NDSU Extension - Burke County


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Pruning or Stepping Over Potato Plants

County Agent News
Dan Folske
June 29, 2020 

Pruning or Stepping Over Potato Plants

            A common question I get every year is “when I should step over potato plants or cut the tops off”. Many people seem to think they need to do this to force the plant to produce larger potatoes. While pruning the blossoms off the plant may prevent the plant from wasting energy on seed production, I cannot find any research to indicate that it would be a measurable difference. However, if you have children helping you in the garden you may want to pick the blossoms to prevent the tomato like seed pods from forming because they can be poisonous if eaten.

Lindsey Miller, 2020 Miss Rodeo North Dakota Winter Show Queen is a Burke County 4-Her studying Agriculture Education at Dickinson State University. As part of her coursework she is interning with the Burke County Weed Board and volunteering with the NDSU Extension office in Burke County. I asked her to look for information regarding the effects of pruning potatoes and write an article about what she found. Here is her article:

If you have potato plants with a lot of foliage, you should trim them, right? Actually, you maybe should not. There seems to be a common thought that trimming your potato plants or stepping over them will make them put more energy into growing larger potatoes. Some people believe that by trimming the foliage the potatoes will grow larger since their energy will not be focused on the stalks of the plant. However, it is actually the opposite case. When you cut a potato plant, you are stopping the growth in its entirety. After a potato plant is pruned, it focuses on regenerating what has been lost, drawing the energy away from the actual potatoes. With all the energy focused on growing back the missing foliage, the potatoes are left at the same size as prior to the plants pruning. This practice came about when large potato farmers were contracted to grow a specific size potato and wanted the potato skins to harden up before harvest or needed to harvest on a specific date. A great example of this was an experiment done by a gentleman of the name Max Bee from Tasmania, Australia in 2016. He planted two different sections of 10 King Edward potatoes at a 15 centimeter depth. Throughout the summer, both of the sections received the same amounts of water and sunlight, making the data very accurate. Around early summer, Max trimmed the one section of the plants about halfway down. Once harvest came around, he compared each potato crop. The results included 4.2 kilograms from the pruned plants and 5.8 kilograms from the unpruned plants. Besides the weight of potatoes collected being vastly different, the sizes of the potatoes were as well. It was also mentioned that the potatoes that were not pruned came out larger and with a larger combined weight. So, there you have it, trimming your potato plants does not necessarily make them bigger. However, if you would like to control the size of your potatoes, trim the plants when the potatoes have reached your desired size. Also, stepping over or pruning the plants approximately two weeks prior to the designated harvest time can be beneficial as well. Stepping over or pruning will allow the potato skins to harden allowing for less damage to the skin upon harvesting.



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