| Growing a Giant Pumpkin
Almost all the world record pumpkins since 1982 have been grown in small backyard gardens. By following the tips below you could have a prize winning pumpkin in your yard too. Don't forget to start seedlings in May because the longer the growing season the more likely you are to produce a giant pumpkin by Halloween!
Soil Preparation
- Incorporate an inch or more of organic matter into the top layer of soil. Mushroom compost, aged cow manure or peat moss works perfectly.
- Test the soil pH using a kit purchased at a local nursery and then adjust soil pH to between 6.0 - 6.8 by adding sulfur to lower the pH or lime to raise it.
Starting Seeds
- Start seeds indoors in 6 inch peat pots to allow for a healthy and strong start. This will increase the likelihood of growing large pumpkins. In California May is the perfect time for sowing seeds.
Transplant Seedlings
- Transplant the seedlings once the first true leaves appear (crinkled edges) or when roots appear at the base of the peat pot.
Pumpkins love the sun. Choose a spot that receives 6 or more hours of direct sun every day.
Four to five seedlings are typically planted in the middle of a mound that is approximately three foot in diameter which is surrounded by a moat that is approximately four inches deep. This allows the roots to have easier access to water and keeps the water contained around the plant.
- Thin the plants to the strongest two or three plants once the vines start to grow.
- If planting more than one hill of pumpkins, make sure they are at least 10 feet apart to allow for adequate room for each vine.
Water
- During the seedling stage (first 2 to 4 weeks) keep the mound moist but not wet and water gently with a watering can to keep the soil from washing away.
- Once the plants are established water them by using drip irrigation or soaker hose. Infrequent, deep watering is best because it encourages deep root development and allows the soil surface to dry between watering.
Pollinate Flowers
- At eight to ten weeks after starting seeds, the first flowers will begin to appear. Female flowers are closer to the vine and sit on a fuzzy round base. Male flowers are more prolific than the females, usually appear before female flowers and sit on long thin stems. If bees are not prominent in your area you can hand pollinate the female flowers by using a small artist brush to gather pollen from the males and then painting the central portion (stigma) of the female flower.
- Pollinating is best done in the early morning before July 10th. The more time the pumpkin has to develop the longer it has to grow before harvest.
- If a female flower is not adequately pollinated pumpkins will not fully develop, and often will abort partially through the season.
 
Male Pumpkin Flower Female Pumpkin Flower
Prune Vines
- Pruning helps to strengthen the plant and allows it to thrive. Three to five primary vines growing from the center of the plant are ideal for large pumpkin production. They should grow in different directions around the center allowing side vines to grow but pinching them back before they cross.
Select the Most Promising Pumpkin
- As the pumpkins grow select two or three that are growing the fastest on each primary vine and remove the rest. This allows energy for growth to be directed just to those pumpkins.
Reposition Set Pumpkins
- Once pumpkins start growing the stem can be at a very acute angle to the vine which can cause stress on the vine and thus decrease the pumpkins size. The pumpkin will grow best with its stem positioned perpendicular to the vine. Reposition the vine and pumpkin slowly over a one to two week period using props until the stem is at a 90 degree angle with the vine. Be careful because the pumpkin is delicate at this time and can abort if not handled with care.
Fertilizer
- Give seedlings a fertilizer that emphasizes phosphorus (30) with an analysis of 15-30-15, then once fruit has set utilize a more balanced fertilizer such as 20-20-20. By late July (if planted in May) utilize a fertilizer with higher potassium content (29) with an analysis of 15-11-29 until the end of the growing season. Apply water soluble formulas over the entire plant area once per week.
- Stick to the principle of less is more. If your pumpkins are growing too fast they can tear themselves from the vine and explode.
We hope to hear about your prize winning pumpkin. Happy Gardening!
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