How do you preserve a real pumpkin for the outdoor season?

Jam, one thing you can try is cleaning the outside with soap and water, keeping it very dry, and not cutting into it. If your weather is cool by then, and the pumpkin stays dry, it will last longer. If you could possibly get a freshly cut pumpkin, it will last longer than most grocery store pumpkins. Spraying the outside with polyurethane gloss should help, too. When all is said and done, a pumpkin is organic and thus, must die. You just need it to last until about December 1. Best wishes! ☺️

Try varnish the outside of it

After your pumpkin has been carved, rinse it out with water to get rid of excess strings and gunk.Take a large bucket or tub and fill it with three gallons of water.Stir three teaspoons of bleach into the water.Dunk in the pumpkin. Be sure to hold it down as it will try to float. The entire pumpkin should sit in the solution for two minutes. You might want to wear gloves, too.Remove from the solution and let the pumpkin air dry.

https://food-hacks.wonderhowto.com/how-to/prevent-carved-uncarved-pumpkins-from-rotting-0158208/

The best that I know of is to cut off the top clean out the innards , then soak in water and bleach for 15 minutes. I saw this on tv a couple of years ago when they were carving hundreds of pumpkin s

You might also consider decorating the pumpkin without carving into it... they last a long time that way. You could paint it or glue decorative items to the surface.