When To Plant Alfalfa In Spring

Knowing when to plant alfalfa in spring is the single most important decision for a successful stand. Getting this timing right sets the stage for strong root development, better weed competition, and higher yields for years to come.

This guide will walk you through the optimal spring planting window, the soil and weather conditions to watch for, and the step-by-step process to get your alfalfa off to a thriving start. Let’s get into the specifics of spring alfalfa establishment.

The optimal time for spring alfalfa planting is as soon as the soil is “workable.” This classic advice is your best starting point. But what does “workable” really mean? It’s when the soil is dry and warm enough to prepare a proper seedbed without causing compaction or harming soil structure.

Planting too early into cold, wet soil is a common mistake. It can lead to slow germination, seed rot, and weak seedlings. Waiting too long, however, risks exposing young plants to summer heat and drought stress before their roots are deep enough to handle it.

Understanding Your Soil Temperature

Soil temperature is a more precise guide than calendar dates alone. Alfalfa seeds germinate best when soil temperatures at seeding depth (about ½ inch) reach a consistent 45°F to 50°F (7°C to 10°C).

You can use a simple soil thermometer to check. Take measurements for several days in a row, in the morning, to get an accurate average. Consistent warmth is key; a single warm day isn’t enough.

Too Cold (Below 45°F): Germination halts, seeds sit vulnerable to disease.
Ideal Range (45-65°F): Seeds germinate reliably and seedlings establish vigor.
Too Warm (Above 80°F): Can cause heat stress on seedlings and increased weed pressure.

The Role of the “Frost Heave” and Calendar Dates

In many regions, a good target is just after the last expected hard frost. Alfalfa seedlings can tolerate a light frost, but a hard freeze after emergence can be damaging. Check your local frost date averages as a general frame of reference.

For most of the northern U.S. and Canada, the spring planting window typically falls between mid-April and mid-May. In warmer southern climates, planting can often begin in late February or March. Always prioritize soil condition over the calendar.

Key Signs Your Soil is Ready for Planting

Before you head to the field, perform these simple tests:

The Squeeze Test: Grab a handful of soil from seeding depth. Squeeze it firmly in your hand. If it crumbles apart easily when you open your hand, it’s ready. If it forms a muddy ball or leaves significant moisture on your skin, it’s too wet.
Traffic Test: Walk across the field. If your footprints are deep and the soil seems to smear, it’s too wet for machinery. You risk creating compaction layers that will haunt the stand for its entire life.

Pre-Planting Preparation is Crucial

Success with alfalfa starts long before the seed goes in the ground. Proper site selection and seedbed preparation are non-negotiable for a perennial crop that will be in place for 3-5 years or more.

Site Selection and Soil Testing

Alfalfa requires well-drained soil. It will not persist in low, wet areas where water pools. A slight slope is ideal. A soil test is an essential first step you should complete the fall before planting. It tells you two critical things:

Soil pH: Alfalfa thrives in a pH of 6.5 to 7.0. If your soil is more acidic, you will need to apply lime according to your soil test recommendations. Lime takes months to react, so applying it in the fall gives it time to work.
Fertility Levels: The test will show your levels of phosphorus (P) and potassium (K). Alfalfa has high demands for these nutrients. Apply fertilizer as recommended to build soil fertility before planting.

Creating the Perfect Seedbed

A firm, fine, and weed-free seedbed is the goal. This ensures good seed-to-soil contact, which is vital for germination.

Control Existing Weeds: Use a non-selective herbicide or tillage to eliminate any existing vegetation. Perennial weeds like quackgrass are especially problematic in new alfalfa.
Till and Level: Work the soil to a depth of 4-6 inches to break up clods and create a fine texture. Remove large rocks and debris.
Firm the Soil: This is the step many gardeners skip. Use a cultipacker, roller, or even drag a heavy piece of fencing behind your tractor. The ideal seedbed is firm enough that your heel sinks in no more than ½ inch when you walk on it.

The Planting Process: Step-by-Step

Choosing the Right Seed

Not all alfalfa varieties are the same. Select a variety with a fall dormancy rating suited to your winter climate. A local seed dealer or extension agent can provide the best advice. Also, look for varieties with good disease resistance ratings for your area.

Seeding Rate and Depth

Getting the depth correct is critical. Alfalfa seeds are small and cannot push through crusted soil.

Seeding Rate: Aim for 15 to 20 pounds of pure live seed (PLS) per acre for a dense stand. For smaller garden plots, this translates to about ¼ pound per 100 square feet.
Seeding Depth: Plant no deeper than ¼ to ½ inch in heavy clay soils. In sandy, lighter soils, you can go to ½ inch, but never deeper. When in doubt, plant shallower.

Seeding Method

For larger areas, a drill with a press wheel seeder is ideal as it places seed at a consistent depth and firms the soil over it. For smaller plots, you can broadcast seed and then lightly rake it in, followed by rolling or tamping the area to ensure good contact. Irrigate lightly if possible to start germination, but avoid saturating the soil.

Early Care for Your Spring Alfalfa Stand

Weed Management in Seedlings

Young alfalfa seedlings are poor competitors. The first 60 days are crucial for weed control. Many growers use a herbicide specifically labeled for new alfalfa seedlings to control broadleaf weeds and grasses. Always read and follow label instructions carefully. Mowing can also be an effective tool to prevent annual weeds from shading the alfalfa and going to seed.

Scouting for Pests and Problems

Keep a close eye on your new stand. Look for signs of insect pests like leafhoppers or aphids, which can stress young plants. Also, watch for disease symptoms like damping-off. Good drainage and proper pH help prevent many disease issues from the start.

The First Harvest: Patience Pays

Resist the urge to harvest your spring-planted alfalfa too early. The plants need to focus energy on building a deep root system, not regrowing leaves after cutting. A good rule is to wait until the stand is in full bloom (about 10% bloom) for the first cutting. This typically occurs 60-70 days after planting. This delay ensures the root crowns are fully developed, guaranteeing a healthier, more persistent stand.

Common Spring Planting Mistakes to Avoid

Planting in Wet Soil: This causes compaction and poor seed-to-soil contact. It’s the number one cause of establishment failure.
Seeding Too Deep: Alfalfa simply cannot emerge from deep planting. Err on the side of too shallow.
Skipping Soil Tests: Guessing on pH and fertility often leads to a weak, thin stand that weeds invade quickly.
Using Old or Poor-Quality Seed: Always buy certified seed with a recent germination test. The extra cost is worth it for a multi-year crop.
Harvesting Too Soon: Let the plants reach full bloom before that first cut to ensure root reserves are built up.

FAQ: Spring Alfalfa Planting

Can I plant alfalfa in early spring?

Yes, but “early” is defined by soil conditions, not the calendar. Wait until the soil is workable and has reached at least 45°F at seeding depth. Planting in early spring into mud will cause more problems than it solves.

What is the latest you can plant alfalfa in the spring?

The latest safe date is about 6-8 weeks before the onset of consistently hot, dry summer weather in your area. The seedlings need time to develop a deep taproot before facing summer stress. In many areas, late May or early June is the absolute cutoff for a reasonable chance of success.

Is it better to plant alfalfa in spring or fall?

Both can be successful, but spring planting is often prefered in colder climates with harsh winters, as it gives seedlings a full season to establish before winter. Fall planting is excellent in milder climates but requires precise timing so plants have enough growth to survive winter.

How long does alfalfa take to grow from seed in spring?

You’ll see emergence in 7-10 days under ideal conditions (warm, moist soil). The plants will grow slowly at first, then more rapidly. The first harvestable crop typically comes about 60-70 days after planting, when the stand reaches full bloom.

Can I just broadcast alfalfa seed?

You can broadcast seed for small areas, but it is harder to control depth and achieve good seed-to-soil contact. For best results, broadcast and then lightly rake, followed by rolling or tamping the area firmly. Using a drill seeder is far more reliable for larger plots.

By following these guidelines on when to plant alfalfa in spring and paying close attention to soil readiness, you give your new alfalfa stand the strongest possible foundation. Careful planning and patience during establishment will reward you with a productive, resilient field that provides quality forage for many seasons to come. Remember, the extra time spent getting the timing and seedbed right is the best investment you can make in your alfalfa crop’s future.