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San Diego

My pumpkins have always developed a concave area on the part of the fruit that rests on the soil. Three quarters of the pumpkin look round and great, but when I harvest and flip the pumpkin over the side that had rested on the soil is either flat or actually indented. I see plenty of giant pumpkins with one flat side in pictures, but those are thousand pounders and my largest was 550 lbs. Is there one factor that tends to cause this growth pattern - genetics, soil, nutrients, watering, heat, etc. - or could it be one or a combination of all of these things? I should mention too that I am forced to grow on a relatively small plot; maybe this is a leaf area thing? Thanks for any input, hope 2013 is good to everyone!

1/30/2013 12:36:56 AM

Dorval,Quebec

Hopefully I'm understanding your question...My situation is similar to yours.....I'm thinking it's mainly due to fast growth and a natural way for the fruit to be structurally strong(strong base).If mine are concave I'm thinking it's due to weight on the sides compared to the center of fruit,more pressure on the sand causing some compression,maybe damp sand that dosen't allow the bottom of the fruit to slide out as easy in growth.I used to be disappointed seeing a concave bottom,thinking I would miss some weight(at 500 lbs,every pound counts,lol) but a posting months ago on the subject had some opinions to the opposite...more surface area,less cavity space.

1/30/2013 1:08:02 AM

Gays Mills, Wisconsin

Good info Mike.
Kevin, some growers use a mill fabric, sand, plywood etc.. below the pumpkin to provide the fruit's growth to "slide" outwards as it grows to help create a flat (less concaved) bottom.
As the pumpkin gets heavy it'll sink in soft soil which lessens "sliding" and may be the cause of some concaving.

1/30/2013 7:56:05 AM

43.841677 , -79.086692

I put sand down, then mill fab then a dusting of sand on the top of mill fab to act as a bearing surface to help the fruit slide as it grows. Still, you can never prevent the pumpkin from heaving up 100%. I don't think it costs you on the scale either way.

1/30/2013 9:43:52 AM

Upa Creek, MO

Kevin, I grow to about the size you have and use Chris' method above with sand and mill fabric. All 4 of my Ag's over the last 2 years have had flat bottoms.

1/30/2013 9:50:42 AM

Garden State Pumpkins

watch the pumpkin this year. If you are in extremely soft soil the pumpkin will compress the soil right below it first as it puts on weight. the small pumpkin will lay down in a uniform shape (round) ie. the first three hundred pounds will compress that soil a relatively large area to the final pumpkin weight. the next three hundred pounds will expand out from there 3 more inches. I will not be able to raise the pumpkin off that spot giving you that "turtle shell" on the bottom. I had this problem alot in a 20% om soft leaf soil. Harder soil will give you a flat bottom as the expansion will allow the sides to lift the center more. When i switched patches to the harder surface i got flat bottoms. GrowEmBig! chuck

1/30/2013 6:04:26 PM

San Diego

Thanks for the great tips and info everyone! I have been using sand under my pumpkins, but not mill fabric or plywood, but now I think I will start using one or the other. Good to know that the concaving and flattening are probably not costing on the scale.

2/3/2013 11:41:57 PM