As an alfalfa grower, understanding the root and stem anatomy of this important forage crop is key to proper management and maximum productivity. Below, we take an in-depth look at the unique structures and functions of alfalfa roots and stems.
Alfalfa Root System
Alfalfa roots grow rapidly, extending multiple feet into the soil This expansive root system allows alfalfa to tap water and nutrients far below the surface.
Taproot
- Primary root that forms at germination and anchors the plant
- Grows vertically downwards, can extend 20 feet or more into soil
- Woody and carrot-shaped, up to 1 inch diameter
- Stores carbohydrate reserves to regrow shoots after cutting
Lateral Roots
- Branch horizontally outward from taproot
- Spread 18 inches to 5 feet deep in soil
- Absorb water and minerals, interact with soil microbes
- Fine root hairs further increase surface area for uptake
Crown Buds
- Located at top of taproot near soil surface
- Each bud can develop into a new shoot or stem
- Enable alfalfa to regrow after harvest by activating new shoots
- More buds means better regrowth potential after cutting
Rhizomes
- Horizontal underground stems growing from crown
- Allow alfalfa to spread via new shoots from rhizome tips
- Help alfalfa persist by spreading plants under soil
- Provide carbohydrate storage for overwintering
Nodules
- Small round structures formed on roots
- Contain nitrogen-fixing rhizobium bacteria
- Convert atmospheric nitrogen into plant-usable forms
- Supply alfalfa with nitrogen without fertilizer inputs
Alfalfa Stems
Alfalfa stems support leaves, flowers, and seed pods above ground. Stem characteristics influence crop yield and quality.
Axillary Buds
- Located where leaves attach to stems
- Can produce new shoots and stems after harvest
- More buds per stem means more rapid regrowth
- Cutting height impacts bud survival and plant regrowth
Nodes
- Points where leaves are attached along the stem
- Sections between nodes are called internodes
- Shorter internodes improve leafiness and nutritive value
- But too short causes reduced resilience and yield
Hollow Stems
- Alfalfa stems are hollow between individual vascular bundles
- Allows stems to stand upright under heavy foliage
- Improves drying time of hay by allowing air movement
- Can reduce leaf loss and nutritional quality if cut too dry
Extracellular Lignin
- Hardened compound strengthens and stiffens stems
- Allows alfalfa to regrow multiple times after cutting
- Lignin content increases with maturity
- Excess lignin lowers digestibility and feed quality
Growing Point
- Area of new cell growth at stem tips
- Produces new leaves and stem elongation
- Removal by harvest or grazing stimulates bud growth
- Cutting height impacts regrowth rate and vigor
Sold by the Bulk Pound
Medicago sativa L., alfalfa, is a long-lived perennial 1egume. Flowers vary in color from purple to yellow and are borne in loose clusters. Pods of alfalfa range from the sickle type to those that are twisted into spirals. Each pod contains several small kidney shaped seeds. Alfalfa’s stems are erect and grow from a woody crown to about 2 to 3 feet tall. New growth occurs from buds in the crown. The plant has a tap root which may penetrate deep into the soil. Leaves are alternately arranged on the stem and are normally trifoliate.
Crops: Alfalfa is harvested as hay which is processed or fed directly to livestock, or for seed production. It is also used in pellets as forage supplements.
Livestock: This plant is grown in combination with grasses in improved pastures. It is grazed by all types of domestic livestock. Caution should be taken when using alfalfa for grazing due to its high bloat hazard.
Wildlife: Alfalfa is an excellent food for antelope, deer, elk, Canada goose, and sage and sharp tail grouse. It is fair food for sandhill crane, mallard, Hungarian partridge, and pheasant.
In addition to providing high quality hay, grazing, and wildlife forage and protection, alfalfa is an important source of leaf meal used for fortifying baby food and other special diet foods prepared for human use. Large quantities of dehydrated alfalfa are also used in manufacturing concentrated feeds for poultry and livestock.
Alfalfa grows best on deep, well-drained, friable soils. Lands subject to frequent overflows or high water tables are unfavorable for alfalfa. The pH of the soil should be 6.5 or above. Alfalfa is distributed throughout the entire United States. For a current distribution map, please consult the Plant Profile page for this species on the PLANTS Website.
A seedbed must be smooth, firm, free of weeds and trash, and contain adequate moisture for germination and emergence. Land grading must be sufficient to ensure good surface draining. Alfalfa should not be seeded as a first crop on newly leveled land where fill may settle and cause poor surface drainage. Five pounds of scarified, properly inoculated pure live seed (PLS) per acre evenly drilled ¼-inch deep on adapted, properly prepared sites will produce adequate stands. A combination drill and packer is desirable. Cultipacking soil before and after seeding is helpful to establishing a stand. Seeding depths should be no greater than ¼ inch on finer textured soils and no greater than ½ inch on sandy soils Spring seedings can be made 30 days before the average date of last killing frost. Other dates of seeding may be made during the late summer.
In general, graze or cut for hay when alfalfa is in early bloom. Graze or cut to about a 2-inch height. Successive grazings and cuttings for hay should occur at ¼ bloom stage or after a 5 to 6 week recovery period. Alfalfa can best withstand grazing if rotated frequently or grazed in small strips. The last cutting of alfalfa should be made 3 to 4 weeks before the first killing frost date. Alfalfa may cause livestock to bloat. Care should be used in managing such grazing to reduce the possibility of this hazard.
Plant Root System & Shoot System
FAQ
How deep are the roots of alfalfa?
How deep is alfalfa planted?
What does an alfalfa plant look like?
What is the structure of alfalfa plant?