Alfalfa Development and Growth Staging
Considered the Queen of the forages, alfalfa is one of the most popular and important forage crops grown in North America.¹ In the United States, it’s the fourth most valuable field crop bringing in $8.8 billion annually.² It’s well adapted to North American soils (with the exception of the southeastern United States) and has become a valuable forage crop for hay, haylage, green chop, pastures, and animal feed for a variety of livestock including dairy cows, beef cattle, horses, sheep, chickens, and other livestock. Alfalfa sprouts are also produced for human consumption.
Alfalfa is highly nutritious and produces more protein per acre than any other crop.² It’s rich in both vitamins (A, D, E, K, U, C, B vitamins, etc.), and minerals (phosphorus, calcium, potassium, sodium, etc.).²
Managing Alfalfa for Maximum Yield and Quality
Producing high-yielding, quality alfalfa requires a strong understanding of its growth throughout production. A deep understanding of each stage of development will help you better manage the crop from planting to harvest. Certain fertility decisions are only effective at specific stages of development, and factors like the climate and soil conditions can impact the evolution of growth. Thus, it is important to better understand alfalfa’s growth stages and development cycle to make more informed management decisions while meeting your productivity and profitability goals. Knowing what stage of growth your crops are in will also allow you to better manage their health, assess crop quality, and determine the best time to harvest.
The Four Phases of Alfalfa Growth
The growth stages of alfalfa crops can be broken into four parts: vegetative, flower bud development, flowering, and seed production. After planting, alfalfa seeds begin germination. Germination relies on adequate soil conditions. Alfalfa seeds will not germinate in soil temperatures below 35°F (1.7°C) or above 104°F (40°C). Adequate soil moisture is also critical. Then, alfalfa crops enter nine stages of development including the early vegetative, mid-vegetative, late vegetative, early bud, late bud, early flower, late flower, early seedpod, late seedpod, and ripe seedpod stages. Click through each of the MORE buttons below to learn more about each stage of development.
VEGETATIVE
Germination and Emergence
The seeds will begin to absorb water about 24-48 hours after planting if enough moisture is available. Temperatures between 65°F and 72°F (18°C and 22°C) are optimal for alfalfa germination. As water uptake begins, a radical root emerges forming a taproot anchoring the seed to the ground. The hypocotyl, the initial seedling stem, forms and straightens, pulling the seed coat up through the soil. Seeds should not be planted deeper than half an inch and at the recommended seeding rate. A soil test should be done, and nutrients should be applied according to soil-test results. Soil preparation before planting is the best time to apply important immobile nutrients like phosphorus and potassium.
Seedling Growth and Establishment
Cotyledons are the first visible structures above the ground. A unifoliate leaf is the first true leaf produced. If the alfalfa seed is not fungicide treated, apply fungicide to prevent seedling diseases. Control weeds within the first 60 days to prevent stand loss.
First Trifoliate Lead and Buds
During this stage, the first trifoliate is formed. This is a second leaf and has three leaflets. As the plant is maturing it produces alternately arranged trifoliate leaves. During this stage, photosynthesis is sufficient to meet all energy requirements by the alfalfa seedling. The first few buds develop in the axils of all leaves, where secondary stems can originate.
Contractile Growth and Crown Development
This stage begins one to two weeks after emergence and is completed at 16 weeks. Contractile growth is a process in which the hypocotyl shortens and grows thicker. This is a result of carbohydrate storage within the plant. This stage pulls the cotyledonary node and the unifoliate node beneath the soil to form the crown. Critical crown buds form during this time. Alfalfa should be planted in time to allow the crown and crown buds to fully develop before winter.
Root Development Nitrogen Fixation
During this stage, the alfalfa will cold harden. The plant needs shorter days and a minimum of two weeks of near-freezing temperatures to become dormant. The plant will convert starch in the crown to anti-freezing sugars to help keep the plant alive through winter. Before the winter dormant stage, the last cutting should leave eight to 12 inches of stubble, or four to six weeks of growth time. This will allow adequate time for root reserve replenishment. Adequate potassium improves winter survival by improving carbohydrate storage in the roots.
Spring Green-Up
This stage begins when the crown buds start to grow in response to warmer temperatures during the spring. Spring growth comes from crown buds formed during the previous summer and fall. Spring green-up is affected by plant health, dormancy requirements, and fall weather conditions. Uneven growth indicates winter injury. Injured plants are less vigorous and lower yielding. A soil test will help determine the nutrients needed.
CUTTING MANAGEMENT
When to Cut
When deciding to cut, consider forage yield, quality, and stand presence. The forage yield will increase until the plant reaches full flower, but the quality will decrease with maturity. The optimum time to maximize both yield and quality is around the late bud stage to early bloom, depending on the nutrient requirement and livestock species. Scout for alfalfa weevils and potato leafhoppers, as both feed on the buds.
Growth after Cutting
Ideally, cutting should occur two inches above the soil surface to preserve axillary buds and next cutting yield. Cutting shorter than two inches will impact regrowth. Regrowth will commence more rapidly if alfalfa is harvested before axillary buds reach cutting height and new growth is not disturbed by cutting.
Sources:
¹University of California, Alfalfa In North America
²North American Alfalfa Improvement Conference, Importance of Alfalfa
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