- Around the last week of June, your plantís main vine should be 8í to 10í long and growing fast. Pumpkins produce both male and female flowers, males having longer stems and females having a shorter stem with a bulb or baby pumpkin under the blossom. The males will be the first to show and will be followed by the appearance of females a week or so after. Once the males start showing, they will come fast and furious for the next month or so. This is the signal that the time is near to pollinate. The ideal position to set a pumpkin is at least 10 feet from the stump along the main vine. When each female first appears, try to make a small outward curve in your vine 2 feet either side of the female so that the female or baby pumpkin is on the outside of this curve. This is to prevent stem stress later on as your fruit grows to huge sizes and can actually press on the vine and pop your fruit off, ruining your season. Make the curve slowly and carefully over the course of a few days so as to not snap the vine.
To preserve the genetics of your pumpkin and to increase your odds of a successful fruit set, you need to hand pollinate your female flowers. When the female is ready to open, the blossom will be about 3 inches long and get an orange hue. The same goes for the male flowers. This means the flower will open the next morning and precautions need to be taken. First insure you will have 3 male flowers available for the next morning. The evening before, take a gallon zip lock bag and carefully cover the female and the 3 males, sealing the bottom to the stem. Try to inflate the bag so the petals donít touch the plastic. Tie-wraps placed gently around the top of each blossom works well also. Early the next morning, between 6 and 8am the flowers will open. Have a piece of yarn about 8" long with you, youíll need it later. Cut the males off the plant first, keeping them covered and watching out for aggressive bees. One by one remove the bag or tie-wrap from the males and carefully peel away the petals to the stem, trying not to jar or shake the flower as you do. You will see the stamen left on the stem, covered in pollen. Donít touch them or rub them on anything. Go to your covered female after it opens and carefully remove the bag or tie-wrap. Using the 3 males as a paintbrush, one at a time, carefully Ďpaintí and roll the pollen from the males over the segments in the center of the female flower, making sure the pollen covers as much of the segments as you can. Next, gently pull the petals of the female back up together, closing it off like it was before it opened and tie it closed with the yarn.
Congratulations, you just hand pollinated your first pumpkin.
If this sounds like a lot of work, it is. The prime time to set your fruit is between July 1 and July 10. This provides the right amount of time for your fruit to grow and be ready for Oct when most weigh-offs occur. If you only have one plant and are not concerned about preserving the lineage of your pumpkins genetic line for later seed distribution, you can let the bees do the work for you. However if youíre after a big one and want to do all you can to insure a good fruit set, itís imperative to properly pollinate by hand.
- Once you set a fruit on your plant, your not out of the woods yet. Many times a newly set fruit will abort due to high heat, wet conditions or poor pollination. The best approach is to follow the pollination procedure above for every female that forms on your plant. If the temperature is in the high 80ís or above, place frozen soda bottles of water next to the new set to keep the immediate temperature down, provide some sort of shade for the new fruit and adjust your watering by the amount of rain that falls during these the 2 weeks following pollination.
Observe the new pumpkins on the vine for 10 days after they have been pollinated. Note the shape, growth rate and skin texture as gauges for which one will be your main fruit. A good measure of growth rate is a 30" circumference at 10 days old. The skin of your fruit should be yellow, shiny and tender. One other aspect to take into account is stem length and position in relation to the vine. Your main candidate should be a fruit that has a long stem and is oriented as close to perpendicular to the vine as you can get. If all your fruit are at an angle of less than 90 degrees to the vine, choose the one that is closest to perpendicular to the main vine. You will be able to move the fruit very slowly up to Ĺ" a day toward 90 degrees. This will reduce stem stress when the fruit really starts packing on the pounds. Use extreme caution when moving your pumpkin, it doesnít take a lot to crack or snap off the stem.
- By August 1, you should cull your fruit down to the one fruit on each plant that shows the most promise, taking into account the items listed above.