Check an Opening for Shade Before Purchasing Seed

Start an opening's evaluation with shade. Ohio State Extension calls for a minimum of four to six hours of direct sunlight daily on logging-road plots. At a latitude of 40 degrees north, trees 70 feet tall cast midday shade 80 feet long on October 15, reaching 115 feet by November 15. That extends beyond the depth of a square quarter-acre planting. Next consider acreage, layout and crops. Match crops to your sunlight measurements and the plants already growing nearby.

The Ohio State fact sheet ANR-61 describes logging roads as suitable planting sites "if there is direct sun for at least four to six hours each day". The sheet offers no method for measuring that daily total. Tree shade, however, can be estimated with geometry. For level ground, calculate a tree's midday shadow by dividing its height by the tangent of the solar angle above the horizon. The U.S. Naval Observatory calculated the solar-noon angles listed below; we calculated the corresponding shadow factors.

The factor begins at 0.30 for June 21, rising to 2.00 by December 21 at a latitude of 40 degrees north. A line of trees 70 feet tall consequently shades 21 feet of ground in June and 140 feet in December. Fieldwork does not require the table. Around midday, find a level spot and divide your shadow's length by your height. Use that quotient for any tree there. For trees 70 feet tall, the November 15 factor, 1.64, produces a shadow 115 feet long.

Take a square quarter-acre clearing with sides roughly 104 feet long, beginning directly beside trees 70 feet tall. At midday on November 15, the entire plot is shaded, even though shadows are shortest at that time. A square one-acre opening with a depth around 209 feet retains a sunny strip 94 feet deep. In G9493, Missouri Extension advises leaving 30 to 50 feet between a woodland-edge planting and the tree line to create a soft edge. Our calculations show that this gap also reduces the shadow reaching the crop by the same distance.

Hills deserved a check before taking the blame. Our unpublished pilot layer uses a bare-earth elevation model to estimate daily mean hours of direct sunlight from terrain alone over a period beginning October 15 and ending January 15. The pilot includes 54 counties: Illinois has 22, Ohio 12, Missouri 10, Wisconsin 7 and Indiana 3. Taking the median of each county's median gives 9.5 hours daily. Terrain by itself puts just 1.0% of the ground below a daily mean of 6.5 hours. The county with the greatest shortfall reaches 12.6%; three counties exceed 5%. We share only aggregate results. Trees and buildings are absent from this layer, while Ohio State's sunlight guidance specifies no season. These limits prevent a pass-or-fail judgment for an individual clearing. The results point to terrain as an uncommon cause of insufficient sun within these counties. Start by examining the trees along the opening with leaf-off aerial imagery or by measuring with a tape and your own shadow.

The property shares recommended by Ohio State and Missouri differ. Ohio State also provides two separate recommendations.

For a 160-acre property, those recommendations begin at 1.6 acres under the lower end of Ohio's intensive range and reach 8.0 acres under its 5% guidance.

Minimum acreage depends on purpose. Ohio State describes plantings from a quarter acre to a half acre as potentially ideal for hunting when plants receive sufficient sunlight. For late-winter food or cover, it calls for an acre at minimum. The sheet leaves unclear whether this acreage refers to the entire opening or just ground receiving sunlight. We use the sunny portion because the hunting discussion treats light reaching plants as critical. With that approach, the square one-acre clearing discussed earlier contains roughly 0.45 acre receiving midday sun on November 15. It meets the hunting guideline but falls below the feeding guideline. This measurement represents midday on a single date. It cannot predict the amount of forage produced or remaining through winter. Missouri links the tendency for smaller plantings to yield less forage to "browsing pressure and shading". Shade can be measured before seed goes into the ground.

According to Ohio State, logging roads oriented east to west provide ideal seeding sites because they receive more sunlight. Ohio State also notes that cutting back most tall trees within about 50 feet along at least one side might be necessary. Our calculations identify the southern edge for clearing because midday shadows enter from that direction. Fifty feet of clearing easily exceeds the 21-foot shadow those 70-foot trees cast in June, but covers less than half their 115 feet of shade in mid-November.

Layout affects edge length as well. Ohio State observes that narrow, elongated plots provide more edge than squares with the same acreage. Missouri favors large square or rectangular plantings in areas with high deer density to keep browsing from wiping out a thin plot before its plants take hold. For sunlight, stretch the clearing east to west while leaving enough depth northward from its southern boundary to extend beyond the shade. High deer density shifts the choice toward Missouri's larger square or rectangular layout. Consider that tradeoff before cutting a thin strip.

Our database contains county summaries from the Cropland Data Layer for 575 counties across Wisconsin, Ohio, Missouri, Kansas, Iowa and Illinois. Within the average county's mapped area, corn plus soybeans account for 36.0%, grass plus pasture for 22.7% and forest for 21.2%. Together, alfalfa, oats, rye and winter wheat average 3.4%, and 405 counties out of 575 fall below 2%.

Kansas breaks that pattern with 11.6%, including a 10.6% share from winter wheat. Missouri differs in another way. Each of its 113 counties falls below 2% for small grains, while corn plus soybeans occupy only 20.7%, compared with 35.9% forest. Timber therefore exceeds row-crop acreage in Missouri's average county. Identifying the cover beside an individual planting requires a property-level look, as explained in our guide to designing food plots on a map. Illinois and Iowa present a different picture. When row crops occupy 57% to 64% of a county and small-grain acreage is scarce, planting small grains supplies something underrepresented across the county. We draw that conclusion from county-scale cover, which cannot identify what grows in the adjoining field.

None of the pages we consulted links a species with a specific count of sunlight hours. Mississippi State calls crimson clover "moderately shade tolerant" and describes Ladino white clover as "mildly". Its comparison of yield and seed expense uses trials conducted at two stations for one or two years. A clearing qualifies when the sunny acreage calculated with the rule below is sufficient for its purpose. When both clearings qualify but one receives less light, the shade-tolerance description can guide seed selection for that spot. Never let a shade-tolerance description serve as a reason to plant an opening that does not pass the test. See our native browse guide for the role a plot plays alongside other food.

The shadow calculations apply to a level site at midday, with a straight line of trees bordering the southern side. Slopes, tilted trees, breaks in the line and partial canopy cover alter the result. Shade reaches farther during morning and evening hours. County shares from the Cropland Data Layer are means without weighting and use mapped area that includes inland water. We excluded the other-hay category: its average county share shifts from 1.24% in 2023 to 0.08% during 2024, while pasture increases from 20.12% to 22.65%. We could not establish why. The 2024 file also omits three counties in Wisconsin. The extension shares offer management advice; we have not tested those recommendations.

We judge a clearing's worth solely by the ground that remains sunlit at midday. Hunters should therefore measure the southern tree line before purchasing seed.

During the month when the plot will matter, measure around midday. Divide your shadow's length by your height for the shade factor. Multiply that factor by the southern tree line's height in feet, then deduct the distance between the trees and the planting. This gives shaded depth. Limit that depth to a minimum of zero and a maximum equal to the clearing's north-south depth. Deduct shaded depth from the full north-south depth to find sunny depth. Multiply sunny depth by the east-west width, measured in feet, then divide the product by 43,560 for sunny acreage. Use a quarter acre to a half acre as the hunting benchmark and an acre at minimum for late-winter food. A shortfall means clearing the southern edge or abandoning that opening. After it passes, examine the county's crop composition and select seed.