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Sorghum Growth and Development
Thierry Besancon, Ron Heiniger, Wesley Everman, and Randy Weisz
Department of Crop Science
North Carolina State University
Knowing how the sorghum plant develops is important to understand how to manage the crop.
Recognizing Key Plant Structures
Understanding crop growth and development
begins with knowing its structures and anatomy.
Key plant structures are shown in Figure 1. The first
leaf visible at emergence is the coleoptile leaf. It
differs from all of the other leaves in that it has a
rounded leaf tip. The leaf collar marks the junction
of the leaf blade and sheath and appears when the
leaf is fully developed. Each leaf sheath originates
at its own node on the plant stalk. The sheath
surrounds and strengthens the stalk (culm). The
flag leaf is the last to emerge on the plant and is
considerably smaller than the other leaves. The
panicle (head) emerges from the flag leaf sheath
and is supported by the portion of the stalk called the
peduncle.
Adapted from:
http://sanangelo.tamu.edu/programs/agr
onomy/publications/grain_sorghum/sorg
hum_plant_develop.php
Figure 1. Typical grain sorghum plants at physiological maturity
(left) and a 3-leaf growth stage (right).
Growth Stages
Stages shown and discussed range from emergence until physiological maturity. Time required to reach each
stage depends both on the hybrid and the environment in which it is growing. The times presented are for
comparative purposes only. They would change for the same hybrid at the same location if the planting date
was changed or if results from two seasons were compared. Other factors such as soil fertility, insect or
disease damage, moisture stress, plant population, and weed competition may also affect both timing of the
various stages of development and condition of the plants at each stage of development.
Adapted from:
http://weedsoft.unl.edu/documents/Growth
StagesModule/Sorghum/Sorg.htm
Figure 2. Sorghum growth stages from emergence to maturity
Stage 0. Emergence
Emergence occurs when the coleoptile is visible at the soil surface, and generally occurs 3 to 10 days after planting.
During emergence, growth is dependent upon soil temperature and moisture, planting depth, and seed ability to
germinate. Disease organisms are promoted by cool, wet conditions and such infestations would result in reduced
stands. Therefore, planting should be timed so that germination and early plant growth occur during warm
temperatures, and the reproductive phase will occur prior to the hottest part of the growing season. Now is also the
time to consider future weed control options.
Stage 1. Three–Leaf Stage
The three–leaf stage occurs when the collars of three leaves can be seen without dissecting the plant. Depending
on the temperature, this stage may occur approximately 10 days after emergence. It is important that the planting
date be late enough to ensure that warm weather will promote rapid growth at this stage. Slow growth and poor
weed control during this stage can seriously reduce yields. Although sorghum does not recover as vigorously as
corn, sorghum plants can tolerate leaf damage at this growth stage because the growing point is below the soil
surface.
Stage 2. Five–Leaf Stage
The five–leaf stage occurs when the collars of five leaves can be seen without dissecting the plant and occurs about
three weeks after emergence. The root system develops rapidly at this stage. Dry matter accumulates at nearly a
constant rate assuming growing conditions are satisfactory. The development potential of plants is determined at
this stage. Stresses from weed competition, nutrients deficiencies, drought, or insect damage can dramatically
reduce yields if not corrected.
Stage 3. Growing Point Differentiation
At this stage the growing point of the sorghum plant changes from vegetative to reproductive. At the start of this
growth stage, the total number of leaves has been determined and the potential head size is fixed shortly thereafter.
Nutrient uptake is rapid and adequate supplies of nutrients and water are necessary to achieve maximum growth.
Sorghum plants are quite competitive helping maintain good weed control over the remainder of the season. This
stage occurs approximately 30 days after emergence and is about one-third of the time from planting to
physiological maturity.
Stage 4. Final Leaf Visible in the Whorl
At this point all except the final three to four leaves are fully expanded representing approximately 80% of the total
leaf area potential. The lower two to five leaves of the plant have been lost and any reference to leaf number from
this stage on should be from the top down, counting the flag leaf as leaf number one.
Stage 5. Boot Stage
At this stage all the leaves are fully expanded, providing maximum leaf area and light interception. The head has
reached full size and is encompassed by the flag-leaf sheath. Rapid growth and nutrient uptake continue. Stress
from lack of moisture or via herbicide injury may prevent the head from emerging completely from the flag-leaf
sheath preventing complete pollination at flowering.
Stage 6. Half Bloom
This stage is defined as when half of the plants in a field have started to bloom. Flowering progresses from the tip of
the head downward over a period of 4 to 9 days. At half-bloom nearly half of the total dry weight of the plant has
been attained. This stage usually represents two-thirds of the time between planting and physiological maturity.
Severe moisture stress can result in poor head filling. However, if environmental conditions are favourable, the
sorghum plant can compensate for limitations in plant size, leaf area, or plant numbers by increasing both seed
number per head as well as seed weight.
Stage 7. Soft Dough
At this stage the grain has a dough-like consistency and grain fill is occurring rapidly. Approximately half of the seed
dry weight is accumulated between Stage 6 and Stage 7. The lower leaves continue to senesce with 8 to 12 leaves
remaining at this stage.
Stage 8. Hard Dough
By this stage approximately three-fourths of the grain dry weight has been attained. Nutrient uptake at this point is
essentially complete. Severe moisture stress caused by an early freeze at this growth stage can result in light,
chaffy grain.
Stage 9. Physiological Maturity
At this stage the maximum total dry weight of the plant has been reached. This stage is marked by the appearance
of a dark spot on the opposite side of the kernel from the embryo. Grain moisture at physiological maturity depends
on the hybrid, with typical moisture ranging from 25% to 35%. Hybrid and weather conditions affect the time
between maturity and the proper harvest time.
References
Gerik, T., B. Bean, and R. Vanderlip, Sorghum Growth and Development, Texas Cooperative Extension Service. 2003.
Nordby D., Pocket Guide to Crop Development: Illustrated Growth Timelines for Corn, Sorghum, Soybean, and Wheat,
University of Illinois Extension Service. 2004.
Vanderlip, R. L., How a Grain Sorghum Plant Develops, Kansas State University, 1993.
Warrick B. E., How a Sorghum Plant Develops, Texas AgriLife Research & Extension Center, 2000.