The most commonly asked questions during late June thru early August, are related to pumpkin pollination. Or, should we say….lack of pollination. The FAQs below will help you to identify and eliminate the most common problems.
The pollination period is an anxious time, perhaps the most anxious time of the entire pumpkin growing season. After all, this is when the fruit that will adorn your front porch this fall begin to develop. First, let me suggest you relax and not worry so much. Pollination problems are all too common. Fortunately, they are usually remedied once the cause is identified and eliminated. And, the season is long. A healthy pumpkin plant will produce many fruit all season long. If at first the vine does not succeed, it tries, tries again.
Males usually come to the party first. (do you remember those days?) They come in big numbers and strut their stuff, awaiting the arrival of the ladies. After a while, sometimes several days or more, a few timid females begin to arrive. Usually there is no problem here, just an anxious grower. See pictures of Male and Female flowers.
The “Fix”: A little more patience. A little extra phosphorous will help promote blooms. Hold off on Nitrogen during the pollination period.
Also see plant stress below.
Pollination did not occur, did not occur properly, or plant stress caused plants to abort fruit.
High Temperatures– As temperatures reach the high 80’s, the success rate for pollination declines. A heat wave in the nineties, will result in poor if any, pollination.
The “Fix”: Wait for a cool spell and nature will do it’s thing. Avid pumpkin growers resort to shade covers, and even building a small tent over the fruit with ice or dry ice inside, to lower temperatures around the fruit!
Lack of Pollinators: Many new growers spray insecticides on their plants, to eliminate the many harmful insects. The spray kills insects and pollinators alike. The result…..no pollination. Been there…done that.
The “Fix”: Do not spray during the pollination period. If you do spray during this time period, you may need to hand pollinate.
In nature when a plant is under stress, it will not produce fruit or it will abort existing fruit. It is a survival mechanism, allowing a plant to focus upon survival first. Plant stress is caused by:
Water Too little or too much water.
The “Fix”: Keep soil consistently moist, not wet and not dry.
Soil pH imbalance pH levels are too high, or too low.
The “Fix”: Get your soil tested. Alter pH levels as indicated by the test. This one takes time to fix.
Mineral and/or Nutrients Levels too high, or too low. Nitrogen is important in early plant growth and throughout the season. Too much nitrogen will cause lots of green leaves and growth, but few if any fruit. During pollination, phosphorus will promote flowering and fruit set. An ample supply of essential micronutrients are also important.
The “Fix”: Get your soil tested. Alter levels as indicated by the test. Cut back or halt nitrogen applications for a while. Add phosphorus. Look for fertilizers that contain micronutrients, many don’t.
Insect or disease problems The plant is struggling to fight off damage from insects or disease. It will focus upon survival rather than reproduction. It will not produce flowers, and may even abort existing fruit.
The “Fix”: Apply insecticides and/or fungicides as appropriate. Trim and remove affected leaves and vines to promote new, healthy growth. New growth will produce new flowers and fruit.