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"

 

The Pumpkin is Coming Down the Stretch!

Pumpkin Gordo Gato

Five weeks from today will be the first giant pumpkin weigh-off of the year.  My pumpkin is currently 77 days old.  So I've probably got 14 to 20 days of growing left in her.  Weather has been hot lately, but that isn't bad for me.  The cold of night from this point on is my greatest potential issue.  Nighttime lows have stuck around the low 50s and high 40s, which is not close to ideal, but not bad this time of year for me.  If we can keep it from getting into the low 40s over the next 20 days, we may be able to get to get 20 days of growth or more.  She is slowing down however right now.

Anything less than 1,000 pounds is unacceptable to me.  That should be the minimum.  This pumpkin still has a descent shot at 1,000, but it will be close.  Low 900's is what I would estimate if she slows down quickly and only goes the 14 days.  Over 1,000 would be the estimate if it grows the full 34 remaining days, but I don't see that happening.  This pumpkin looks meaty like last year's so the hope is still that it can go heavy to the charts.

1325 Johnson (aka Gordo Gato) Pumpkin Pic

About two weeks ago I came to the conclusion that if this pumpkin was going to get into the acceptable range it would have to meet a certain level of growth over the next two weeks.  In two days we will hit that 14 day mark.  The target was an average growth of 18 pounds a day.  As of Saturday it was at 17.6 pounds per day, so close.  This pumpkin is going to need to grow for 99 days in order to meet that final goal and there is a lot of time left, so we will just have to see what happens.

This pumpkin is looking just about as meaty as the 2005 Haist from last year (pictured below).  The 1325 is a seed from the 2005.  Some notes.  2005 Haist had much taller leaves and was pollinated two weeks later, so the pics are a little deceptive in terms of the size of the pumpkin.  The 2005 had beautiful leaves at the end of July.  This plant's leaves are looking pretty old already on the first half of the plant. The 2005 stopped growing mid-September because of cold.  If this 1325 can be a long grower and the weather is a little kind in September it has a chance to get to descent size, but I would be really surprised if it could match last years.  Maybe if it goes 30% heavy.  I don't plan on that, but I would give it a descent chance of going heavy.

1325 Johnson on 8/3/20

2005 Haist 2019 on 8/26/19

Keeping in Cool When Things are Hot in the Pumpkin Patch

Forecast here is for 5 days of 100 degrees.  That is very hot for Midway.  We usually don't see those temps at all in a year.  I often hear from growers, especially new growers that they are seeing issues with their leaves flagging.  That is a clear sign that either you are under watering or the leaves could use some misting during the heat of the day.  When I was in Denver, I had a hose end timer that was attached to a sprayer that went out about 25 feet and it was set to go off about every 20 minutes.  That worked nicely.

In the greenhouses I have some foggers set to go off about every 15 minutes during the heat of the day.  I like these foggers because the mist is very fine.  You could walk through it, feel cool, but not wet.  To much moisture could increase disease pressure so with the foggers running every 15 minutes the leaves have enough time to dry off between mistings but at the same time not enough to heat up.  I see almost no leaf burn with this setup.

Yesterday I added shade cloth to the greenhouse.  22% shade cloth will add additional shade to help keep the greenhouse a little cooler.

Gordo Gato Pumpkin Report

The pumpkin keeps growing, but not at any incredible rate.  Still signs that this one could flatten out the growth curve and if it does that we will be okay, but if it takes a regular growth curve and isn't a long grower, the pumpkin will be small this year.  Not overly optimistic.

The leaves right now look like my leaves did in mid-August of last year.  Not happy.  I did some checking today and there are early signs of spider mites.  I found an aphid on the pumpkin but didn't see any others, so I sprayed everything.  Added a fungicide into the mix.  I'll need to be diligent on the fungicides this year, because with the leaves in a weaken state they will be more susceptible.  Daconil and a TKO will be my go to powdery mildew killers along with some silica to help prevent spread.

Not thinking this will be my year.  It is taboo to say this, but it is the one hope that I've got.  The seed this pumpkin came from was a pumpkin that went 8% heavy.  This pumpkin has the same shape.  The pollinator I lost the pumpkin on early, but the 2255 progeny all went heavy except for one and many went big heavy.  The 2005 progeny that the seed came from all went heavy and some of those went big heavy.  This pumpkin thumps nicely.

This is the Pumpkin Named Gordo Gato

I've named the 1325 pumpkin Gordo Gato, in honor of our cat named Fat Kitty who passed away earlier this year.  Gordo Gato is slugging along right now.  I'm hoping the issue is like last year and that the cold weather has hampered growth and it will decide to kick in late.  Last year's pumpkin at 30 days old was only about 220 pounds.  Which is terrible.  But then it made up ground late.  I'm hoping this one is the same (it is a seed from that same pumpkin).  The issue I have is that last year the pollination was 2 weeks later, so when the pumpkin was ready to start growing it was getting into better weather.  I fear I've burned two weeks of growth in bad weather that I might not be able to make up.  Hopefully this pumpkin decides to be a long grower.