Estimating Maturity and Harvest Readiness in Sweet Corn

Sweet corn, a popular summer staple, requires precise timing to ensure optimal sweetness and tenderness. Knowing when to harvest is crucial for enjoying the best flavor and texture. Here’s a guide on how to estimate the maturity of sweet corn and determine the perfect time for harvest.

Estimating Maturity

Days to Relative Maturity:

 Sweet corn varieties have a range of days to maturity, typically between 60 to 100 days from planting. Check the seed packet for the specific variety’s estimated days to maturity and mark the planting date on your calendar.

Silk Emergence:

Depending on temperature, corn maturity can deviate from the relative days to maturity and one of the most reliable indicators of sweet corn maturity is the emergence of silks from the ear. Generally, corn is ready for harvest about 19 to 23 days after the silks appear.

Kernel Development:

To estimate maturity, gently peel back the husk to expose a few kernels. They should be plump and in tight rows. The kernels will transition from a milky white to a more translucent yellow as they mature. When punctured, the liquid from the kernel should be milky, not clear or doughy.

Feel of the Ear:

A mature ear of sweet corn will feel full and firm when you squeeze it. The tip of the ear should be filled out with no gaps between the kernels.

Determining Harvest Readiness

Silk Color and Texture:

The silks should be brown and dry when the corn is ready to harvest. Green or wet silks indicate that the corn is not yet mature.

Ear Size and Shape:

Fully mature ears will be of the size typical for the variety and will have a rounded, blunt end. Immature ears may still appear pointed at the tip.

Kernel Milk Stage:

Perform the “thumbnail test” by puncturing a kernel with your thumbnail. If a milky liquid exudes, the corn is at the peak of sweetness and ready for harvest. If the liquid is clear, it needs more time. If it’s thick and doughy, the corn is past its prime.

Timing of Harvest:

Harvest in the morning when the temperatures are cooler to maintain the sweetness and prevent the sugar from converting to starch. Sweet corn sugars begin converting to starch soon after harvest, so it’s best to consume or process the corn as soon as possible. Note: if you are growing a sh2 variety, there is more flexibility in harvest timing and shelf life once harvested.

Additional Tips

Successive Plantings:

To ensure a continuous supply of sweet corn throughout the growing season, consider planting successive crops every one to two weeks. This practice, known as succession planting, will provide fresh corn over a more extended period.

Handling and Storage:

After harvesting, refrigerate the ears immediately if not consuming them right away. Keeping the sweet corn refrigerated will help retain its sweetness and quality for one to two weeks.

By following these guidelines, you can ensure that your sweet corn is harvested at the peak of its flavor and texture, providing a delightful addition to your summer meals. Happy harvesting!

About the Author

Eric Brucker      Sweet Corn Breeder

Eric has worked for IFSI for 11 years, starting out as an assistant breeder before being promoted to a Station Manager, and now a sweet corn breeder. He earned his degrees from the University of Illinois with a B.S. in crop biotechnology and an M.S. in plant breeding and genetics. His interest in sweet corn started as a kid selling the variety Honey ‘N Pearl out of the back of an old truck. Eric’s enthusiasm for sweet corn and sweet corn promotion is evident by the way he interacts with people. He is always happy to talk about the new varieties and how they were developed by the IFSI Team. And many days in the later summer, after a hard day of work picking and evaluating sweet corn, you will find Eric picking more corn to give away to any friend or stranger who will eat it.