This full-color booklet presents, in word and picture, the story of how an alfalfa plant develops from the moment the seed swells and the radicle bursts forth to anchor in the soil, till the plant flowers-and it simultaneously describes how to make alfalfa thrive by careful management techniques.
Understanding the details of how alfalfa plants grow will help farmers grow better alfalfa. Knowing how the alfalfa germinates will help them create conditions necessary for good stand establishment. Knowing how seedlings develop will be useful in determining when to control diseases, insects, and weeds. Understanding patterns of growth-spring green-up and growth after cutting-will aid in identifying winter injury and disease problems, and in managing weeds. And being familiar with the mature stages of alfalfa growth will be helpful when making decisions about when to cut to ensure the maximum yield of the forage quality required.
Considerably revised from earlier editions, Alfalfa Germination and Growth presents a thorough description of how alfalfa is best managed (18 pages; 2011).
Alfalfa, also known as lucerne, is an important perennial forage crop grown around the world With its high protein content and ability to fix nitrogen, alfalfa is a versatile crop used for hay production, grazing, and soil improvement. However, successfully growing alfalfa requires an in-depth understanding of the different stages of growth the plant goes through. In this article, we will take a deep dive into the growth cycle of the alfalfa plant and the key characteristics of each stage
Germination Sets the Stage
The growth journey of an alfalfa plant begins with the germination of the seed. This involves the seed absorbing moisture from the surrounding soil and initiating the growth of the embryonic root and shoot. Under optimal temperature conditions of 65-70°F alfalfa seeds usually germinate within 7-10 days. As the radical and hypocotyl emerge, the seed coat is shed and the cotyledons or seed leaves are exposed to sunlight to start photosynthesis.
During germination, it is critical to ensure adequate soil moisture and proper planting depth for the tender roots and shoots to establish themselves. Planting too deep can impede emergence while drying out of the topsoil can desiccate the seedlings. Timely germination leads to uniform establishment of a robust alfalfa stand.
The Seedling Phase: Building a Strong Foundation
Once germinated, the alfalfa seedling enters a period of rapid development lasting 3-4 weeks. This stage is marked by the growth of the highly branched taproot system that delves deep into the soil profiling for moisture and nutrients. The seedling also puts out several leaves while its stem elongates rapidly.
The seedling stage is all about establishing a vigorous root system and leaf canopy to harness sunlight and soil nutrients. Make sure the tender seedlings are protected from intense sunlight, wind damage, frost or insect pests. Moderate moisture and cool temperatures are preferred at this stage. Early weed control is also critical to reduce competition. Overall a strong start in the seedling phase forms the foundation for higher yields down the road.
Vegetative Growth Takes Center Stage
As the alfalfa plant matures, it enters an extended vegetative phase focused on accumulating leaf and stem growth. This stage can last several months based on variety, environment, and management inputs. The crown of the alfalfa plant starts to thicken as more trifoliate leaves are produced from the alternate buds. Axillary shoot growth and tillering also pick up pace during this phase.
Maximizing vegetative growth is key to building up the food manufacturing capacity of alfalfa. As foliage accumulates, the plant intercepts more sunlight to synthesize carbohydrates through photosynthesis. These carbohydrates fuel the expansion of the root system as it probes deeper subsoil layers. Vegetative growth is also vital for plant recovery after cuttings and needs to be balanced against reproductive development.
Flowering Signals a Change
The transition from vegetative to reproductive growth starts with the initiation of flowering buds at the shoot apices. Visible bud formation occurs around the time the plant reaches 10% bloom stage. Soon the buds blossom into flowers that attract pollinators like bees, leading to seed pod development.
Flowering marks a major shift in plant priorities as energy is now diverted to reproduction. Nutrient levels also decline in the herbage as morenon-structural carbohydrates are translocated to the seeds. Hence, the time of first harvest is critical to optimize forage yield and quality before excessive flowering diminishes feed value.
Seeds Mature as the Life Cycle Culminates
Pollinated alfalfa flowers give rise to spiralled seed pods that turn from green to brown as seeds mature. Inside each pod, 5-20 seeds develop that are reliant on adequate moisture and nutrition. Mature seeds have a hard seed coat and high germination capacity for sowing future crops.
Harvesting alfalfa for seed production requires precise timing when the pods turn brown and seeds reach physiological maturity. Any delays can lead to shattering seed losses. The seeds are then dried, cleaned and scarified for sale as certified seed for planting next season.
Dormancy Aids Survival
After completing its life cycle, the alfalfa plant enters a period of winter dormancy as light and temperature cues suppress growth. This survival mechanism allows the plant to conserve energy reserves in the taproot through the harsh weather until spring.
During dormancy, the plants stop active growth and lose their leaves. Weed control and maintaining soil fertility are key preparatory tasks before the dormant season. Come spring, the alfalfa crowns will use their stored carbohydrates to resume vegetative growth.
The Growth Clock Keeps Ticking
The alfalfa plant is a perennial that can go through multiple cycles of growth and dormancy over its lifetime of 3-12 years. With every spring green-up, the clock resets as the plant transitions again from dormant to vegetative phases. Leaf area is restored through shoot growth from both crown and axillary buds.
Managing alfalfa through these recurring phenological stages requires a keen eye and timely agronomic interventions. Whether it is harvest scheduling, pest control or fertilization, the needs of the crop change with its physiological age. Keeping pace with the alfalfa’s growth rhythms is central to realizing the genetic potential of each plant.
Tracking Growth Progression
To align crop management with the alfalfa’s developmental needs, producers need to regularly monitor and measure its stages of maturity. Here is a simplified guide to the visual indicators that define the progression of an alfalfa plant through its life cycle:
Vegetative Stages
- Stage 0- Early Vegetative: Stem length <6 inches, no buds visible
- Stage 1- Mid Vegetative: Stem length 6-12 inches, axillary leaf growth visible
- Stage 2- Late Vegetative: Stem length >12 inches, buds palpable but not visible
Bud Development
- Stage 3- Early Bud: 1-2 nodes with visible buds
- Stage 4- Late Bud: More than 3 nodes with visible buds
Flowering
- Stage 5- Early Flower: One node with open flower
- Stage 6- Late Flower: More than two nodes with open flowers
Seed Production
- Stage 7- Early Seedpod: 1-3 nodes with green seedpods
- Stage 8- Late Seedpod: More than 4 nodes with green seedpods
- Stage 9- Ripe Seedpod: Nodes with brown, mature seedpods
Optimizing Growth Requires Diligence
While we have skimmed through the major phases in the development of the alfalfa plant, the devil lies in the details. Growth is affected by complex interactions between the genetics of the variety chosen, local soil and climatic factors, and management inputs.
To optimize each stage, producers need to regularly walk and inspect their alfalfa fields. Soil testing, tissue sampling, pest scouting, and canopy photography should accompany visual monitoring. Matching crop demands to soil nutrients, moisture and light resources is paramount.
Record keeping is equally vital to evaluate the outcomes of management tactics over time. Growth tracking and field history data guides fine-tuning decisions for improved yields and crop health. Adopting such diligent agronomic practices is key to harnessing the full genetic potential of alfalfa across its life cycle.
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Alfalfa Growth Stages for on-farm Decisions
FAQ
What are the growth stages of alfalfa?
How long does alfalfa take to grow?
At what temperature does alfalfa stop growing?
What does alfalfa look like when it blooms?
How do alfalfa plants grow?
As the seedling emerges from the soil, it develops cotyledons that provide energy for early growth until true leaves appear. Once the seed has germinated, the alfalfa plant enters the seedling stage. This stage is characterized by rapid growth as the plant establishes its root system and develops its first true leaves.
What stage does alfalfa grow?
Vegetative Stage: During this stage, alfalfa produces leaves and stems but no flowers. It’s a critical period for building biomass. Bud Stage: Alfalfa begins to form buds, signaling the transition from vegetative to reproductive growth. Early Bloom Stage: The plant starts to produce purple or blue flowers.
When does alfalfa grow hay?
It’s a critical period for building biomass. Bud Stage: Alfalfa begins to form buds, signaling the transition from vegetative to reproductive growth. Early Bloom Stage: The plant starts to produce purple or blue flowers. This stage is ideal for hay production due to high forage quality.