The AgriPost
July 31, 2026
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Standing Water Leaves Lasting Questions for Corn, Sunflowers and Flax
By Harry Siemens
As floodwaters continue to recede across much of Manitoba, many producers are getting their first clear look at what weeks of saturated soils have left behind. While some fields are beginning to recover, others are showing lasting signs of stress that could affect yields for the rest of the growing season. Morgan Cott, Agronomy Extension Specialist – Special Crops with Manitoba Crop Alliance, says the real damage from prolonged flooding often occurs below the soil surface. “The crops we grow and work with in Manitoba do not generally do well during extended periods of flooding or saturated soils,” Cott said. “Roots and growing points need oxygen to develop, so plant growth is delayed under these conditions.” Without oxygen, roots stop growing efficiently, nutrient uptake is reduced, and plants
Standing water surrounds a Manitoba corn field after heavy rains saturated soils across the province. Manitoba Crop Alliance says young corn is especially vulnerable when flooding covers the growing point, restricting oxygen and slowing root development. Photos by Eric Tyschinski, Manitoba Crop Alliance
use valuable energy simply to survive. Even after standing water disappears, weakened root systems can continue to limit crop performance. Corn has been one of the more vulnerable crops where flooding persisted during early development. Cott said corn at the V5 stage or smaller faces the greatest risk because the growing point
remains below ground until approximately the V6 stage. “If the growing point is below the waterline, conditions become anaerobic and it cannot breathe,” she said. Although leaves above the water may continue photosynthesis, flooded roots cannot supply the nutrients and moisture needed for normal growth.
Now that many fields are drying, Cott said growers should look for renewed leaf development and healthy plant colour to determine whether the crop is recovering. Sunflowers face similar challenges. Although they use large amounts of water later in the season, saturated soils quickly deprive their roots of oxygen.
Cott said sunflower plants should not remain in standing water for more than about three days if growers hope to minimize yield loss. As soils dry, another concern begins to emerge. High humidity following flooding creates ideal conditions for sclerotinia, one of the most damaging diseases affecting Manitoba sunflower production. Growers should continue monitoring fields for healthy new growth while watching carefully for disease development as the season progresses. Flax has even less tolerance for prolonged flooding. Cott said flax can survive only about three days in standing water before significant yield losses begin to occur. While flax is generally less susceptible to some root diseases than other crops, its ability to recover from extended flooding remains limited. Across all three crops, Cott
recommends producers continue evaluating root health as fields become accessible. Digging up plants provides one of the best indicators of recovery. Healthy roots should remain firm and light-coloured, while dark or deteriorating roots often signal lasting stress. Saturated soils also discourage deep root development, potentially leaving crops more vulnerable if hot, dry weather develops later this summer. The full impact of this year’s flooding will not be measured simply by the number of acres lost underwater. In many fields, the lasting effects will be determined by how well weakened crops recover through the remainder of the growing season. As Manitoba producers move into July, careful scouting will help identify which fields are rebounding and which may continue to pay the price for weeks of excess moisture.