Getting the timing right for when to plant alfalfa in the fall is one of the most critical decisions you will make for your stand. Planting alfalfa in the fall requires timing the seeding several weeks before the first hard freeze. This window allows the young seedlings to establish a robust root system without the stress of summer heat or winter cold.
Fall planting offers distinct advantages, including less competition from weeds and typically more reliable soil moisture. However, missing the ideal window can lead to winterkill and a failed stand. This guide provides clear, step-by-step instructions to help you succeed.
When To Plant Alfalfa In The Fall
The core principle of fall alfalfa planting is based on the “first hard freeze” date for your specific location. A hard freeze is generally defined as temperatures dropping to 28°F (-2°C) or lower for several hours. Your goal is to seed early enough so that plants reach the “crown” stage before this freeze occurs.
This crown, a thickened area at the base of the stem where new shoots originate, is key to winter survival. A well-developed crown stores energy and is more resilient to freezing temperatures. Planting too late means seedlings are too small and vulnerable.
Understanding Your Target Planting Window
For most regions in the United States, the target fall planting window is 6 to 8 weeks before the average first hard freeze. This timeframe provides the approximately 45 days of growth needed for proper crown development.
You need to determine two key dates for your farm or field. First, find your area’s average first hard freeze date. Your local cooperative extension service is the best resource for this precise information. Second, count backwards 6 to 8 weeks from that date to establish your primary planting window.
For example, if your average first hard freeze is around October 20th, your ideal planting period would be between late August and early September. This schedule gives seedlings the full growth period they need.
Regional Timing Guidelines
While the 6-8 week rule is universal, local climates create variations. Here is a general breakdown for major U.S. growing regions.
Upper Midwest and Northern States
In states like Minnesota, Wisconsin, and the Dakotas, the window is narrow and early. Aim for planting from early to mid-August. The first hard freezes come quickly here, so timely seeding is non-negotiable for success.
Great Plains and Transition Zone
For areas like Kansas, Nebraska, Missouri, and Illinois, the typical window falls from late August to early September. Soil moisture from late summer rains can be beneficial, but watch for extended hot, dry periods.
Southern and Southwestern States
In warmer climates like Texas, Oklahoma, and California, fall planting often occurs later, from mid-September through October. The primary goal shifts from avoiding an early freeze to allowing establishment before cooler winter temperatures slow growth, though a later frost is still a planning factor.
Key Factors That Influence Your Exact Date
Beyond the calendar, several on-the-ground factors can shift your ideal planting date by a week or more. You must assess these conditions each year.
- Soil Temperature: Ideal soil temperatures for alfalfa germination are between 65°F and 85°F. Use a soil thermometer at seeding depth. Planting when soils are too warm (above 90°F) can cause poor germination.
- Soil Moisture: Adequate moisture is critical for seed germination and early growth. Planting into dust or overly saturated soil will lead to failure. Ideally, you want a moist seedbed.
- Weather Forecast: Look at the 10-14 day forecast after your planned seeding date. Consistent, moderate weather is ideal. Avoid planting right before a forecasted heavy rainstorm, which can cause crusting or wash seeds away.
- Previous Crop: If you are planting after a small grain harvest, you may have an earlier window. After corn silage, timing is tighter. Account for the time needed to prepare a proper seedbed.
Preparing For Fall Alfalfa Seeding
Successful establishment begins long before the seed goes into the ground. Proper preparation sets the stage for a thick, healthy stand that can last for several years.
Site Selection And Soil Testing
Alfalfa requires well-drained soil to thrive. Avoid low-lying areas prone to standing water or ice sheets in winter, as these will smother and kill seedlings. A slight slope is often beneficial.
A comprehensive soil test is the most important step. Take samples 6-8 inches deep and send them to a reputable lab at least a few months before planting. This gives you time to amend the soil based on the results.
- pH Level: Alfalfa requires a soil pH between 6.5 and 7.0 for optimal growth and nutrient uptake. If your pH is below 6.5, you will likely need to apply lime. This is critical because lime can take months to fully react with the soil.
- Phosphorus and Potassium: These are essential for root development, winter hardiness, and overall yield. Follow soil test recommendations closely for P and K application rates before seeding.
Seedbed Preparation
A firm, weed-free seedbed is essential for good seed-to-soil contact. Alfalfa seeds are small and need to be planted shallowly; a loose, cloddy seedbed will lead to poor germination and uneven stands.
- Control existing weeds. Use a burndown herbicide or tillage to eliminate all vegetation. Perennial weeds are a major threat to new seedlings.
- Perform tillage operations (if needed) to create a smooth surface. Avoid over-tilling, which can destroy soil structure.
- Firm the seedbed. This is a step many people miss. The seedbed should be firm enough that your footprint is no deeper than half an inch. You can use a cultipacker, roller, or even tractor tires to achieve this firmness.
Seed Selection And Inoculation
Choosing the right seed variety is a long-term investment. For fall planting, prioritize winter-hardy varieties with a high disease resistance score. Check with your local extension agent for varieties proven to perform well in your area.
Always use fresh, pre-inoculated seed or inoculate the seed yourself just before planting. The rhizobium bacteria in the inoculant form nodules on the roots that fix atmospheric nitrogen, which is vital for the plant’s growth. This symbiotic relationship is essential for a productive stand.
The Planting Process: Methods and Depth
With your timing determined and your field prepared, it’s time to plant. Precision during this phase directly impacts stand uniformity and survival.
Choosing A Seeding Method
You have several options for getting seed into the ground, each with its own considerations.
- No-Till Drill: This is an excellent option, especially for erosion-prone fields. A no-till drill cuts through residue, places seed at the correct depth, and firms the soil around it in one pass. Ensure the drill is calibrated correctly for alfalfa’s small seed size.
- Conventional Drill: Used on prepared seedbeds, a conventional grain drill with a small seed box or grass seed attachment can work well. Check that press wheels are set to firm the soil over the seed.
- Brillion Seeder or Cultipacker: This system is highly effective for firm seedbeds. The seeder broadcasts seed, and the cultipacker following behind presses the seed into the soil.
Avoid broadcasting seed without incorporation, as depth control is nearly impossible and seeds are left exposed.
Critical Seeding Depth And Rate
This is where many plantings fail. Alfalfa seed must be planted shallowly.
- Seeding Depth: Plant seeds between 1/4 inch and 1/2 inch deep in most soils. In sandy soils, you can go to 3/4 inch. Never plant deeper than one inch, as the seedling cannot emerge from that depth.
- Seeding Rate: For a pure alfalfa stand, aim for 15 to 20 pounds of seed per acre. If using a nurse crop (like oats) or seeding with a grass, reduce the alfalfa rate to 12-15 pounds per acre. Higher rates can help compensate for less-than-ideal conditions but avoid excessive rates that lead to overcrowding.
Post-Planting Care and Winter Survival
Your work isn’t done once the seed is planted. Management in the weeks and months after seeding determines if your seedlings will survive the winter.
Early Seedling Management
The first few weeks are about ensuring germination and early growth. Monitor soil moisture. If conditions become dry after planting, a light irrigation can be the difference between success and failure, but avoid heavy watering that causes crusting.
Scout for weeds. While a clean seedbed minimizes pressure, some weeds will emerge. In the seedling stage, alfalfa is very non-competitive. Consult your extension service for herbicide options safe for seedling alfalfa, as choices are limited.
Preparing The Stand For Winter
The management of your young alfalfa in the late fall is crucial for winter survival. The plants should enter winter in a vegetative state, not actively growing tall.
Avoid any cutting or grazing in the fall of the seeding year. The seedlings need to build root reserves and develop that protective crown. Removing top growth before a hard freeze depletes energy stores and significantly increases the risk of winterkill.
Allow the alfalfa to go completely dormant naturally. A light frost will top the plants, which is normal and beneficial. The dead top growth can actually provide a small amount of insulation to the crown during the coldest months.
Assessing Winter Damage In Spring
After the winter, you need to evaluate your stand’s survival. Wait until spring green-up has begun, then check several random areas in the field.
- Look for new shoots emerging from the crown. Healthy crowns will be firm and have multiple buds starting to grow.
- Check for heaving. Freeze-thaw cycles can push crowns out of the soil. If more than 30% of plants are heaved, the stand may be compromised.
- Count stems per square foot. A healthy new seeding should have at least 20 to 25 stems per square foot in the spring. If counts are lower, you may need to consider thickening the stand or reseeding.
Common Mistakes To Avoid
Understanding common errors can help you steer clear of them and save time and money.
- Planting Too Late: This is the number one cause of fall seeding failure. If you miss the 6-8 week window, it is generally better to wait for a spring planting rather than risk almost certain winterkill.
- Poor Seedbed Preparation: Planting into a soft, lumpy, or weedy seedbed leads to uneven emergence and weak plants.
- Incorrect Seeding Depth: Planting too deep is a silent killer. Always check the actual depth in the field during planting, don’t just rely on drill settings.
- Skipping Inoculation: Assuming the soil has the right bacteria is a gamble. Always use inoculated seed for guaranteed nitrogen fixation.
- Fall Harvesting: Never take a cutting from fall-seeded alfalfa in the same year. This practice severely weakens plants before winter.
Frequently Asked Questions
What Is The Latest Date To Plant Alfalfa In The Fall?
The absolute latest date is about 40 days before the first hard freeze, but this is risky. The safe cutoff remains the 6-week mark. If you are within 4 weeks of a freeze, postponing until spring is the wiser choice, as seedling development will be insufficient.
Can You Plant Alfalfa In October?
In northern states, October is almost always too late for successful establishment. In warmer southern and southwestern regions, October planting can be feasible if soil temperatures are still adequate and the first frost is several weeks away. Always base the decision on your local freeze dates, not just the calendar month.
Is It Better To Plant Alfalfa In The Spring Or Fall?
Both seasons have pros and cons. Fall planting offers less weed competition and often better soil moisture, but carries winterkill risk. Spring planting gives a full growing season before winter but faces more weed pressure and potential summer drought stress. The best choice depends on your local climate, field conditions, and management style.
How Cold Can Alfalfa Seedlings Tolerate?
Well-established seedlings with a developed crown can tolerate temperatures down to the mid-20s°F for short periods. However, young seedlings with only a few leaves are very sensitive and can be killed by even a light frost. This is why the timing before a hard freeze is so critical for their survival through the winter.
What Should I Plant With Alfalfa In The Fall?
A small grain like oats or barley can be used as a “nurse crop” at a very low rate (1/2 to 1 bushel per acre) to provide some soil cover and erosion protection. However, it must not compete with the alfalfa. More commonly, alfalfa is seeded with a companion grass like timothy or orchardgrass for pasture or hay mixes. Ensure the grass species is also suitable for fall planting in your area.