This interactive diagram demonstrates the different growing stages of alfalfa. These elements are important for understanding nutrient and fertilizer management. Click on the MORE buttons below for further information on each factor. Germination and Emergence The seeds will begin to absorb water about hours after planting, if enough moisture is available. Temperatures between and degrees Fahrenheit and degrees Celsius 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. Fields may be difficult to enter into due to wet soils, but alfalfa may be planted as soon as danger of spring frost has passed.
Summer weed competition can be alleviated by planting with an annual companion crop such as oats. Alfalfa, during growth, is not tolerant of a high water table that could drown it out. Equally as important is that the site receive enough water for successful growth.
Sandy to clay loamy soils are best. Sand dominated or clay dominated soils will pose problems to water management. Planting in the first two weeks of August is a possibility IF soil moisture is sufficient. Alfalfa requires a minimum of six weeks after germination, and before a killing frost to ensure survival. At least four trifoliate leaves and the formation of a crown are necessary for winter survival.
Advantages of a late summer planting are a decreased competition with weedy species and an increased yield the following year when compared with spring planting. However, late summer plantings come with higher risk due to unpredictable rainfall and early frost. Stage of Alfalfa for Winter Survival M. Bohle, personal communication, August 14, Undersander, Dan et. Alfalfa Management Guide. American Society of Agronomy, Inc.
Dwain Meyer. Benton et. Intermountain Alfalfa Management.
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