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Ohio State University Extension


A Guide to Corn Growth and Development

Agriculture and Natural Resources
Osler Ortez, Corn and Emerging Crops, Department of Horticulture and Crop Science, The Ohio State University
Mark Licht, Extension Cropping Systems Specialist, Department of Agronomy Iowa State University

One of the critical activities in growing a crop is understanding and keeping track of its growth and development. Growth and development are terms often used interchangeably, yet each has a distinct meaning. Corn growth is related to the increase in size of an individual plant or plant component, and it is influenced by factors such as temperatures, water availability, fertility, stress, and plant competition. On the other hand, corn development relates to the plant’s progress in stages of maturity (e.g., moving from earlier to later stages). Temperatures (heat unit accumulation) primarily drive development, and it can be predicted (corn growing degree days, see how it works here) (Osler & Lindsey, 2023).

For example, two plants may each have five fully developed leaves and are developmentally the same; yet one plant may be shorter due to plant stress (e.g., lack of water), resulting in reduced growth. Frequently, when we refer to the status of a crop, development works as a better measure than growth.

A plant with determinate growth has vegetative structures (e.g., leaves and stalk) that are initiated before reproductive structures (e.g., tassel and ears). In corn, vegetative development ends when reproductive development begins. Because corn is a determinate plant, the ability to compensate for yield-limiting factors and/or stress is lower compared to indeterminate species such as soybeans in the northern United States which continue to produce vegetative growth throughout their crop cycle.

Corn yields are the result of plant biomass accumulation (the vegetative “source”) and allocation of plant biomass produced assimilates to the ear (the reproductive “sink”). Yield formation is determined by three main components. Each component is determined at different times during the growing season:

  • plant/ear number per unit of area (early in the season)
  • kernel number per ear (kernel rows per ear and kernels per row, midseason)
  • kernel weight (late in the season)

Vegetative and Reproductive Staging OverviewGraphic depicting growth of a cornstalk, with stages of development, from no cornstalk (left) to fully grown cornstalk at the end of its life cycle (right).

Given the spread of when plants form yield, understanding the crop’s cycle—including its vegetative and reproductive phases—is essential (Figure 1). Corn plants are first staged as vegetative (starting with emergence until tasseling) and then reproductive (starting with silking until physiological maturity). Vegetative and reproductive stages of development are determined when 50% or more of the plants reach a particular stage.

Among the practitioner community, different corn staging methods are available:

  1. Leaf collar method: most widely recognized method in the United States and recommended for practitioners.
  2. Horizontal leaf: used primarily by crop insurance adjustors, also known as “droopy” leaf.
  3. Leaf tip and BBCH scale: used at times by the international scientific community.
  4. Plant height: used on pesticide labels, often specifying the proper application timing of the product to the crop.

The most recognized staging method recommended by universities for practitioners in the United States is the leaf collar method for vegetative stages (V) and kernel development for reproductive stages (R), summarized in Table 1. The table shows that two vegetative stages, emergence (VE) and tasseling (VT), do not require counting leaves. The reproductive stages are designated with an “R” followed by the numbers one to six, depending on kernel development. Some of the technical descriptions and all figures used to illustrate the stages below are reproduced with permission from Abendroth et al. (2011).

Table 1 (click to download PDF). Key vegetative and reproductive stages for corn, from emergence (VE) to physiological maturity (R6). A brief description is included for each stage.
Table showing the different vegetative and reproductive stages for corn, from emergence to physiological maturity.

Emergence (VE)

Photo depicting seedling with small roots growing underground and a green shoot growing aboveground.

A plant is defined as VE when the coleoptile emerges through the soil surface (Figure 2). The root system consists of the radicle (with branch roots) and seminal roots. The number of calendar days between planting and emergence varies and is primarily related to soil temperature, soil moisture, planting depth, and seed-to-soil contact. Earlier planting dates in the Corn Belt often have cooler temperatures, leading to more days (up to 30 days) required for germination. When planted later, warmer temperatures are expected, and fewer days (about 6–8) to emergence are observed.

Vegetative Stage (V1)

Photo depicting seedling with three roots growing underground, one oval-shaped leaf growing from the base of an aboveground shoot, and two pointed-tip leaves growing above the oval-shaped leaf.

Plants with the first collared leaf are defined as V1 (Figure 3). The tip of the first leaf has an oval or rounded tip, which is different from all other pointed-tip leaves. This first oval-shaped leaf is the starting point for counting leaves using the leaf collar method. Leaves continue to be initiated at the growing point below the soil surface. The seminal root system is present, and one or two nodal roots may be visible.

Vegetative Stage 2 (V2)

Photo depicting seedling with five roots growing underground, and three pointed-tip leaves growing above an oval-shaped leaf at the base of the plant.

Plants with their first two collared leaves are defined as V2 (Figure 4). Leaf initiation continues, and nodal root system formation is started. The nodal root system (formed above the seed approximately ½ to ¾ inch below the soil surface) is identifiable apart from the seminal roots (forming on the seed).

Vegetative Stage 3 (V3)

Photo depicting plant with numerous roots growing underground, three leaves growing from the top of the aboveground stalk, and two smaller leaves growing from the base of the stalk.

Plants with their first three collared leaves are defined as V3 (Figure 5). At this stage, the nodal and seminal root systems are about the same size (in length and dry matter). Leaf initiation continues. Before V3 and continuing until V6, the plant is standing due to the strength of leaf sheaths layered on top of one another. The stalk remains below the surface at V3, although it is distinguishable with plant dissection.

Vegetative Stage 6 (V6)

Photo depicting plant with root system growing underground and long, pointed-end leaves growing from a stalk aboveground.

Plants with six collared leaves are defined as V6 (Figure 6). The lower leaves are more weathered, becoming increasingly more challenging to identify and count as they tear away from the expanding stalk and are senesced. All leaves are initiated by V6 but are too small to see without magnification. In a corn plant, each leaf originates from a stalk node (with internode tissue separating nodes). A minor amount of internode elongation begins before the V6 stage, with the majority occurring from this point forward (Figure 1). Due to internode elongation, the growing point transitions from below to above the soil surface at this stage. Damage to the emerged plant before V6 has the potential to regrow if the growing point is below ground. The nodal root system becomes dominant, with the root mass approximately one-third of the plant’s total biomass.

At the V6 stage, ear shoots are being initiated and grow along the stalk at various nodes. Ear shoots are first present at lower stalk nodes, initiated first, with upper ear shoots following. Although the primary ear shoot is not yet visible, it is initiated at or near the V6 stage; magnification is necessary to view it. The primary ear is typically found at nodes 12, 13, or 14.

The potential size of an ear is a function of the number of kernel rows around the ear and the number of kernels per row. Kernel rows have an even number because the initial rows divide, with each initial row forming two rows. Most hybrids grown in our region have 16 or 18 kernel rows per ear. The potential row number is strongly related to a hybrid’s genetics and is impacted by factors such as dry conditions, nutrient deficiencies, and improper herbicide applications.

Additionally, the tassel is initiated at or near the V6 stage, although it will not be visible without magnification. The tassel can be identifiable with plant dissection by the V7 stage.

Vegetative Stage 12 (V12)

Two photos side by side, with the left photo showing a cornstalk’s root system, stalk, and 12 visible leaves, and the right photo showing the same plant with its leaves separated from the stalk.

Plants with the 12th collared leaf are defined as V12 (Figure 7). Approximately 10% of a plant’s total dry matter is now accumulated. The lower three to four leaves will not be present due to stalk expansion and leaf losses. As with earlier stages, without the oval-shaped leaf (leaf one) as a starting point in the leaf collar method, an additional step is needed to identify the remaining collared leaves (e.g., split stalk technique or painting known leaves). The growing point continues to move upward as lower internodes become fully elongated. The tassel is already visible with careful plant dissection.

Vegetative Stage 18 (V18)

Photo depicting plant with root system growing underground and long, pointed-end leaves growing nearly upright from the top of the stalk, and the leaves underneath the top growing at 45-degree angles from the stalk.

Plants with the 18th collared leaf are defined as V18 (Figure 8). Approximately 35% of a plant’s total dry matter is now accumulated. The lower four to five leaves are not visible anymore (senesced). The upper leaves remain more vertical, at an approximately 30-degree angle, compared to the lower leaves at approximately 45-degree angles. Nearly all internodes are fully elongated except those on the stalk’s uppermost portion. The tassel continues to grow and is nearly full size.

The upper two ear shoots are similar in size. With the removal of the husk leaves, the progression of silk elongation is visible on the uppermost primary ear. The two uppermost ears are similar in size at this stage.

Tassel Stage (VT)

Two photos side by side, with photo on left showing five stages of a corn tassel’s growth from smallest (left) to largest (right), and photo on right showing the largest tassel.

Plants with all visible tassel branches extended outside the upper leaves are defined as VT (Figure 9). A plant is defined as VT regardless of whether it has begun shedding pollen (anthesis)—VT is based on when the tassel is completely visible.

Plants at VT have Vn leaves (n= final leaf) and are at maximum or near-maximum height. Most hybrids grown in the Corn Belt will have 19 to 20 leaves. The tassel is at maximum size. Although the tassel is an easy structure to identify for staging purposes, the occurrence of pollen shed is more important to document. The shedding of pollen is a determining factor in whether silks become pollinated and potential kernels are fertilized.

One specific item to note is that all tassel branches may not be fully extended above the upper leaves before the anthers on the main branch start shedding pollen. Also, silks can often be visible before the tassel is fully extended above the upper leaves; if this occurs, the plant should be defined as R1 despite VT not technically occurring first.

The length of the pollination window differs based on whether it is for the whole field or an individual plant. Plants within a field do not all simultaneously begin or end pollen shed due to plant-to-plant or field variability. Most fields will have pollen shed occurring for seven or more days. However, most pollen production lasts approximately four days. An individual plant at peak pollen production can release half a million or more pollen grains daily, although variation exists among hybrids and plant densities (seeding rates).

Reproductive Stage R1 (Silking)

Three photos side by side, with photo on left showing an ear of corn in its husk with tassel branches extended above the husk next to a partially developed ear of corn removed from the husk; the photo in the middle showing a view of a cornstalk’s roots and leaves; and the photo on the right showing the same cornstalk with it leaves separated from the stalk.

Plants with one or more silks extending outside the husk leaves are defined as the R1 stage (Figure 10). These plants have reached maximum or near maximum height and have near maximum vegetative dry matter. Determining the reproductive stage of the crop at and after R1 is based solely on the development of the primary ear (and its kernels). Silking (R1) is the only reproductive stage not defined on individual kernels’ characteristics but rather on the presence of silks outside the husk leaves.

During R1, both pollination and fertilization occur. Pollination is the transfer of pollen grains (the male portion) to the silks individually attached to an ovary (female portion). Fertilization is the joining of these two portions to create an embryo and, subsequently, a kernel. Each silk is attached to one potential kernel. A pollen grain can land anywhere on an exposed silk, leading to fertilization.

Silks remain receptive to pollen for at least five days. The first silks to appear outside the husk leaves are those attached to potential kernels near the base of the ear. Silks attached to potential kernels at the ear tip are the last to emerge and may not be pollinated if the pollen shed has ended. Some potential kernels will not develop into harvestable kernels due to a failure in pollination or fertilization. These kernels can be visible on the ear as small, undeveloped white mounds.

Reproductive Stage R2 (Blister)

Two photos side by side, with the photo on the left showing a cross section of a developing ear of corn, and the photo on the right showing an ear of corn in its husk with brown tassel branches extended above the husk next to an ear of corn with developing kernels, removed from the husk.

The R2 (blister) stage occurs approximately 10–14 days after R1. Plants defined as R2 have kernels similar to ”blisters” (Figure 11). Kernel growth begins following fertilization and consists of a rapid increase in water content with about 85% kernel moisture at the beginning of the R2 stage. Grain dry matter accumulation is minimal at this point. However, kernel size is rapidly increasing. Plants at R2 have reached maximum height and maximum vegetative dry matter. The ear is now at its final (maximum) length.

The glumes surrounding each kernel are visually less prominent as the kernels expand beyond them. Kernel expansion is occurring with the kernels now rounded, although space still exists between the kernel rows. The outside of the kernel is ivory colored, and the inside remains a clear liquid. The embryo is growing but is not distinguishable without magnification.

Kernel abortion occurs primarily during R2 and R3 and is related to an inadequate carbohydrate supply from the plant. The kernels fertilized last are those aborted first, resulting in the tip kernels most often being aborted. Silks outside the husk leaves are drying and changing from tan to light brown to brown. Silks will naturally detach from their respective kernels following fertilization, which can be seen if the husk leaves are removed and the ear is shaken.

Reproductive Stage R3 (Milk)

Two photos aligned vertically. Top photo is three different views of three corn kernels. Bottom photo is a side view of ear of corn in its husk next to an ear with kernels still developing at its tip, removed from the husk.

The R3 (milk) stage occurs approximately 18–22 days after R1. Plants defined as R3 have kernels with a “milky” interior and explode quickly when pressure is applied (Figure 12). Kernel moisture is approximately 80% at the beginning of R3. The outside of the kernel is yellow, and the inside is white and somewhat translucent. The glumes, which previously encased the kernels, and the silk scar are barely visible. Kernels fill the space between kernel rows at this stage. Starch accumulation is increasing, resulting in greater kernel dry matter. The embryo and endosperm are now distinguishable. Similar to R2, kernel abortion can still occur if the carbohydrate supply from the plant is inadequate.

Reproductive Stage R4 (Dough)

Two photos aligned vertically. Top photo is four different views of four corn kernels. Bottom photo is a side view of ear of corn in its husk next to an ear with kernels almost developed at its tip, removed from the husk.

The R4 (dough) stage occurs approximately 24–28 days after R1. The plant is defined as R4 when the consistency of the kernel interior is similar to “dough” (Figure 13). The outside of the kernel is deep yellow, and the inside is white and less translucent than at R3. Kernels have a matte finish (compared to their previous glossy appearance), and the tops are flattening. Kernel moisture is approximately 70% at the beginning of R4. Near the end of R4, kernels (often those near the base) begin to indent at their top due to increasing starch deposition and moisture loss. The cob color is hybrid-specific and can remain white or change to pink or red. The ears have husk leaves beginning to turn brown on the edges. Starch accumulation continues to increase, resulting in greater kernel dry matter. Stress during this stage will not result in aborted kernels but instead a reduction in kernel weight. An environment that is not stressful for plant development will increase carbohydrate (starch) accumulation and heavier kernels for better yields.

Reproductive Stage R5 (Dent)

Two photos aligned vertically. Top photo is four different views of four corn kernels. Bottom photo is a side view of ear of corn in its husk next to an ear with kernels almost developed at its tip, removed from the husk.

The R5 (dent) stage occurs approximately 35–42 days after R1. Plants defined as R5 have kernels that are “dented” at the kernel top due to declining moisture content and increasing starch deposition (Figure 14). Kernel moisture is approximately 60% at the beginning of R5. Ears at R5 have husk leaves fading to a pale green and browning on the edges.

At the R5 stage, a “milk line” becomes visible. The milk line separates the softer, doughy white portion nearest the cob and the starchy, solid portion at the top of each kernel. Staging kernels within R5 is possible by identifying the milk line on the non-embryo side of the kernel or by slicing the kernel lengthwise and examining it internally. Often, kernels within R5 are specifically designated by the progression of the milk line: ¼ (R5.25), ½ (R5.5), or ¾ (R5.75). Observing the milk line functions as a good, field-based tool to estimate kernel development. Progression of the milk line and the time required between each quarter varies due to temperature, available moisture, and the hybrid’s relative maturity. The time needed to reach R6 from the ¾ milk line is significantly greater than the time required for the milk line to progress between the other quarter milk line positions.

Kernel dry matter accumulation is approximately 45% of the total dry weight at the beginning of R5, leaving more than half of the dry matter to be accumulated during this stage. Once kernels have reached R5.5 (½ milk line), approximately 90% of total dry matter is already present. Environmental stress occurring during R5 reduces carbohydrates provided by the plant, resulting in reduced kernel weight and lower yields.

Reproductive Stage R6 (Physiological Maturity, PM)

Three photos, with one aligned vertically on top of two aligned horizontally. Top photo is four different views of four corn kernels. Bottom left photo is a side view of ear of corn in its husk next to an ear with developed kernels, removed from the husk. Bottom right photo is of a fully matured cornstalk with brown, dry leaves.

The R6 (physiological maturity) stage occurs approximately 55–65 days after R1. Plants defined as R6 have kernels that have reached physiological maturity (PM). Kernels at R6 no longer have a milk line because it has progressed entirely down to the tip of kernels near the cob and have maximum dry matter (Figure 15). Kernel moisture at PM is approximately 35%, with a range of at least plus or minus 2% mostly due to hybrid genetics and the environment. Leaves and stalk tissue are green and/or brown at R6, with green tissue decreasing as the plant’s moisture content decreases.

Following PM, an abscission layer (comprising accumulated carbon) forms at the kernel base, eliminating further dry matter accumulation, referred to as the ”black layer.” Physiological maturity and black layer (BL) are often used terms, although they differ. It is not possible to visually identify the exact point when a hybrid has reached PM, which is one primary reason BL is often used and recommended in determining hybrid maturity. Formation of the BL is not instantaneous and can be visually tracked as it progresses from light gray to dark brown to black. The grain moisture associated with BL is more difficult to predict than PM. Generally, it is 28% with a range of plus or minus 4%. Environmental factors and stresses, such as temperature, drought, or disease, can cause premature formation of the black layer.

Final kernel weight varies primarily due to the environment and the hybrid. Average kernel weights are approximately 350 milligrams per kernel (at 15.5% moisture) but can range from 200 to 430 mg per kernel. Therefore, assuming 56 pounds of grain are equal to a bushel, this equates to 73,000 kernels per bushel (average). An ear typically has 450 to 550 kernels based on recommended practices and a favorable environment.

Grain moisture decreases after R6 at a near linear rate, with reductions of approximately 0.5% to 0.75% per day until near 20% moisture. For predictions of corn drydown in the field developed for the northern Corn Belt, access this tool: Corn Drydown Calculator.

Environmental stress after R6 will not reduce grain yield because kernel weight is constant. Following physiological maturity, grain yield can decrease when plants or ears are damaged, examples are stalks lodging from high winds leading to ears not being picked up by combine heads at harvest or insects and wildlife feeding on ears.


View of a corn stalk that is split longitudinally at the base of the stalk and the root with text identifying the seed, and stalk nodes one through five.

Regarding crop management, we should focus on crop development as a more precise reference instead of crop growth. Younger leaves are often senesced at later vegetative stages (>V10), and other approaches are needed to stage plants accurately at the later vegetative stages. Two options are the split-stalk technique (Figure 16) or painting known leaves (e.g., leaves five and 10 on the plant). At the reproductive phase, staging is done based on kernel development.

From planting to physiological maturity or black layer, plant structures initiate and grow at different stages (Figure 1 and Table 1). In the case of modern hybrids, silks are expected to emerge (R1) before tassels are fully open (VT), as this can improve pollination. Adverse conditions like drought, heat, nutrient deficiencies, and off-label chemical applications during the crop cycle can negatively impact plants, their components, and yield.

The amount of grain harvested is the product of the classic interaction among the genetic potential of a hybrid (G), management practices for a given field (M), and the environmental conditions throughout the growing season (E). These three factors influence final grain yield by affecting yield components to varying degrees: plant/ear number per unit of area, kernel number per ear (kernel rows per ear and kernels per row), and kernel weight. These components are determined sequentially and progress during the growing season in the order they are listed (Figure 1 and Table 1).

An adequate understanding of corn’s stages of development is essential when planning activities such as applying fertilizer, herbicide, insecticide, and fungicide during the growing season. For instance, an inadequate supply of nutrients can be a critical yield-limiting factor for corn, especially during rapid uptake stages (from approximately V6 to VT). Additionally, maintaining good identification of corn staging can help in understanding when critical events occur. For example, drought stress when the crop needs highest amount of water (from about V18 to R2) can reduce kernel number and reduce yields.


Abendroth, L. J., Elmore, R. W., Boyer, M. J., & Marlay, S. K. (2011). Corn growth and development (PMR 1009). Iowa State University Extension.

Martinez-Feria, R. A., Licht, M. A., Ordóñez, R. A., Hatfield, J. L., Coulter, J. A., & Archontoulis, S. V. (2019). Evaluating maize and soybean grain dry-down in the field with predictive algorithms and genotype-by-environment analysis. Scientific Reports, 9, Article 7167.

Ortez, O., & Lindsey, A. (2023). Corn growing degree days: a method of maturity rating for hybrids [Fact sheet]. Ohioline.

Ortez, O. & Lindsey, A. (2022). Corn growth and development: crop staging. Agronomic Crops Network, Ohio State University Extension.

Ortez, O., McMechan, A. J., Hoegemeyer, T., Ciampitti, I. A., Nielsen, R. L., Thomison, P. R., Abendroth, L. J., & Elmore, R. W. (2022). Conditions potentially affecting corn ear formation, yield, and abnormal ears: a review. Crop, Forage & Turfgrass Management Journal, 8(2), e20173.

Originally posted Feb 26, 2024.