How to Grow a Giant Pumpkin

How do you grow an Atlantic Giant Pumpkin?

Last fall my family and I attended the Skagit Valley Giant Pumpkin Festival at a local nursery. There were about 10-20 mammoth pumpkins all competing for the grand prize.

The winner was a 1600 pound pumpkin and it's growers won $1000 in prize money.

The world record was set in 2016 with a pumpkin that weighed 2624 pounds. That's almost as much as a Volkswagon bug.

I've always been interested in growing a giant pumpkin and this year I decided to try. I bought one Atlantic Giant pumpkin seed for $5 at the festival and saved it until spring. The "mom" pumpkin it came from weighed over 1600 pounds.

While at the festival I got the scoop on how to grow a prize winning giant pumpkin and I'm sharing all the secrets with you.

Virtually all giant pumpkins are descended from a variety called Dill’s Atlantic Giant, which is widely available from seed companies.

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How long does it take to grow a giant pumpkin?

Start your seedlings in April and if you follow these instructions you will have a mammoth pumpkin by Halloween.

What do pumpkins need to grow?

• full sun
• slightly acidic soil
• Should been sown indoors and not planted until danger of frost is gone
• weekly fertilizer

Soil preparation

Using the correct soil is key to growing any kind of plant. If you want to grow a prize winning pumpkin you need to use the correct growing medium. You can find out what your current soil conditions by having a soil test done. This will provide you with the amount of soil nutrients currently in your garden and provide information to balance your soil in preparation for planting. Follow the report to amend your soil with compost or fertilizer. Chicken or Steer manure are great options for amending your soil. Make sure you till your soil and avoid walking on the loosened soil to prevent compaction near the vine.

I didn't bother having our soil tested. We live on a farm and I'm pretty sure our soil is excellent quality. If my pumpkin doesn't grow properly this year I might consider testing it next year.

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Germinate the seeds

Germinate in mid april for Atlantic Giants. You can put the seed on a moist paper towel overnight in a warm environment (80-85 degrees) and then plant the seed pointed side down in good quality potting soil. Grow the seeding indoors for a week or two before moving it outside.

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Early Season Plant Protection

Your plant will need to be protected early in the growing season. Many put their seedlings out mid to late May, before the last frost. In order to keep the seedling protected it is important to build a cold frame.

Before you plant your seed consider laying down a sheet of black plastic or other material to retain heat around your seedling. If using plastic be sure to place a drip hose between the plastic and the soil so you can still water the roots. And remember to provide a hole for your seedling.

 Planting your seedling in an elevated mound of soil inside your cold frame . you can put a light inside the cold frame for overnight warmth. Protect the plant from wind from late spring to early summer wind once the plant has outgrown the cold frame.

What is the best fertilizer for giant pumpkins?

Early season fertilizing and watering is recommended to provide superior plant growth prior to pollination. The recommended liquid solid ratio is 9-35-15. The first stage of fertilization should be based on providing phosphorus for root growth, gradually shifting to a more balanced formulation with more nitrogen as the vine grows. As time progresses, prior to setting the fruit, switch to a higher potassium formulation for development of the set fruit.

Pruning the vine

This is helpful to optimize resource availability. The main and secondary vines (those growing off the main vine) should be kept but any tertiary vines (vines that grow off the secondaries) should be pruned off. This keeps the plant from spending too much energy on vine growth and allows it to spend more energy growing that big pumpkin. Cut off any vines when they reach the end of your garden.

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Mounding the soil

Mounding the soil over the vine to create a double root system is a step that shouldn’t be skipped if you really want a huge pumpkin. Take your shovel and place the dirt over the vine. It's recommended to use the surrounding soil of your garden space versus different types of medium. Most of the prized pumpkins are located over 10 feet from the main tap root. Covering the main vine for 8-10 feet is a reasonable plan.

Pollination

Pollination involves selecting a female flower at least 10 feet from the main root tap. Because the growing season in Washington is fairly short you should try to pollinate any reasonable female flower as soon as you can. You may not be successful until late July.

The female has a fruit under the flower which is characterized by the segmented pistil located located in the interior of the flower. The male flower has a long slender stem with no fruit. Find a female flower with 5 or more segments (lobes).

A good female candidate should also a stem angle which is almost 90 degrees perpendicular to the vine. Pollination should not be left to the bees. Take the male flower. Pull off the petals and rub the stamen on the female’s pistil.

The female flower is only fertile for a few hours on the first day it opens  so try to do your pollination early in the day. You may want to protect your female flowers from heavy rain by covering them with a plastic cup, ensuring your best chance for pollination.

Vine positioning.

Vine positioning is required for  your main and secondary vines. Positioning the vines will provide a proper use of your growing area and reduce stem stress. Make sure the vine is perpendicular to the fruit. As the pumpkin grows the shoulders will extend forward, touching the vine and eventually stressing the vine and the stem.

Positioning the vines early so that the pumpkins grow away from them can eliminate this. If fruit sets on the left side of the vine , you can train the vine to the right and vice versa giving the shoulders more room. Make a U shape and give it some slack.

When the pumpkin is the size of a basketball you can slowly move the pumpkin perpendicular to the vine. The should be done in many small steps over the course of a week to avoid snapping the stem. Stem stress is very common in pumpkins over 200 pounds

Select a single fruit

This will optimize you chances of a big pumpkin and daily measurements will help you decide which fruit to keep. You may have several fruits on your vine with successful pollination and you will need to make a decision on which to select for your final pumpkin. Some people leave one fruit and some people leave two. Any more than two will limit your final size significantly.

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Shade protection should be provided to prevent cracks during the heat of summer. Build a frame around your pumpkin without stepping on any vines. You can use a blue tarp to shade the fruit .

Should you use milk to grow your pumpkin?

In short- no. There is some information online that recommends using milk to fertilize your pumpkin but in reality the fertilizers that I mentioned previously will work well enough. Using milk may attract insects, disease or cause the plant to rot.

Harvesting Your Pumpkin

When your pumpkin is big enough and you are ready to harvest it, cut it off of the stem. Now you are free to carve it or enter it in contests. Keep in mind if you are trying to move a 1000 lb pumpkin you may need a forklift or heavy machinery to move it.

After the season is over, keep the seeds for next year and share them with friends. You can eat the seeds but apparently they are really bitter.

Have you grown a giant pumpkin before? Let me know your tips in the comments and I will update this post as the season goes!