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Corn Planting Calendar: Grain vs. Silage

Grain corn and silage corn start the same way in the spring but end up on different clocks in the fall. Planting date, hybrid maturity and harvest plan all have to fit together.

What soil temperature does corn need before planting?

Corn is a warm-season crop, and the calendar matters less than the ground. Extension agronomists commonly point to a soil temperature of around 50 degrees Fahrenheit as the point where germination can get going. University of Maryland Extension, writing about silage, uses that same figure and notes that in Maryland the soil typically reaches it in late April. That is a regional observation, not a rule for everyone.

Take the temperature yourself. Push a thermometer two inches into the seedbed in the morning, when the soil is coolest, and check it for several days in a row. A single warm afternoon does not tell you much. Also look at the forecast for the next few days, since a cold rain right after planting can slow emergence and stress the seedling.

• Check morning soil temperature at seed depth, not air temperature
• Look at the five-day forecast before the planter leaves the shed
• Wet, cold ground is a bigger risk than a slightly late start

When is the usual planting window for grain corn?

USDA NASS publishes usual planting dates by state, based on reporters across the country. In the October 2010 edition, the most active planting period for corn for grain in Iowa runs from late April to mid May, while Minnesota is similar, and Pennsylvania runs from about the second week of May to late May. Those are the dates when most of the acres typically get planted, not the earliest or latest dates that can work.

Treat these as a starting point for a conversation with your local extension office. Your own field may drain slower or faster than the state average, and recent decades may have shifted what is usual. Your last spring frost date is the other anchor. Corn that has emerged can usually recover from a light frost because the growing point stays below ground for a while, but you should confirm that with your extension agronomist for your conditions.

How is silage corn planting different from grain corn?

Silage is harvested as a whole plant, chopped green, so the target is the right whole-plant moisture for packing and fermenting, not a dry kernel. That changes how you pick hybrids and when you plant. Because harvest comes earlier than for grain, many growers have a little more room on the planting date, and some hybrids are sold specifically for silage use.

The NASS tables show this in practice. In Iowa, silage corn and grain corn share nearly the same most active planting window, but silage harvest begins in mid August while grain harvest begins in late September. In Washington, the NASS silage harvest window opens weeks before the grain window. Plan backward from the date you want the chopper running, then ask your extension dairy or forage specialist about hybrid maturity for your area.

• Match hybrid maturity to your frost-free season, not to the neighbor's choice
• Decide who is chopping and when before you pick a planting date
• A late-planted field often needs an earlier hybrid

How do you build a planting plan from your own frost dates?

Start with your average last spring frost and your average first fall frost, which you can get from your National Weather Service office or NOAA climate normals. Count the days between them. Zone numbers will not help here. The USDA Plant Hardiness Zone Map is based on winter minimum temperatures, so it says nothing about when to plant corn.

Next, ask your seed dealer or extension agronomist how many days or growing degree days your hybrid needs to reach black layer for grain or the right silage stage. Work backward from first fall frost, leave a cushion for a cool year, and you will see the latest date you can plant. For example, if your first fall frost usually falls in early October and the hybrid needs most of the season, a planting delay of two or three weeks may call for a shorter hybrid.

What are the common mistakes with corn planting dates?

The most common mistake is planting by the calendar because it is a nice day in April. A warm spell can fool you, and a cold snap that follows can leave seed sitting in cold, wet soil. The second is mixing fields: planting the full-season hybrid late on the field you hoped to chop for silage, then finding it is too wet at the first frost.

A third mistake is skipping records. Write down planting date, hybrid, soil conditions and emergence for every field. After a few seasons, your own notes will tell you more about your farm than any statewide average.

• Planting into cold, saturated soil
• Ignoring hybrid maturity when planting dates slip
• Not recording planting dates and emergence by field

Who should you ask about crop insurance and planting dates?

Crop insurance programs set final planting dates and, in some cases, earliest planting dates, and they can differ by crop and county. Talk to your crop insurance agent and read the USDA Risk Management Agency materials before you set your plan, and contact your local Farm Service Agency office about program deadlines. Those dates are about coverage, not agronomy, so keep the two questions separate.

Timing at a glance

Last reviewed: November 2026. Educational information, ranges only. Confirm timing with your county extension office.

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