When To Plant Alfalfa

Plant alfalfa in early spring after the last frost date for your growing zone. Knowing exactly when to plant alfalfa is the single most important factor for a successful stand. Get the timing wrong, and you risk poor germination, weed competition, or winter kill.

This guide covers everything you need to know about planting alfalfa at the right time. We’ll break down the best seasons, soil conditions, and regional differences so you can make the smartest choice for your field.

Alfalfa is a cool-season perennial legume. It thrives when temperatures are moderate and moisture is reliable. The two main windows for planting are early spring and late summer. Spring is the most common choice, but fall planting works in certain climates.

Spring Planting: The Standard Choice

Spring is the go-to season for most growers. The goal is to plant as soon as the soil is workable and the risk of hard frost has passed. Soil temperature should be at least 40°F (4°C) at a 2-inch depth, with warming trends expected.

Plant after the last spring frost date for your zone.
Ideal soil temperature range: 40°F to 60°F.
Aim for 4 to 6 weeks of cool, moist weather after emergence.
This gives seedlings time to establish before summer heat.

Benefits of Spring Planting

Spring planting gives alfalfa a full growing season. Seedlings face less weed pressure because many weeds haven’t germinated yet. You also avoid the risk of winter injury on young plants.

Risks of Spring Planting

If you plant too early, a late freeze can kill tender seedlings. If you plant too late, summer heat and drought can stunt growth. Dry soils in late spring also reduce germination rates.

Fall Planting: A Viable Alternative

In regions with mild winters, late summer or early fall planting works well. The key is to plant early enough that alfalfa has 6 to 8 weeks of growth before a killing frost. This allows roots to develop enough to survive winter.

Plant 6 to 8 weeks before the first expected frost.
Soil temperature should be above 50°F at planting time.
Seedlings need at least 4 to 6 true leaves before dormancy.
Fall planting reduces spring weed competition.

Benefits of Fall Planting

Fall planting often means cooler temperatures and more consistent rainfall. Weeds are less active, and you can harvest a full crop the following spring. It’s a good option for northern areas with short springs.

Risks of Fall Planting

If you plant too late, seedlings may not survive winter. Early frosts can kill young plants before they harden off. Fall planting also increases the risk of soil heaving in freeze-thaw cycles.

Regional Planting Guidelines

Your location determines the best planting window. Alfalfa is grown across many climate zones, so timing varies significantly. Use these regional guidelines to fine-tune your schedule.

Northern Regions (USDA Zones 3-5)

In cold climates, spring planting is the only reliable option. Wait until soil temperatures reach 40°F and all frost danger has passed. This usually falls between mid-April and late May.

Plant from late April to early June.
Use early-maturing varieties for short growing seasons.
Consider a companion crop like oats to reduce weed pressure.
Fall planting is risky due to early frosts.

Central Regions (USDA Zones 6-7)

These areas have more flexibility. Spring planting works from March to May. Fall planting is possible from August to September, provided you have enough growing time before frost.

Spring: March to May.
Fall: August to mid-September.
Monitor soil moisture carefully in summer plantings.
Irrigate if needed to ensure good germination.

Southern Regions (USDA Zones 8-10)

In warm climates, fall planting is often preferred. Spring planting can work, but summer heat stresses young plants. Plant in October or November for a winter-growing stand.

Fall: October to December.
Spring: February to March.
Choose non-dormant varieties for mild winters.
Avoid planting during hot, dry periods.

Soil Preparation Before Planting

Good timing means nothing if your soil isn’t ready. Alfalfa needs well-drained, fertile soil with a pH between 6.5 and 7.5. Prepare your field at least 2 to 4 weeks before planting.

Test Your Soil

Get a soil test 3 to 6 months before planting. This gives you time to adjust pH and fertility. Alfalfa is sensitive to acidic soils, so lime may be needed.

Target pH: 6.5 to 7.5.
Apply lime 6 to 12 months before planting for best results.
Correct phosphorus and potassium levels based on test results.
Alfalfa needs high levels of both nutrients.

Control Weeds

Weeds compete with alfalfa seedlings for light, water, and nutrients. Control perennial weeds the year before planting. Use tillage or herbicides as needed.

Eliminate quackgrass, Canada thistle, and other perennials.
Use a burndown herbicide 2 weeks before planting.
Consider a stale seedbed technique: till, let weeds germinate, then kill them.
Plant into a clean, weed-free seedbed.

Prepare The Seedbed

Alfalfa seeds are small and need good soil contact. Prepare a firm, smooth seedbed. Avoid deep tillage that creates air pockets.

Use a cultipacker or roller to firm the soil.
Seed depth: 1/4 to 1/2 inch.
Deeper planting in sandy soils, shallower in clay.
Ensure good seed-to-soil contact for uniform germination.

Seed Selection And Inoculation

Choosing the right variety is as important as planting at the right time. Select a variety suited to your region and intended use. Inoculate seeds with rhizobium bacteria for nitrogen fixation.

Variety Selection

Consider dormancy rating, disease resistance, and winter hardiness. Non-dormant varieties grow in mild winters but may not survive cold climates.

Dormant varieties: Best for northern regions.
Non-dormant varieties: Best for southern regions.
Look for resistance to phytophthora root rot and anthracnose.
Choose varieties with high yield potential.

Inoculation

Alfalfa needs specific rhizobium bacteria to fix nitrogen. Inoculate seeds just before planting. Use fresh inoculant for best results.

Apply inoculant to moistened seeds.
Mix thoroughly and plant within 24 hours.
Store inoculant in a cool, dark place.
Inoculation improves nitrogen fixation and yield.

Planting Depth And Seeding Rate

Correct depth and rate ensure a uniform stand. Alfalfa seeds are small, so depth matters more than you might think. Too deep, and they won’t emerge. Too shallow, and they dry out.

Planting Depth

Plant seeds 1/4 to 1/2 inch deep. In sandy soils, go slightly deeper. In clay soils, go shallower. The goal is to place seeds in moist soil with good contact.

Ideal depth: 1/4 to 1/2 inch.
Maximum depth: 3/4 inch in sandy soils.
Minimum depth: 1/8 inch in heavy clay.
Use a drill with press wheels for uniform depth.

Seeding Rate

Seeding rate depends on your region and intended use. Higher rates for hay production, lower rates for pasture. Adjust for seed size and germination percentage.

Hay production: 15 to 20 pounds per acre.
Pasture: 10 to 15 pounds per acre.
Irrigated fields: 12 to 18 pounds per acre.
Dryland: 8 to 12 pounds per acre.

Post-Planting Care

After planting, your work isn’t done. Proper care during the first few weeks determines stand success. Monitor moisture, weeds, and pests closely.

Irrigation

Alfalfa needs consistent moisture during germination and early growth. If rainfall is insufficient, irrigate lightly. Avoid overwatering, which can cause damping-off disease.

Keep soil moist for the first 2 to 3 weeks.
Irrigate with 1/2 to 1 inch of water per week if needed.
Use light, frequent irrigation to prevent crusting.
Reduce irrigation once seedlings are established.

Weed Control

Weeds are the biggest threat to young alfalfa. Control them early with mowing or herbicides. Some herbicides are safe for alfalfa at specific growth stages.

Mow weeds when they are 4 to 6 inches tall.
Use post-emergence herbicides labeled for alfalfa.
Apply herbicides when alfalfa has 2 to 4 true leaves.
Consider a companion crop like oats for weed suppression.

Pest Management

Monitor for pests like alfalfa weevil and aphids. Young stands are more vulnerable. Scout weekly and treat if thresholds are exceeded.

Check for leaf damage and stunted growth.
Use insecticide only when necessary.
Encourage beneficial insects like ladybugs.
Rotate fields to reduce pest buildup.

Common Mistakes To Avoid

Even experienced growers make mistakes. Here are the most common ones when deciding when to plant alfalfa. Avoid these to improve your chances of a successful stand.

Planting too early in cold, wet soil.
Planting too late in hot, dry conditions.
Ignoring soil pH and fertility.
Using old or un-inoculated seed.
Planting too deep or too shallow.
Overlooking weed control before planting.
Failing to monitor moisture after planting.

Frequently Asked Questions

Can I Plant Alfalfa In The Summer?

Summer planting is risky in most regions. High temperatures and dry soils reduce germination. If you must plant in summer, irrigate heavily and choose a heat-tolerant variety.

What Happens If I Plant Alfalfa Too Late In Spring?

Late spring planting exposes seedlings to summer heat and drought. Growth may be stunted, and weeds can overtake the stand. You may also miss the first cutting in the planting year.

How Do I Know When The Soil Is Warm Enough For Alfalfa?

Use a soil thermometer at a 2-inch depth. Wait until the temperature reaches at least 40°F and is trending upward. A consistent forecast of mild weather is also a good sign.

Is Fall Planting Better Than Spring Planting?

It depends on your region. Fall planting works well in mild climates with long autumns. Spring planting is more reliable in cold regions. Both can succeed with proper timing.

Can I Plant Alfalfa After Corn Or Soybeans?

Yes, but plan ahead. Corn and soybeans leave residue that can interfere with seeding. Ensure the field is clean and free of herbicide carryover. Test soil pH and fertility first.

Final Thoughts On Timing

Getting the timing right for when to plant alfalfa is a balance of science and experience. Start with your region’s frost dates and soil temperatures. Then adjust based on your specific field conditions.

Remember that alfalfa is a long-term investment. A well-timed planting gives you a productive stand for 3 to 5 years or more. Take the time to prepare properly, and you’ll reap the rewards.

Monitor your stand regularly after planting. Address problems early to avoid costly losses. With the right timing and care, your alfalfa will thrive and provide high-quality forage for years to come.