbonate as a foliar spray has been an effective treatment.
4) Place a wooden pallet/or some several shovelfuls of coarse sand underneath the pumpkin before it gets difficult to move (10-25 pounds) to keep the pumpkin’s bottom from rotting, and to facilitate lifting and transporting it later.
5) Shade the pumpkin once it reaches 24”-36” in diameter to help keep the pumpkin’s skin from hardening and cracking from the hot, mid-late summer/early fall sunshine.
6) Many competitive growers bury all of their vines, with just the leaf stalks and leaves uncovered. This promotes rooting of the vine.