Wheat Growth Stages: In-Depth Crop Management Guide

The BBCH-scale is a crucial tool for evaluating wheat's growth regarding agricultural standards and making informed management decisions. Particular varieties may have somewhat different durations and specifics for each stage of wheat growth, but these distinctions do not affect the fundamental features. You need to keep an eye out for weeds, pests, and diseases while growing crops, water them enough throughout crucial plant growth stages, and apply fertilizer, especially nitrogen, at just the right times. If you follow the expert advice, you'll be able to pick the best time to do the necessary field activities and get the most out of your inputs throughout all wheat growth stages.

BBCH For Wheat Growth Stages

A leaf is only counted as present in BBCH-scale when it is fully unfurled. Tillering, as well as stem elongation, may happen before growth stage 13, in which case you should move on to stage 21. Also, keep going with growth stage 30 if stem elongation starts before tillering is done.

Wheat plant growth stages according to BBCH-scale

BBCH 00–09: Germination

Wheat growth, development, and yield are all affected by whether or not the required conditions are met for this wheat variety. Talking about winter wheat, one peculiarity is that despite vigorous seedlings growth, it does not produce stems and ears when sown in the spring. Winter wheat requires a period of vernalization at a temperature from -17 to -16 to -19°F (0 to 3°C) for 35 to 60 days to ensure full-fledged plant growth and development.

Seeds need a warm, moist environment throughout the wheat germination stage. Seedlings will emerge in about a week under ideal growth conditions. Up until the first leaf is functional, the seedling can survive on the seed-stored energy and nutrients.

For sowing, opt for certified wheat seeds, or carefully clean and size the seeds you have. Seeds treated with fungicides and insecticides can better withstand diseases and pests during the early wheat growth stages. Starter fertilizing winter wheat in the fall with 30 to 40 pounds of nitrogen per acre (34 to 45 kg/ha) is also advised to promote wheat growth throughout all stages.

Appropriate Crops For Rotation

Wheat imposes strict requirements for crop rotation. Well-fertilized rapeseed is the ideal antecedent for winter wheat growth, but legumes, sugar beets, late potato varieties, melons, and buckwheat will also work. Winter wheat should wait at least two to three years before being planted in the same field again.

To prevent the spread of common pests and diseases, spring wheat should not be sown after any other cereals except oats. In addition, plants do not thrive in monoculture or when the previous crop, such as sorghum, sunflower, or alfalfa, tends to dry out the soil.

Deciding On Row Spacing And Sowing Dates

Stand establishment is the most important factor in maximizing wheat yields. Since there is less time for the tillering growth stage in late-planted wheat, a higher seeding rate is recommended. Under normal conditions, 2–2.4 million seeds per acre (5–6 million seeds per hectare) is the sowing rate for optimum stands. At this rate, narrow-row sowing with 3 inches (7.5 cm) between rows gives the plant roots a much better nutrition area than wide-row sowing with 6 inches (15 cm) between rows, but the narrower space between plants may not be enough for primary tillers’ growth. These factors should be considered when determining wheat row spacing.

Sowing dates vary depending on the field’s climate zone as well as temporary growth conditions. Planting of tropical wheat hybrids typically occurs between corn and soy crops in March through June ^{Vitosh, M. L. Wheat Fertility and Fertilization. Michigan State University.}; however, two or even three wheat harvests during the year are possible in tropical and subtropical regions. Instead, in the temperate zone, careful forethought is required to ensure:

• the crop receives sufficient light, heat, and moisture for its germination and growth in the case of spring sowing;
• the crop goes through all the critical growth stages of wheat required to survive winter colds in the case of autumn sowing.

To help farmers recognize weather patterns and choose optimal sowing times, EOSDA Crop Monitoring provides them with historical weather data and forecasts. If you are planning to sow wheat for the first time in a particular field, productivity maps from previous seasons will facilitate variable rate seeding.

Sufficient Soil Moisture

The moisture content of the soil has a direct effect on how quickly seeds pass through the germination stage of wheat plant growth. The process is faster in moist growth conditions and slower when soil moisture levels are near the permanent wilting point. To illustrate, at 44°F (7°C), the wheat germination stage takes 10 days when the soil is at the wilting point, rather than 5 days when there is plenty of moisture. Depending on the amount of moisture present, the seed’s germination process can pause or resume.

Inadequate soil moisture also hinders wheat growth, which in turn reduces crop yields. A lack of moisture is most damaging to winter wheat during the growth stages of stem elongation, earing, and grain filling, when the plant’s water demand is highest. The daily and accumulated precipitation features of EOSDA Crop Monitoring allow farmers to determine whether or not their crops need supplementary irrigation or drainage at all stages of wheat growth.

Optimum Soil Acidity

Wheat requires a soil pH of 6-7 for optimal growth. Poor organic nitrogen (N) mineralization, lack of magnesium (Mg), limited phosphorus (P), and higher toxicity from manganese (Mn) and aluminum (Al) are some of the problems that come up when the soil acidity is below 6. Crops may also experience a Mn deficiency throughout all wheat growth stages if the soil pH is greater than 7. For monoculture wheat cultivation, lime your fields to a pH of 6.5, whereas in a rotational cropping system, lime to the pH needed for the most demanding culture ^{Abe, N., Vieira, R. (2022, August 18). Brazil Has High Hopes for a New Strain of Wheat. Spiegel International.}.

Suitable Air And Soil Temperatures

Temperature plays a key role during the germination wheat crop growth stage. Temperatures between 54 and 77°F (12 and 25°C) are optimal for germination; 20–25°C results in the fastest germination, while 12–17°C results in the most seedlings. Still, temperatures ranging from 39 to 98°F (4 to 37°C) are also suitable at this critical stage of wheat growth.

Accumulated temperatures and degree days (the mean of the highest and lowest temperatures over successive days) hasten germination. Wheat needs 35 degree days for seed germination to become evident. For instance, at 45°F (7°C), noticeable germination takes 5 days, but just 3–5 days at 50°F (10°C).

High soil temperatures can damage establishing seedlings. During heat waves, bare soil temperature might increase to as high as 104–113°F (40–45°C), significantly affecting emergence. A decline in the wheat population during the early stages below the threshold of 9 plants per square feet (100 plants per square meter) is detrimental to yield. Mulching works as a barrier between the ground and the environment that helps reduce water loss through evaporation and cool down the soil, making it an effective means of preventing the soil from drying out, especially paired with irrigation.

To inform your wheat sowing decisions, EOCDA Crop Monitoring provides historical weather data, such as sums of active temperatures and daily minimums and maximums.

Moreover, you may keep tabs on the daily temperatures in selected wheat fields, set critical temperature thresholds for your crops, and get notified when the temperature reaches or drops below those thresholds.

BBCH 10-19: Leaf Development

The coleoptile, which emerges from the ground, stops developing once it sees light. The first true leaf is about to emerge from the coleoptile’s apex. During the wheat leaf stage, 3 leaves will evolve to their fullest. This is also the time when a crown establishes between the seed and the ground, and the seminal root system kicks off its growth.

Growers should check their fields at this wheat plant development stage to make sure the plants are evenly spaced and have a stand of around 15–25 plants per square foot (160–270 plants per square meter). Keep an eye out for weed growth, and if you notice any, don’t hesitate to spray herbicide. It’s crucial to scout for pests at the beginning of the growth season, as you’ll need to spray if you detect more than 10 wheat aphids per foot (33 per meter) of row ^{Eros, F. (2023, February 21). How a Wheat Plant Develops: Identifying Growth Stages. Alabama A&M University and Auburn Universities Extension.}.

Using MSAVI maps is especially helpful at this stage in the wheat growth cycle. Early-stage monitoring of vegetation development rates helps infer nutrient deficiencies or excesses, unfavorable soil physicochemical conditions, excessive or insufficient moisture, as well as the growth of weeds and pests in the field. Thanks to these findings, you’ll be able to act quickly and prevent serious crop damage.

BBCH 20–29: Tillering

During this wheat growth stage, tillers form on the main stalk at the coleoptile and lower leaf attachments. Secondary tillers can develop from primary tillers if the plant has enough room and is given plenty of fertilizer. The tillers have the best chance of maturing into grain if they appear between the emergence of the fourth and sixth main shoot’s leaves. Later-forming tillers have a higher risk of failing to produce grain. Abortion of tillers occurs at varying rates, depending on the wheat hybrid, and may be amplified in stressed crops.

Another crucial process starts during the tillering stage of wheat’s growth cycle: the set-up of heads on the main stalk and tillers. Even though the head is still very young and small at this point, it is already creating the elements that will develop into the flower parts and kernels.

The Effect Of Tillering On Wheat Yields

Wheat’s ability to tiller is a positive trait. Tillers contribute 30–50% of yield across most varieties and hybrids. At the same time, they may even account for as much as 60–70% of yield in liquified crops. Under normal conditions, high yields can be expected from tillering with as few as two or three lateral shoots.

Fertilizing To Promote Tillering

When planting wheat, especially within the no-till farming approach, growers often apply starter nitrogen to stimulate tillering. Further fertilizing in the early spring during the BBCH 25 wheat stage of growth will promote the tillering process and increase stem density. The crop health and the rate at which spring vegetation recovers will determine how much N to apply for this feeding. Typically, it is recommended that well-developed wheat crops receive 30% of the overall nitrogen rate for the growth season.

In the table below, you’ll see the guidelines for how to administer single and NPK fertilizers to winter wheat at different stages of its growth. The specifics of fertilizing will be discussed in greater depth within the appropriate growth stages.

General application guidelines for single and NPK fertilizers in the winter wheat

A soil pH of 6.0 or higher and an adequate supply of phosphorus encourage root and tiller growth in wheat. Productivity maps in EOSDA Crop Monitoring are an excellent tool for implementing variable rate applications (VRA) of nutrients like phosphorus and potassium. That is to say, you can apply as much fertilizer as is needed in a certain wheat field area, depending on its productivity. Remember that soil acidity affects the efficiency of both macro- and micronutrients, so you might need to make some tweaks.

Tillering Peculiarities In Winter Wheat

Winter wheat stands out because of how well it tillers. The tillering stage of winter wheat varieties may take several weeks longer than the same growth stage of spring wheat. Depending on the sowing date and climate, winter dormancy may or may not stop tillering. It’s not typically an issue, though, since most of the tillers that grant yields have developed by now.

BBCH 30-39: Stem Elongation

The jointing stage in wheat, when the plant’s growing point appears above the ground, marks the beginning of stem elongation. While the internodes in the lower stem of a wheat stay short throughout the whole plant’s growth cycle, the length of the internodes up the stem is progressively increasing.

Until the stem elongation stage of wheat growth the bulk of tillers have developed, whereas the secondary root system is expanding and the leaf sheaths are stiffening. At this point in its growth, winter wheat starts to stand up straight, even if it had a more prostrate growth pattern before. As a field becomes uniformly green due to the fresh spring plant growth, this period is known as a green-up.

Winter wheat nitrogen fertilization in the spring should wait until after the green-up stage. If fertilization was not possible at earlier stages of wheat growth due to weather, wheat can still benefit from N provided during stem elongation, but applicator equipment must be handled with the utmost caution to prevent mechanical damage to plants. Regular checks for pests and weeds are an essential part of crop maintenance at this growth stage.

BBCH 40-49: Booting

The head is fully grown during the wheat boot stage and may be seen in the swelling area below the flag leaf. Application of nitrogen to wheat at the flag leaf stage or later may increase grain protein content, but its effect on grain quantity growth is doubtful. Furthermore, N-fertilization may worsen foliar diseases, especially rusts. At this growth stage, fungicides are crucial for foliar disease control aimed at preventing the spread of rusts, as well as Stagonospora nodorum leaf and glume blotch.

The flag leaf accounts for about 75% of the effective leaf area responsible for wheat grain fill; therefore, keeping it free from pests and diseases is crucial for optimal grain development. Similar to how we used MSAVI maps to examine wheat’s early development, NDVI can be used to analyze crop health at the boot growth stage of wheat. Colors ranging from yellow to red on the NDVI map indicate potential hotspots where a scout should be dispatched for a closer look and a report back.

BBCH 50-59: Inflorescence Emergence, Heading

All of the inflorescence and flower organs are fully formed at this wheat phenological stage. The groundwork for the eventual grain number per spikelet, and thus crop production potential, is now built.

Providing nitrogen from the start of the heading to the grain filling stages can increase the duration of the upper leaves’ activity, the intensity of photosynthesis, and the mass of the grains. Delaying nitrogen fertilization reduces its impact on production but increases its impact on grain quality, particularly in the development of whole grains with high levels of protein and gluten.

At this growth stage, wheat is particularly susceptible to foliar fungal infections. Early-season disease protection and the development of plant vigor can be achieved through routine scouting and the application of fungicides. From now on, phenoxy herbicides are typically employed to control weed growth in wheat.

BBCH 60-69: Flowering, Anthesis

The middle spikelets’ florets are the first to flower within days after the heading growth stage. Fungicides are most effective against Fusarium head blight and vomitoxin when applied at the onset of the wheat flowering stage.

One sign of the flowering stage in wheat plants is the extrusion of anthers from florets, even though this identifier can vary with hybrid and climate. Many flowers get pollinated before the anthers even open. If the anthers are no longer green but instead yellow or gray, then pollination has most likely taken place.

Within one individual head, pollination takes around four days. At the pollination wheat development stage, there is a wide range in size among the immature kernels inside a head, and this variation stays the same throughout grain filling and crop maturation ^{Bongard, P. et al. (2021). Spring wheat growth and development guide. University of Minesota Extension.}. While it can take just 13 days for the grain to fill in low-yield, stressful growth conditions, the process can take well over 20 days in high-yield, favorable conditions.

BBCH 70-79: Development Of Fruit

At this stage of wheat growth, an accumulation of nutrients in the grain happens. The grains get wider and thicker, and their content turns milky.

There are two smaller stages of fruit development stage: kernel watery ripe (BBCH 71) and milky ripe (BBCH 73–77). These are named after the colors and qualities of the liquid that comes out when you crush the kernel. Grain size increases rapidly during the watery ripe stage, although there is little growth in dry matter. During the milk stage of wheat ripeness, 15–18 days after flowering, the growth of endosperm solids occurs due to photosynthates.

Farmers’ best allies during the fruit development stage are continuous monitoring of crop health and, if necessary, applying biological or chemical protection against grain pests and diseases.

BBCH 80-89: Ripening

The initial consistency of the kernels at this time is used to divide the ripening stage into three distinct sub-stages:

• Early dough (mealy ripe) stage of wheat. Extreme heat/water stress during this growth stage may diminish wheat grain test weight, so ensure enough irrigation now.
• Soft dough stage of wheat. The bulk of the kernel’s eventual mass is accumulated at this growth stage.
• Hard dough stage of wheat. During this growth stage, the moisture content of the kernel drops from 40% to 30%. Kernels reach their largest dry weight and physiological maturity.

During the ripening stage, it is crucial to monitor the wheat crop for signs of heat and water stress and take corrective action as soon as possible. All that’s needed to start getting timely automated notifications from EOSDA Crop Monitoring for tracking heat stress in plants is to set the field’s temperature threshold. And when it comes to detecting and evaluating water stress, soil moisture charts and NDMI index maps are excellent resources.

With historical precipitation data for the area of interest, you can devise an irrigation strategy in light of local weather patterns, thus making up for any deficits in rainfall and preventing water stress on your wheat crops at the ripening stage.

After successfully passing all the previous growth stages, the wheat crop becomes physiologically mature, which means the kernels stop gaining dry weight and quickly lose moisture. The crop should be picked when the moisture level is between 13 and 14% to cut down on post-harvest drying expenses and set the stage for safe storage.

BBCH 90-99: Senescence

The hardening of the grain and the complete dryness and death of the plant are hallmarks of the senescence development stage in wheat. Early senesce in wheat plants brought on by heat stress or soil salinization might reduce crop output.

When crops are harvested, the crowns and straw are left on the ground. They are part of the stubble, which might also include the chaff and straw left by the harvester. Historically, burning stubble was a common practice among grain producers as a means of reducing biomass and weed growth before sowing. It is no longer the recommended course of action, though.

Stubble mulching is a viable option for managing crop residue. This helps conserve soil moisture and facilitates the decomposition of residue. Wheat farmers may need to reevaluate their stubble handling practices from time to time, depending on crop rotations and other factors crucial to achieving optimum crop growth and maximum yields.