One month from tomorrow many growers in Colorado will be cutting their pumpkin off the vine. My family throws our biggest party of the year on that day. I do it to celebrate the growing season and my wife I believe does it to celebrate the end of the growing season. For these next 30 days however I'm going to try to put on as much weight as I can on the pumpkin. As I've mentioned before I haven't had good luck in September for putting on the pounds. My 1161 Rodonis, which tends to have longer growing genetics, did fairly well two years ago but I've never had great weight gains in September. In this post I'm going to tell you what I know from my own experience and from other people's experiences what to do and what not to do.
First off, don't give up. Jim "The Biz" Grande learned that his rookie season and he shared that with me. He was ready to pull his plant out of the ground but decided to keep at it and late in the season his pumpkin took off and he ended up taking 3rd place. You never know what these pumpkins will do.
Second, keep your watering program going. As the weather gets cooler you may need to cut the watering back some, but don't let the soil dry out. Your tape measure may not say that pumpkin is growing much but when the pumpkin is this big even an inch of growth is a lot of pounds so you need to keep the water available to keep the pumpkin growing. You also don't want to let the pumpkin dehydrate. A pumpkin is 80% water so keeping the pumpkin hydrated means a lot of weight on the scale.
Maybe a little extra potassium late in the season, but don't over do it. A number of growers have tried to dump a bunch of fertilizer on a plant to get extra pounds and what some growers will tell you is that the pumpkin stopped growing after they did that or it slowed down. I usually use some liquid seaweed (0-0-1) with some humic acid once a week for the last four weeks.
Check the stump and stem of the pumpkins along with the main vine to make sure there isn't any rot. If you can catch that kind of stuff early and treat it you'll be fine but if it is left alone you'll lose weight or the entire pumpkin in no time.
Enjoy it! September is the best time of the whole year. I see growers bring a pumpkin to a weigh-off and say "it isn't very big," but big is relative. I showed a visitor my kids' pumpkin the other day and it was the biggest fruit they had ever seen. Everyone loves a big pumpkin and to most people 100 pounds is a very big pumpkin. Enjoy what you've got and start planning and prepping now for next year!