Secrets of Fertilizing a Giant Pumpkin

Do you want to know the secret giant pumpkin fertilizer program to grow a 1,000+ pound pumpkin?  The answer: there really are no secrets.  There is a lot of available good science available however that gives a grower some guidelines to growing their biggest pumpkin ever.  But the truth be told, this is an evolving science that continues to get refined with time and more study, because no company funds big studies on giant pumpkins.

So to answer the most asked question when it comes to fertilizing, "What is the best pumpkin fertilizer?"  The simple answer is that it is the one the plant needs at the time.  Most growers that grow a 1,000 pound pumpkin get soil tests in the spring/fall or both.  Some will also get tissue tests done prior to pollination on the plant to see what it is lacking.  Those tests and the recommendations that come with them are a guide to the grower on what to add.  But they don't give you much in the way of direction for when to add.  Because of this I created my fertilization guide in 2015 that I've updated over the years:

Giant Pumpkin Secret Fertilization Program

That guide gives you the when, but not so much on how much to add.  The soil test recommendations will kind of give you that.  But only one lab that I know of has ever done any studies on how much a giant pumpkin needs.  Western Labs did that I believe in 2008 and it was a pretty well done study utilizing top growers.   The recommendations from it can be found here:

View Study Fertilization Recommendations

I saw Jon Taberna do a presentation of the results of his study and a couple of things that stood out to me from that presentation is Jon's amazement with how the Atlantic Giant Pumpkin plant can adjust and take up what it needs on demand more so than most other crop type plants.  Also, how much demand for potassium a giant pumpkin requires.

The most recent larger scale study on Atlantic Giant pumpkin plants was done by Don Chambers in his Giant Pumpkin Soil Study, which I believe concluded last year.  Charts below are from his study:

View Giant Pumpkin Soil Study

From the study of 221 pumpkins this was the average of nutrients in the soil for plants the produced 1,200+ pound pumpkins:

So, keeping in mind that many soil testing labs haven't done recommendations for amendments for giant pumpkins, the recommended amounts of amendments might be too low based on what this study has found.  Those recommendations are based on standard crops, not 1,200+ pound pumpkins.

Also, another thing to keep in mind.  Soil type matters.  More sandy soil will leach nitrogen and some micro nutrients much faster than others, so sometimes timing of when amendments are to be added and how much will need to be adjusted based on that.  Also, the amount of organic matter affects timing.  If you have high OM, as that soil warms up during the season, it is going to release ammonia and other nutrients into the soil.  Timing and balance are keys in growing a giant pumpkin.

One other thing to remember when it comes to giant pumpkin plants.  The soil may be full of nutrients, but what is available to the plant is just the small area around the root hairs.  If demand for example is high for potassium during rapid pumpkin growth, then the plant can get deficient, event though the soil may be a too high in potassium.  So that is why I recommend spoon feeding during the season small amounts at regular intervals.  

Growing a giant pumpkin is a wonderfully complicated process, but by not doing too much or two little you can optimize growth and achieve a personal best giant pumpkin in 2021.

What I'm Going to Do Different in the Pumpkin Patch in 2021 to Grow Bigger

We'll it has been too long since my last post.  Some health problems that cause me pain and fatigue have been a bit of problem, but I won't let that become an excuse.  Right now I'm a bit behind in the patch, but will get everything cleaned up and tilled by the last week of March I'm hoping.  I'm only going to grow one pumpkin this year and that will be in the greenhouse, so I can focus all of my energy on it.  I haven't got the seeds I want to grow yet, so I'll announce those once I have them in hand.

So how do I grow bigger in 2021?  I've got some plans.  The first will be to fertilize more.  Particularly nitrogen in the earlier parts of the season and potassium in the later parts of the season.  I don't think I've been getting my foot to the floor.  The year I grew my biggest pumpkin was the same year I fertilized the most.  A coincidence?  Maybe not. 

I'm also going to start giving the plant extra potassium earlier.  Typically I ramped it up about 20 days after pollination.  This year I'm going to start ramping it up about 7 days before pollination.  I want the plant to feel it has everything it needs to be put energy towards the pumpkin, so an appropriate earlier ramp up I think can help with that.

 I'm going to motorize the greenhouse side wall roll ups and put them on smart plugs.   That will save me some time each day that I can put into growing the plant because I'll be able to roll things up and down from my phone anywhere in the world.

I've been talking with a grower this afternoon about water pH and going to try something that Mehdi (who has grown a number of 1 ton pumpkins) has been doing.  That is adding citric acid to the water to help lower pH in the soil.  pH above 7.0 can cause some issues with nutrient uptake.  Elemental sulfur and compost can help lower soil pH, but when you water every day with water that is 7.4+ it makes it hard to do much of anything to get the pH down to 7.  So we'll see if this strategy can help.

this year I'm going to close off by back roll-up door to see if I can run CO2 longer by having the top foot of the roll up door so I can vent heat but keep the CO2 trapped inside.

I'm replacing all of the fogger nozzles this year.  I had a lot of trouble with clogs this last year, which I didn't have the year before, so we'll see if that helps.

I'm also replacing the hot water heater.  Last year's literally blew up mid-season so I didn't get much value out of it. 

Late Fall Pumpkin Patch Prep

 This is the latest I believe I've ever prepped the pumpkin patch soil.   Actually I'm still not fully done.  Usually in mid-October I'll amend and till the soil.  Between work, health, precipitation, wind and frozen ground I haven't had a chance to work the ground.  I was actually getting worried, because this time of year the soil can be covered by snow or frozen where nothing could be done till spring.  I got lucky however and got a warm enough streak for a few days that ground dried out just enough I was able to put in some mulched leaves, nitrogen, potassium and sulfur into the soil.  Those leaves should be fully broken down by spring, at which time I'll send in a soil sample into the lab and then do my final amendments and tilling at that time.

You have to be a little careful when adding leaves as well as any other amendment.  With leaves it is easy to add too much and get your potassium to high in the soil.  It can sometimes take a few growing seasons to get the level back down to normal, if you aren't careful.

I still need to till the greenhouse.  Hope to get that done this weekend.

The How to Grow a Giant Pumpkin Video that Works

 Got this nice note from a grower over the weekend.  Really glad to see that a video that touts how to grow over 1,000 pounds and you see some tremendous results from it.  The video is over an hour long and basically pulls from my last 10 years of growing experience.

From a happy grower:

"My second year personal best came in at ten place with a weight of 1204.5 lbs thanks for your videos on YouTube how to grow giant pumpkin 101 over 1000. Lbs thx again"