Arizona Giant Pumpkin Growers

How to Grow A Giant Pumpkin
Do you want to learn how to grow a BIG PUMPKIN? We're here to help.  Follow these guidelines and you will have what’s required to get the job done.

However, be warned, if you ask 10 competitive pumpkin growers how to grow a giant pumpkin, you're likely to get 10 different answers. Everyone has his, or her, own way of coaxing the most weight out of these giants. But there are some consistent threads that runs throughout everyone's instructions, and adhering to four basic tenets will get you on your way.

In short, above all else, remember what Gordon Thomson said when he set the world record in 1984; “
All you need is a good seed, good soil, good weather, and good luck.”  (And I'm sure, now that he's had more time to think about it, he would add that you shouldn't forget the hard work involved in growing a giant pumpkin).

GOOD SEED - If you want to grow a world-record pumpkin, you can forget about every variety of pumpkin out there except Howard Dill's patented Atlantic Giant. Since 1979, no other pumpkin variety has been a world champion.

GOOD SOIL - Pumpkins are large consumers of all the major plant nutrients (nitrogen, phosphorus and potassium), as well as many minor nutrients like calcium and magnesium and other trace elements. Try to find out what your soil conditions are currently, and consult your local County agencies to see if they offer soil testing. A soil test will tell you the amount of soil nutrients your garden contains and provide corrective action to balance your soil for planting. Follow what they say and amend your soil with the compost or fertilizer of your choice. Of course there are many types of products to amend your soil. A key for pumpkin growth is soil well amended with organic matter. In the fall or early spring, add two to ten yards per plant of compost and composted manures. Cow and horse manures are best. Use chicken manure only in the fall (in Phoenix, growers add manure in June – once their season ends). The soil pH should be between 6.5 and 7.5.

HARD WORK - If you just throw some seeds into ground and water them every so often then chances are you aren’t going to grow anything decent. Proper care of your plant and pumpkin will greatly increase your chances of growing a big one.

GOOD WEATHER – You can't control the weather, but it's important you take the time to understand not only today's weather, and the 10-day forecast – but also the norms for your growing season. Phoenix area growers have found their giant pumpkin season runs from January through May; while higher elevation growers find the traditional May though September works for them. (NOTE: Phoenix growers build shelters, and heat the soil, to help their young plants during the cold January and February weather. Then once the heat begins to warm Phoenix in March, April, and May; then the greenhouse plastic is removed and replaced by shade cloth to help protect it from the intense sun and cool the plant.

GOOD LUCK - If you can grow a good vegetable garden, you have the skill to grow a world-record pumpkin. With good seed, and help from an experienced grower – and lots of luck – it is possible to grow an obscenely large pumpkin in Arizona. With the right preparation and strategy now and in the spring next year you might just be a contender.

Steps For Growing A Giant Pumpkin

1. PREPARING SOIL --  Soil Preparation is the key for any type of plant growth. We’re not growing a Xeriscape fruit. Pumpkins require the correct soil medium to grow to a healthy prize-winning pumpkin. Consult your local soil lab, have your soil tested, and find out what your soil conditions are currently. The soil test will provide the amount of soil nutrients your garden contains and provide corrective action to balance your soil for planting.

The soil lab will provide the test results which will include the percentage of nitrogen, phosphorus and potassium fertilizer needed to correct deficiencies; these percentages are the three numbers found on most fertilizers bags.. Follow what they say and amend your soil with the compost or fertilizer of your choice. Of course there are many types of products to amend your soil.  Some people plant a cover crop in the winter and amend the soil with additional manure to give it that extra punch. Be sure to till your compost in well to provide a good planting medium.

Apply fresh manure after the end-of-season (Phoenix growers – June; Everybody else – October).

Apply compost or composted manure prior to planting in the spring (Phoenix growers – add in the fall). Add up to 6 inches where you expect to plant.

2. SOWING SEEDS --  Start seed indoors in six-inch peat pots, 120-150 days before harvest. Round ½ gallon ice cream containers also work well. Cut the bottom off and turn upside down using the lid as the bottom. I recommend buying a high quality potting medium that can be purchased at your local nursery store. Plant the seed flat, ½ to 1 inch deep. Keep the soil temperature at 85 to 90 degrees F. Most seeds will emerge within five days.

3. TRANSPLANTING SEEDLINGS --  Transplant seedlings into the garden once the first true leaves appear usually seven to 10 days after germination. Handle with care because pumpkin plants are easily damaged during transplanting. The main vine grows the opposite direction of the first true leaf. If using an ice cream container, dig the planting hole, set in place, orient the plant, take the bottom off and then lift the contain up carefully past the plant.

4. PROTECTING SEEDLINGS --  Place a "mini-greenhouse" over the seedlings for six weeks to shield plants from wind and frost.  A simple hoop house can be made from PVC pipe, rebar and plastic. Make a frame by taking one 10 ft. pvc pipe (or two 10 ft pvc pipes joined together if you want more head room) and sliding it over two pieces of rebar (3/8 inch diameter, 2 ft long) that are about 6 ft apart and have about 8-10 inches above ground and are at an angle. 
Add additional frames at 4-6 ft apart to complete the hoop house structure. Cover with clear plastic. Cover the ends too. Cut the plastic so that there is extra around the edges. Bury the extra plastic to seal the warm air in and keep the wind from blowing inside the house. Be careful on sunny days the temperature inside a hoop house can reach 100°. Making slits as vent or opening the sides helps cool things down on sunny days.

5. TRAINING & BURYING VINES --  Train the main vine to run down the middle of your patch. Train side shoot, secondary vines, so they are perpendicular to the main vine to accommodate access to the vines and pumpkins. Pinch or cut off all other vines, tertiary vines, coming off the secondary vines. Bury the vines by placing a shovelful of dirt where each leaf meets the vine. Let each leaf grow above the vine before burying. Do not bury the vines where you see and plan on pollinating a female flower.

6. BUGS & DISEASES --  Contact a local grower or your local county extension. They can either be a huge problem or none at all depending on where you live.

7. POLLINATING FLOWERS --  Eight to 10 weeks after seed starting, the first female flowers will appear. The female has the fruit under the flower and the male is long slender stem with a flower on top. Now we have discussed the difference, find a female plant with the correct angle on the vine.

A good female candidate should have a stem angle which is as close to 90° (perpendicular) as possible to the vine. If the stem is at an acute angle, then it will be more likely to be damaged or split as the pumpkin grows.

You'll want to hand-pollinate the flowers. In the early morning, locate a freshly opened male flower. Pick it and remove the outer flower petals, exposing the stamen and fresh pollen. Locate a newly opened female flower and gently swab the stigma (internal parts) of the female flower with the pollen-laden stamen. Many people prefer to use a paint brush with camel hair. This is a standard method in the horticultural world. But many growers also peel off the pedal on the male flower and rub the male stamen on the female stigma.

Getting a pumpkin set early, preferably before July 10-20th (Phoenix – March 1-15th, is an important step. The earlier you set a pumpkin, the longer it has to grow until harvest. Since these monsters can gain 25 pounds a day, losing 10 days in the early part of the season could put you well down the list at your local pumpkin weigh-off.

8. REPOSITION SET PUMPKINS --  Once a pumpkin has set, its position on the vine becomes extremely important. Most often the stem does not grow at 90° to the vine. However, for optimal long-term growth, the best position is to have the stem perpendicular to the vine. When the pumpkin is about the size of a basketball you can slowly move the pumpkin perpendicular to the vine. This should be done in small steps over a period of a week or you will snap it off. There is no warning when the pumpkin is about to crack off so go slow and 
don't move it much each day. In some cases it is easier to reposition the vine away from the pumpkin. You can do both.

9. SELECT THE MOST PROMISING PUMPKIN --  If one plant has three strong vines, you could have as many as seven or eight pumpkins set and growing by July 20. Now you must choose the best pumpkin and remove most of the rest. Measure each pumpkin's circumference at the widest point weekly or daily with a cloth measuring tape. Choose the one that's growing fastest. Also, keep an eye out for the optimum shape. Young pumpkins that are round and especially tall grow the largest. Pumpkins on the main vine usually grow larger than pumpkins on secondary vines.

As a pumpkin grows, the shoulders will extend forward, often touching the vine. Also as the pumpkin grows taller the stem will be pulled downward. Cut off the tap root at the pumpkin and as needed on either side of the pumpkin. A pumpkin can pick itself if the vine is not lifted up and supported to match the height of the stem. It is also a good idea to curve the vine in a “C” shape where the pumpkin is to create extra slack in the vine, with the pumpkin in the middle on the out side of the “C”. As the pumpkin grows taller the extra slack in the vine will be used. Side vines can also wrap around the large pumpkin and cause damage. Train the side vines away from the area where the pumpkin will eventually be so there is room. Remove the leaf at the junction where your pumpkin is, to prevent scratching and damage. It is usually necessary to remove the secondary vine where your pumpkin is to allow extra room for it to grow.

Before your pumpkin gets to large you will want to place it on something to protect it from rodents, potential rot from the bottom side and to keep the bottom side flat. Many growers use wood or ply wood with sand or landscape fabric on it. Others like to use just plain sand or Styrofoam. Make sure that water will drain off what ever you use.

Shade protection should be provided to prevent premature aging of your pumpkin. Build a mini-hoop house over your pumpkin carefully avoiding the vines. Many growers use a standard blue tarp but some growers swear that orange tarps are the way to go. Take this down two to four weeks before harvesting to increase pumpkin color and to help harden up the skin.

10. TERMINATING VINES --  Cut off and bury the end of the main vine when it has reached 10 to 12 feet beyond a set fruit. If you have a pumpkin on a vine that is 10 feet from the main root, cut the end of that vine once it is 20 to 24 feet long. Terminate the secondary vines when they are 8-12 ft long. Usually at the boundary of your patch. Bury them also.

11. FERTILIZING --  During the growing season, most fertility needs of pumpkins can be met by applying water-soluble plant foods once or twice a week over the entire plant area. Give seedlings a fertilizer that stresses phosphorus, such as 15-30-15. Shift to a more balanced formula, such as 15-15-15, once fruits are set.

By late July (Phoenix – March), continue with a 15-15-15 formula to obtain maximum fruit growth. Apply water-soluble fertilizer at the rate of one pound per week per plant from fruit set until the end of the growing season. Some competitive growers will error on the side of over fertilization. But too much fertilizer can hurt more than help. If the pumpkins start growing too fast, they will literally tear themselves apart. A legendary grower in New England has often said, "Slow and easy wins the race." Remember this whenever you feel the urge to over fertilize. The better your soil is the less fertilizer you will need to use. Adding lots of organic matter, OM, (compost, manure, etc) is key.

12. WATERING --  Giant Pumpkins require approximately 1 to 1 ½ inches per week. The amount of water required can vary greatly depending on soil type, temperature, humidity, time of year, etc. Once you get a feel for your patch you can better adjust to your own watering needs. But many growers need a good starting place. To cover a 1000 square foot garden evenly with 1 inch of water it takes 623 gallons. (1 gallon = 231 cubic inches) That’s a lot more than many growers might think. This is 89 gallons per day, or 178 gallons every other day. For 1 ½ inches of water per week it takes 934.5 gallons per week, or 133.5 gallons per day, or 167 gallons every other day.  Again, we're not talking Xeriscape gardening here.

13. KEEPING TRACK --  Measure your pumpkins at least weekly. Gains in circumference can average four to six inches in a 24 hour period. Measure the circumference of your pumpkins first parallel to the ground around the entire pumpkin, from blossom end to stem. Next, measure over the top in both directions: from ground to ground along the axis from stem to blossom end, then perpendicular to the stem-blossom-end axis. Add these together to obtain a, Over the Top, OTT measurement. Look up the OTT on OTT vs. Weight Table to find your estimated weight.
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