Alfalfa: growing, harvesting & benefits
Alfalfa is mainly cultivated for green manure and as feed, especially for horses. It is valued for its high protein content and impressive dry matter yields.
Alfalfa (Medicago spec.) plays an important role in feed production. Continuously flowering and rich in nectar, it is also an important food source for wild bees. Read on to learn everything about alfalfa cultivation and uses.
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Alfalfa: origin and properties
The species Medicago sativa is commonly known as alfalfa or lucerne. Other commonly cultivated types of alfalfa include sickle medick (Medicago falcata) and the hybrid sand lucerne (Medicago x varia). With origins in south-western Asia, alfalfa belongs to the Faboideae subfamily of the legume family (Fabaceae). Dating back to before 500 BC, it is the oldest cultivated plant grown exclusively for fodder. Apart from field cultivation, alfalfa can also be found growing wild on roadsides and field margins, in shrub borders, dry meadows and as a ruderal growing on semi-arid grasslands.
Cultivated alfalfa species are evergreen herbaceous perennials. Common alfalfa can grow up to 1m high and forms a taproot that reaches a depth of up to 4.5m. The survival buds are located at the surface of the soil or a few centimetres aboveground, so they overwinter as chamaephytes or hemicryptophytes. Alfalfa stems grow upright and branched with alternate, three-pinnate leaves. Alfalfa leaves are elongated−lanceolate to elliptical, and the leaf margins are usually serrated at the tip. The stem of Medicago sativa is also square and hairy. Alfalfa flowers are hermaphroditic and symmetrical, growing in clusters at the top of long stems. The flowers range in colour from violet to yellow to white and, with a decent supply of nectar, are enjoyed by bumblebees, wild bees and butterflies. The brown legumes of common alfalfa are hairy, form a spiral and contain 10 to 20 seeds. The smooth pods of sand lucerne alfalfa also form a spiral, but only contain 3 to 8 seeds. The seeds have a long shelf-life, are kidney-shaped and yellow-orange to light brown. Alfalfa seeds are ejected from their pods when the fruit ripens and are then spread by humans, animals and wind.
When does alfalfa bloom?
The flowering period for sand lucerne extends from June to August. Common alfalfa, on the other hand, continues to flower until September.
Green manure
As a legume, alfalfa can bind nitrogen from the air in its root nodules with the help of the soil bacteria Rhizobia. So, working alfalfa into the soil affords the following crop more access to nitrogen as the alfalfa decomposes. This makes alfalfa a suitable pre-crop for heavy feeders such as potatoes (Solanum tuberosum), Brassica plants, maize (Zea mays) and gourds (Cucurbita). In addition to improving the soil’s nitrogen levels, alfalfa improves soil structure thanks to its extensive root system that loosens up the substrate, which in turn protects against erosion. Alfalfa plants likewise serve as bee pastures as well as food for wild animals such as deer and hares, making it a great choice for green manure.
Growing alfalfa in the garden
Alfalfa prefers a warm and sunny location with chalky, well-drained, nutrient-rich soil. Deep loam or loess soils are suitable soil types. Avoid acidic compacted soils prone to waterlogging. Alfalfa plants grow best in soil with a pH value of 6.5 to 7.5. With its extensive root system, alfalfa copes better with a lack of water rather than too much, so soils should be dry to moderately moist. That being said, the crop has a high demand for water, so it is important the soil has good water storage capacity.
The sowing period for alfalfa is long, ranging from April to mid-August. If sown in spring, lucerne plants can develop enough to be ready to survive winter on their own. If starting your alfalfa seeds outside, check the soil temperature; the seeds need a soil temperature of at least 5 °C in order to germinate.
To prepare the soil for sowing alfalfa seeds, loosen it deeply and remove all weeds. Then sow the seeds to a depth of 1 to 1.5cm and press down lightly on the soil. We suggest using 25 to 30g of seeds per 10m². For large areas, simply spread the seeds over the soil’s surface, and then gently work the seeds into the substrate with a rake. Use the back of the rake to lightly press the soil down. Do not forget to water the seeds after planting them; from seeds to seedlings, keep the soil evenly moist. The first alfalfa seedlings should appear after about a week or two.
Tip: did you know that alfalfa can also be cultivated indoors on a windowsill or in the kitchen? Alfalfa sprouts are healthy and a refreshing way to refine dishes even in winter.
Alfalfa plant care
Once the root system has formed, alfalfa plants cope well with dry periods, so you can start to water significantly less once the seeds have germinated and grown a little. As for fertiliser, these plants have a high demand for potassium and calcium, so apply a potassium-rich fertiliser that contains calcium. We suggest using a slow-release granular fertiliser; one application in spring will supply your plants with nutrients for several months. As alfalfa gathers its own nitrogen from the air, avoid using a fertiliser that contains nitrogen.
It may be necessary to add lime to the soil to maintain or achieve the optimal pH value. To find out whether you need to lime your soil, test your soil’s pH value and your soil type in advance.
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As a fodder crop, alfalfa is usually grown as a 2 to 3 year crop in agriculture. Since the plant continues to grow after harvest, alfalfa can be harvested three to four times a year. The first harvest is at a height of about 10cm and takes place just after the end of the flowering period. To prevent alfalfa grown as green manure from reseeding, harvest the plants before their seeds mature. Then in autumn, simply work the alfalfa back into the soil. If your alfalfa was sown later in the year, you have the option of leaving it over winter and first harvesting it the following spring.
Alfalfa is hardy down to about -20 °C, so it can be cultivated as a perennial, the only exception being snail medick (Medicago scutellata). Do not sow alfalfa outdoors after mid-August, as young alfalfa plants are sensitive to low temperatures. Regarding crop rotation, you will need to leave a cultivation break of 4 to 6 years between cultivating alfalfa or other legumes.
Alfalfa harvest and use
As mentioned above, alfalfa can be harvested multiple times, depending on whether you are using it as feed or green manure. If you plan to grow alfalfa as green manure, consider using a mulch mower to harvest and shred the plants and a tiller to work them into the soil as a nutrient rich mulch. In agriculture, alfalfa is often used for ensiling or for pellet, briquette and bale production. It is also sometimes dried as hay, but it is less suitable for this. With a high protein and mineral content and excellent yield, alfalfa is a valuable forage crop, especially for horses. It is also well-suited for other animals such as cattle, chickens and rabbits.
Alfalfa sprouts, flowers and young leaves are also edible for humans. When harvesting seeds and growing your own alfalfa sprouts, timing is everything. You need to wait until the seed pods are brown and dry. However, if you wait too long, the pods will open and the seeds will disperse before you have a chance to collect them.
Alfalfa seeds are often spread along with clover species such as red clover (Trifolium pratense) and crimson clover (Trifolium incarnatum). See our article on crimson clover to learn more about its use as green manure and forage crop.
