Pumpkin Pollination & Genetics

I received a request to write about how to choose what plants to cross and how to develop genetics in your seeds that could potentially grow a world record pumpkin the following season.  I should start by clearing a commonly misunderstood part of pollination.  That is that the pollination you do in the next few weeks will have no effect genetically this season on your pumpkin.  Some think that by pollinating with a particular plant this season might effect how the pumpkin grows this season.  That isn't the case.  The pumpkin isn't the child in the pollination.  It is the seeds in the pumpkin that are the children, so the pollination you do this year will only effect next year's pumpkins.

First, lets talk about how to properly pollinate your female flower so you can keep the genetics pure.  Nature has wonderful pollinators that can do a great job of pollination for you.  Bees and other insects will find open flowers in an instant and most of the time a female flower will get pollinated with little help from us.  However, bees will pollinate with the pollen they have come in contact with and in some cases it won't be the pollen you want.

An Atlantic Giant pumpkin is a Cucurbita Maxima variety but so is a banana squash, so letting the bees do the pollination means that your pumpkin plant the following season, from the seeds this season, might give you a surprise if you don't control the pollination.

What I do to control the pollinations is to cover my female flowers with a little mesh bag the evening  before they open.  You can tell when they are going to open because the flower peddles become more orange and the flower tends to elongate some the day before.  The evening before I find some male flowers (ideally 3-4 but one will work) that I cut off and put in water.  The next morning, around 7:00am I'll take those male flowers and hand pollinate the female flower.  I then cover that female flower with the same mesh bag to make sure bees don't get into the flower over the next hour.  Doing it this way I ensure that both the male flowers and female flowers only have the pollen in them that I want them to have.

Choosing which plants to cross can best be summed up in a Forest Gumps quote, "Life is like a box of chocolates.  You never know what you are going to get inside."  Genetics are a funny thing.  Just like in real life, you sometimes have those those short round parents who produce a gorgeous, tall and skinny daughter.  There are world record pumpkins who have produced very small progeny (I think of the 1385 Daletas as an example).   Sometimes the best planned crosses just don't work out.

What I look at when making crosses is the pedigree of both plants.  If you go to tools.pumpkinfantic.com you can search most any seed and look up who mama and papa was for generations.  Typically when doing crosses you either want to bring in a pollinator that is very similar or very different.  So finding a pollinator with the same mama and papa or something that has very little heritage that is the same seems to work out best.

Next I like to look at the shape and ribbing of both parent's pumpkins.  Ideally you don't want a pumpkin that is very ribby.  Ribs can cause splits in your pumpkin because when a deep rib intersects a crack on the inside of the pumpkin, you then have a hole and your season is done at that point.

Next, I like to take a look at the vigor and characteristics of my plants.  If I have a plant that isn't an overly aggressive grower than crossing it with something that seems to be more aggressive might be a good idea.  If I have a plant with big leaves I may not want to cross it with a plant that also has overly big leaves because I found that really big leaves tend not to be as good a shape at the end of the season as wind blows them over.

Lastly, I look at similar crosses that other people have made and see how they tend to work out.  You would think that a 1725 Harp and a 1161 Rodonis, which have both produced world record pumpkins, would be a great cross but in the research I did on other crosses found no great progeny.  This doesn't mean that it couldn't work, but those genetics didn't seem to mesh as well as you would have thought.

Most of the recent world record pumpkins have come from the 2009 Wallace seed.  You look at it's pedigree and you see a cross of two plants that have very little parentage in common.  Obviously that worked.  You then look at the 1725 Harp seed that produced the 2009 pumpkin and it was a selfed pumpkin.  That means the male flowers that pollinated it came from the same plant.   That cross obviously worked as well.

More growers should probably self pollinate their plants.  That practice was kind of frowned upon just 5 years ago until the 1725 Harp started busting out really big and one ton pumpkins.  Selfing can homogenize pumpkin traits and enhance them.  So if you have an exceptional pumpkin plant that produces a really big pumpkin than the seeds from that selfed pumpkin could have some seeds that aren't as good as the parent genetically but it could have seeds that have some of the same traits that have been enhanced.  If enough seeds are grown from that selfed pumpkin that are then selfed the same should happen in the next generation were you can get some super seeds that take the genetics to the next level up.  Problem with pumpkin growing is that you need a lot of growers to grow your seeds in order for that to happen properly, but that is how the seed companies do it to lock in traits and get desirable genetic lines.

This season my plan is to pollinate my 1985 Miller plant with my 282 Scherber plant.  This is one of those crosses where I am bringing in similar genetic lines into that cross.  Haven't decided what I'm going to cross the 282 yet, but I'll be deciding that at the end of this week.

A word of warning.  Many times the best laid pollination plans don't work out.  Lots of times I've planned on pollinating with a particular plant and there were just no male flowers on it that were ready on the day of pollination.   Sometimes you pollinate, get a perfect pumpkin and then there are no seeds or the seeds aren't viable in the pumpkin.  When my big 1421 pumpkin went down I did a couple of late pollination on that plant using pollen from the clone of the 1725 Harp plant that produced the world record 2009 pumpkin.  I would have grown that seed in a second.  It was an ideal cross.  After a semi-early frost I opened up the pumpkins and there was lots of seeds but the seeds weren't mature so none of the seeds would grow.

Happy pollinating to everyone!  Things get exciting in the pumpkin patch this time of year.  Hopefully, in about 30 days from now we will all be talking about how our pumpkins are putting on 35-40 pounds a day.

If you have something you would like for me to write about feel free to post a comment and I would be happy to write about the subject or reply to you comment in the comment fields below.