Ornamental · Fabaceae
Alfalfa
Medicago sativa
Settle the ground and its pH before sowing, and this deep-rooted legume will keep giving you cuttings for season after season.
Full sun
Every 7–14 days
60–70 days
USDA 3–9
Overview
Think of alfalfa as the steady backbone of forage growing: a deep-rooted perennial legume that growers harvest several times each season for hay. It sits in the pea family, and like its cousins it draws its own nitrogen out of the air using Rhizobium bacteria tucked into the nodules on its roots. The taproot reaches a remarkable distance downward, which is exactly why a healthy stand brushes off dry spells and returns faithfully year upon year.
Where alfalfa does ask for some attention is the ground beneath it. It longs for deep, well-drained, near-neutral soil and grows unhappy on sour, waterlogged, or thin sites. Settle the pH and the drainage before you sow and the crop thanks you for years to come, and if you happen to miss the mark the stand will only thin a little while you put it right. Through summer it sends up purple to blue-violet pea flowers, although most growers gather their forage well before the blooms take charge.
It is also a plant that remembers where it has been. A worn-out stand turns the soil against its own seedlings, a quirk known as autotoxicity, so you simply cannot sow straight back into a tired field and expect much. Slot alfalfa into a rotation instead, and the crop that follows gets a lovely head start from the nitrogen left waiting in the ground.
Care
The short version: give it bright, open sun and deep, well-drained, near-neutral soil at a pH of 6.5 to 7.5. Coat the seed with inoculant, soak the bed thoroughly but not too often once roots have caught hold, and harvest on a steady rhythm right through the season.
Light
Alfalfa thrives on full sun and really has no patience for shade, so don't fret about giving it too much light. Bright, open ground bathed in sun all day is precisely what fuels the strong regrowth you want between cuttings.
Water
Once the deep taproot has settled in, alfalfa turns very drought tolerant, so the kindest approach is a thorough soaking only every 7 to 14 days rather than frequent little sips. Over a season it asks for roughly 10 to 12 inches of moisture, yet it truly can't cope with flooding or soggy ground, so good drainage counts every bit as much as the watering does.
Soil
You are most of the way there once you offer it deep, well-drained, fertile loam and keep the pH between 6.5 and 7.5. It struggles on sour, very alkaline, wet, or shallow ground, and that preference about the seedbed turns out to be the one thing that most decides whether a stand thrives.
Temperature
Alfalfa is wonderfully sturdy at both extremes, coping with a span of roughly -20°F to 95°F (-29°C to 35°C) across its hardiness zones. That hardiness against cold is just what carries the winter-tough types through northern winters so they greet you again each spring.
Humidity
Everyday outdoor humidity is nothing to worry over with a field crop such as this. What really earns your attention is air movement and drainage, because still, damp pockets are what tempt the root rots and white mold to settle in.
Feeding
Being a legume, alfalfa makes its own nitrogen through Rhizobium nodules the moment the seed is inoculated, so there's no need to feed it any. What it does appreciate is phosphorus, potassium, and lime applied by soil test to hold the pH close to neutral, both as it establishes and again after cuttings.
Pruning
Cutting is really the heart of growing this crop, so don't be shy about it. Gather that first harvest from a direct-seeded stand around 60 days after seeding, then keep to a steady cutting rhythm through the season for hay or forage.
Repotting
none
Size & spacing
A grown stand reaches about 24 to 35 inches (60 to 90 cm) tall, with plants reaching out 12 to 24 inches (30 to 60 cm) sideways. Since you broadcast or drill it as a field crop instead of setting each one out like a garden plant, you tend it as one thick stand rather than fussing over individuals.
When to plant
You will plant alfalfa straight into the ground from seed rather than raising transplants, and that keeps things simple. Drop the seed into a settled bed in spring or come back to it in late summer, gather your first cutting roughly 60 days on, and keep harvesting through the warm stretch as those purple blooms rise and fade.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Not typical; direct sown in field
- Plant: Spring (April-May) or late summer (late July-early September) into a firm, well-drained seedbed at neutral pH
- Harvest: Purple to blue-violet pea flowers in summer (May-October depending on latitude); cut for hay or forage multiple times per season
Hardiness
USDA hardiness zones: 3–9
Temperature: down to -40°C
Troubleshooting
Take heart: nearly every alfalfa hiccup traces back to the soil or the seedbed, where weak ground and the leftover chemistry of an old stand quietly cause harm before anything shows up top. Later, leaf-feeding pests arrive. Find the picture that matches yours and step in while the stand still has plenty of bounce-back left.
When a stand comes in patchy or just won't settle
Alfalfa can be picky about where it lives, and a struggling stand almost always points to ground that is too sour or too wet. When the soil turns acidic, the Rhizobia that nourish the plant simply doze off, while sitting water rots the roots and lifts crowns through winter. The good news is it's all fixable: lime the ground toward neutral well ahead of sowing, settle on a deep, well-drained field, and coat the seed so the roots can nodulate the way they should.
Fix:
- Lime acidic soils to pH 6.5-7.0 at least six months before seeding if pH is below 6.2
- Select deep, well-drained fields and avoid hilltops, eroded ground, and low spots where water pools
- Inoculate seed with the correct Rhizobium and ensure good seed-to-soil contact in a firm seedbed
A reseed back into old ground sprouts thin and small
This one is autotoxicity, and plenty of growers get caught by it, so you are in good company. A settled alfalfa stand puts out compounds that keep its own seedlings from sprouting and growing, which leaves a fresh sowing right back into the old field looking sparse, well short of the 25 plants per square foot you are after. Just shift to corn or a grass for at least a year before bringing alfalfa back, and let that rotation crop happily soak up the leftover nitrogen.
Fix:
- Do not reseed alfalfa directly back into an old alfalfa stand
- Rotate to a non-alfalfa crop such as corn or a grass for at least one year before returning to alfalfa
- Use the residual nitrogen from the old stand for the rotation crop
Plants drooping pale with crowns starting to give way
A handful of diseases creep in as a gradual stand decline, and wet ground brings out the worst of the bunch. Phytophthora and Aphanomyces root rots turn roots brown in soggy fields, bacterial wilt leaves plants short and yellow-green, and Sclerotinia drapes the crowns in fluffy white mold. You can stay ahead of it: set out resistant cultivars, sort out the drainage, and rotate away from alfalfa to thin down the inoculum waiting in the soil.
Fix:
- Plant disease-resistant cultivars (bacterial wilt, Phytophthora, Aphanomyces resistant)
- Improve drainage and avoid wet, low fields
- Rotate away from alfalfa to reduce soilborne inoculum
Leaves looking nibbled and the planting going thin
Three pests cause most of this, and each is manageable once you spot it. Alfalfa weevil larvae nibble and skeletonize the tender new growth, the potato leafhopper scorches the leaf edges yellow in what books call hopperburn, and aphids tag along behind. Run a sweep net through the field to learn what's actually present, treat once the numbers pass the economic threshold, and cut early or choose leafhopper-resistant cultivars to keep yourself ahead of the trouble.
Fix:
- Scout regularly and treat at established economic thresholds
- Use early or timely cutting to disrupt pest cycles
- Plant potato-leafhopper-resistant and pest-resistant cultivars where available
Toxicity
You can breathe easy here: alfalfa is gentle and safe right through, and it has never landed on the ASPCA toxic-plant lists. Folks enjoy it as sprouts and supplements, and it nourishes cats, dogs, rabbits, horses, and poultry with no trouble at all. The single thing to keep an eye on is grazing cattle and sheep, where a thick, leafy stand can spark bloat, so the answer is steady pasture management, not worry.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Alfalfa poses no danger to cats, and it has never shown up on the ASPCA poison lists. A curious little nibble does no more than an ordinary blade of grass would.
Dogs None
Dogs are perfectly fine around alfalfa. Dried alfalfa even appears as an ingredient in certain pet foods, so there is truly nothing here they need to steer clear of.
Horses Safe
Horses tuck into alfalfa as a rich hay and digest it nicely. It ranks among the more nourishing forages you can set in front of them.
Rabbits Safe
Alfalfa is a mainstay of many rabbit diets and a treat they adore. Younger rabbits especially flourish on it.
Livestock Mild
Cattle and sheep graze alfalfa safely, with just one thing worth keeping in mind. A leafy, pure stand can trigger frothy bloat that puffs up the left flank, and fresh growth now and then sets off photosensitization. Hold the legume to roughly a third of the pasture, offer hay before turnout, and don't send hungry animals onto a heavy stand.
Birds Safe
Birds come to no harm eating alfalfa, and poultry happily take it as a green feed.
People Safe
People enjoy alfalfa as well, most often in the form of sprouts or a dried supplement. The plant holds no toxins that would make it unsafe.
Not poisonous to cats, dogs, or people. The only real caveats are with grazing ruminant livestock: lush alfalfa can cause frothy bloat in cattle and sheep grazed heavily, fresh alfalfa can rarely cause photosensitization, and alfalfa contains phytoestrogens. Limit legume to about 30 percent or less of pasture, feed hay before turnout, and avoid turning hungry animals onto lush stands.
Varieties
Alfalfa types mostly differ in how far they slow down come autumn and which diseases they shrug off. Here are the differences worth tucking away before you pick out your seed.
Fall-dormant (winter-hardy northern) types, FD 2-4
A low fall-dormancy score has these types easing off growth early and weathering hard winters, which is just what you'll want in chilly northern ground.
Non-dormant (southern) types, FD 8-9
Carrying a high fall-dormancy score, these keep growing well into the season for warm southern regions, though they trade away some winter hardiness to do it.
'Alfagraze'
Developed to withstand the wear of grazing, this cultivar grew into the yardstick that grazing-tolerance trials use to judge the rest.
Disease-resistant modern cultivars
These fresher lines pile up resistance to bacterial wilt, Phytophthora and Aphanomyces root rots, Fusarium wilt, anthracnose, and the potato leafhopper.
Companions
Plant near
Grasses (orchardgrass, timothy): Grass-alfalfa mixtures reduce frothy bloat risk in grazing ruminants and improve stand productivity.
Corn or other rotation crops following alfalfa: Rotating to a non-alfalfa crop for a year uses alfalfa's residual nitrogen and avoids autotoxicity when returning to alfalfa.
Keep apart
New alfalfa seeded into an existing alfalfa stand: Autotoxicity from the established alfalfa inhibits germination and growth of the new alfalfa seedlings.
How to propagate
You raise alfalfa from seed dropped right into the field, and honestly the sowing is the easy part. What really decides things is preparing the bed, coating the seed, and planning the rotation with a little care.
SeedModerate
Spring (April-May) or late summer (late July-early September) · About 60 days to first harvest; full stand establishes over the seeding year
You sow alfalfa directly, never starting it indoors, either in spring around April to May or through late summer from late July into early September. Begin by coating the seed with the proper Rhizobium so it can make its own nitrogen, then tuck it in a quarter to half an inch deep, going a touch deeper in sandy ground, within a firm, well-drained, near-neutral bed. A first cut is yours about 60 days in, while the full stand fills out across the rest of the seeding year. One steady rule keeps everything on track: never drop alfalfa straight back into an old alfalfa field, or autotoxicity will undo the new stand.
Myths
People often worry that alfalfa is poisonous and risky to feed to animals or to people.
Alfalfa is a safe, nourishing forage that growers feed to livestock and rabbits, that people take as a supplement, and that shows up in some pet diets, and it has never landed on the ASPCA toxic-plant lists. The only real thing to watch is frothy bloat in cattle and sheep moved onto a leafy stand, alongside the rare case of photosensitization and a touch of phytoestrogen content. None of that turns the plant poisonous to pets or people, so you can relax about it.
Sources
- USDA Forest Service FEIS
- University of Minnesota Extension
- University of Minnesota Extension
- University of Wisconsin-Madison Extension (Team Forage)
- University of Kentucky
- UC ANR Statewide IPM Program
- UC ANR Statewide IPM Program
- Penn State Extension
- ASPCA
- University of Kentucky
- USDA SARE
- University of Kentucky Master Grazer