Nature is sometimes gentle, sometimes harsh. Without a doubt, Mother Nature will have her way in our vegetable gardens. Mother Nature’s way with pollination does not assure success each and every time. Rather, plant pollination problems can, and often do arise.
Most of us take the pollination process for granted. Out of necessity, experienced gardeners learn the ins and outs of pollination. Ultimately, they learn to identify the cause of plant pollination problems, so they can affect a correction or cure.
Identification of the problem is vital to implementing a solution. Sometimes the problem fixes itself over time. Sometimes, a plant pollination problem requires your intervention and corrective actions, to turn a potential disaster into a great crop!
The blossoms of some plants are self-pollinating. There are separate and distinct male and female flowers Good examples are tomatoes and beans. Other plants have uniquely distinct male and female flowers. Good examples are pumpkins, squash, and watermelon. Regardless of the type of flower, the pollen needs to get to and pollinate, the fruit to cause it to develop and grow.
There are three common plant pollination problems in the vegetable garden. Let’s explore the causes and the cures, so you can have a successful and productive garden.
Temperature Cold weather can delay the development of blossoms. Hot weather, on the other hand, can also delay blooms or cause them to shrivel and not produce fruit.
The Cure: Await milder temperatures. As soon as the weather improves, new blooms will appear. In cold temperatures, windbreaks, cloches, mini-greenhouses, and row covers will help
No female blossoms 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 Cure: 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, it did not occur properly, or plant stress caused the fruit to abort.
High Temperatures– As temperatures reach the high 80’s, the success rate for pollination declines. A heatwave in the nineties will result in poor if any, pollination. This is common with many plants, especially with more southerly climates.
The Cure: Wait for a cool spell and nature will do its thing. Shade covers in hotter regions are a big help. Avid giant pumpkin growers have resorted to building a small tent with ice or dry ice inside to lower temperatures around the fruit! This will work on other fruits and vegetables, too.
Lack of Pollinators: A disease affecting honeybees has devastated their population in many areas. Many other insects step in and inadvertently do the job….sometimes. Some are harmful insects, some are harmless. Many new growers will spray insecticides on their plants to eliminate the many unwanted and sometimes harmful insects. The spray kills insects and pollinators alike. The result…..no pollination. Been there…done that.
The Cure: Buy honeybee colonies. Do not spray insecticides during the pollination period. If you do spray during this period, you can always 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. That stress is caused by:
Water Too little or too much water.
The Cure: Keep soil consistently moist, not wet and not dry.
Soil pH imbalance pH levels are too high, or too low.
The Cure: Get your soil tested. Alter pH levels as indicated by the test.
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 can delay the flower/fruit stage. During pollination, phosphorus will promote flowering and fruit set. A range of micro-nutrients is also important.
The Cure: 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 micro-nutrients, many don’t.
Insect or disease problems – The plant is struggling to fight off damage from insects or disease. It will focus on survival rather than reproduction. It will not produce flowers and can abort existing fruit.
The Cure: 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. Organic gardeners, there are organic sprays.