Growth Stages of Sweet Corn

Sweet corn goes through a very specific process of growth, beginning with vegetative growth, known as the 'V' stages, and completing with reproduction, referred to as the 'R' stages. Each stage is critical to the proper development of the plant and the formation of the corn itself; proper care during each stage can help optimize production.

VE Germination and Emergence

This stage covers the initial germination of the seed and emergence of the plant. The sprout, referred to as the mesocotyl, reaches the surface of the soil and is exposed to the sun. A coleoptile will grow from the mesocotyl. This will eventually grow into the stalk of the corn plant. A root, called the radicle, also begins to emerge, working its way out into the soil.

V1-V(n) Vegetative Growth

About a week after the coleoptile emerges, the root system continues its growth. At each stage, referred to as V1, V2, V3, through V(n), which is the last stage and can be a different number depending on the cultivar, a new leaf collar and leaves will form as the stalk grows. The coleoptile will also send out nodal roots that will help to anchor the plant in the soil. During these steps, the corn plant will grow to its full height and reach vegetative maturity. This can be from four to eight feet tall, depending on the variety of sweet corn.

During the later steps of this stage, when the plant is almost at full height, immature corn husks will begin to grow on the stalk of the plant. The corn cob will form, producing kernel rows. The plant also begins to form the silks that will eventually emerge in the reproductive phase.

VT Tassel Emergence

In the VT stage, the male reproductive portion of the plant, the tassel, will emerge. The tassel produces the pollen required for fertilization. This stage begins about two to three days before silk emergence to ensure that there is pollen available to fertilize the plant. Pollen is usually shed in the mornings and evenings.

R1 Silking

The R1 stage represents the beginning of the reproductive phase of sweet corn plants and usually occurs for 55 to 60 days after emergence. Silks, the thin thread-like female reproductive organs, emerge from the tip of each corn husk. Each silk leads into the husk. The tassels will begin to shed their pollen, which will fall onto the silks, fertilizing each one. The sperm within the pollen will travel down the silk to fertilize each kernel of the corn plant. This stage usually lasts less than a week.

R2 Blister

During the R2 stage, the silks darken and dry out. Each kernel is white and looks like a little blister on the cob, which is now nearing full size. The kernel will continue to develop during this stage. Starch begins to accumulate in each kernel.

R3 Milk

The R3 stage is referred to as milk because the starch forming in the kernels is white and watery, thus resembling milk when released from the kernel. The endosperm of the kernel, the part that will eventually grow into another corn plant, is now fully developed.

R4 Dough

About a week after the R3 stage, the R4 stage takes place. In this stage, the starch in the kernels begins to solidify into a doughy consistency. This is due to the increased accumulation of starch and the decrease in water in each kernel. At the end of this stage, sweet corn for fresh consumption is usually harvested.

R5 Dent

If the sweet corn is to go completely dry for seed corn, it will be left on the stalk through the remaining phases of the corn plant's growth process. A dent or dimple will form in the end of each kernel as it dries out. Drying kernels will also show a white layer inside the top of the kernel.

R6 Physiological Maturity

At this point the kernels are completely mature and are capable of producing a new corn plant. A black or brown layer forms where the kernel is attached to the corn cob. The vegetative portion of the plant will die back. The moisture in the corn kernels will have dropped to around 20 to 30 percent moisture, depending on the variety and growing conditions.