If you’re planning your Pennsylvania garden, knowing when to plant corn is the first step to a successful crop. For optimal harvest timing, you need to sync your planting date with the last spring frost and your local climate.
Planting too early risks losing seeds to cold, wet soil. Planting too late can push your harvest into fall’s unpredictable weather. This guide will help you hit that perfect planting window for sweet, full ears.
When to Plant Corn in Pennsylvania
For most of Pennsylvania, the best time to plant corn is from late April to mid-May. The ideal soil temperature for corn germination is a consistent 55°F (13°C) or warmer, measured at a 2-inch depth in the morning.
This timing usually falls 1-2 weeks after the average last spring frost date for your area. Corn is very sensitive to frost; a late cold snap can wipe out young seedlings. Waiting for warm soil ensures faster germination and stronger starts.
Understanding Pennsylvania’s Climate Zones
Pennsylvania’s varied landscape means frost dates differ. Here’s a general breakdown:
- Southwestern & Southeastern PA (Zones 6b-7a): Earlier last frosts (late April). Aim for planting between April 20th and May 10th.
- Central PA (Zone 6a): Last frosts typically occur in early May. Target May 1st to May 20th for planting.
- Northern Tier & Mountainous Areas (Zones 5b-6a): Later frosts (mid-to-late May). Wait until between May 15th and June 1st to plant.
Always check your specific county’s average last frost date from a reliable source like your local extension office.
Soil Temperature is Your Best Guide
Calendar dates are helpful, but soil temperature is the real key. Use a simple soil thermometer.
If the soil is below 55°F, seeds will rot or sit dormant. At 55-60°F, germination may take 10-14 days. At 65°F or above, seeds sprout in just 5-7 days, giving you a vigorous start.
Planning for Your Desired Harvest Date
Think backward from when you want to eat your corn. Check the “days to maturity” on your seed packet.
- Early varieties: 60-75 days
- Mid-season varieties: 80-85 days
- Late-season varieties: 90-100+ days
For a late July harvest in central PA, plant an 80-day corn around May 5th. Count backward from your first expected fall frost to ensure late-maturing corn has enough time.
Step-by-Step Planting Guide for Success
1. Choosing the Right Corn Variety
Select varieties known to perform well in the Northeast climate. Consider these types:
- Sugar Enhanced (se) or Supersweet (sh2): For extra sweetness and longer shelf life.
- Standard (su): Classic sweet corn flavor, but sugar converts to starch quickly after picking.
- Heirloom & Open-Pollinated: Good for saving seeds and often excellent flavor.
Popular choices for PA include ‘Silver Queen’ (white, late), ‘Bodacious’ (yellow, mid), and ‘Luscious’ (bi-color, early).
2. Preparing Your Garden Bed
Corn is a heavy feeder and needs full sun (at least 8 hours).
- Soil: Work in 2-3 inches of compost or well-rotted manure a few weeks before planting.
- Fertilizer: At planting, use a balanced organic fertilizer or one higher in phosphorus to encourage root growth.
- pH: Aim for a soil pH between 6.0 and 6.8. A simple test kit can confirm this.
3. The Planting Process
Follow these numbered steps for best results:
- Wait for the correct soil temperature (55°F+).
- Plant seeds 1-1.5 inches deep in heavy soil, 1.5-2 inches deep in sandy soil.
- Space seeds 9-12 inches apart within a row.
- Space rows 30-36 inches apart to allow for growth and pollination.
- Water the seeds in thoroughly after planting.
For a continuous harvest, plant a block of the same variety every 10-14 days until early July. Don’t mix different corn types too closely unless they have similar maturity dates, to avoid cross-pollination which can affect flavor.
4. Care Through the Season
Consistent care prevents problems and boosts yield.
- Watering: Corn needs 1-1.5 inches of water per week, especially during tasseling and silking. Water at the soil level, not overhead.
- Weeding: Weed carefully when plants are young. Corn has shallow roots that can be easily disturbed.
- Fertilizing Again: Side-dress with a nitrogen-rich fertilizer when plants are about 12 inches tall, and again when they start to tassel.
- Pest Watch: Keep an eye out for corn earworms and raccoons. For earworms, apply a few drops of mineral oil to the silk tip once its browns.
Common Mistakes to Avoid
Planting in Cool, Wet Soil
This is the number one error. Impatient planting leads to poor germination and disease. Let the soil warm up and dry out a bit.
Planting in a Single Row
Corn is wind-pollinated. Plant in blocks of at least 4 rows side-by-side, not one long row. This ensures the pollen from the tassels can reach the silks on neighboring plants.
Ignoring Crop Rotation
Never plant corn in the same spot two years in a row. It depletes specific nutrients and encourages pests. Rotate with legumes like beans or squash.
Harvesting Too Late
For peak sweetness, harvest when the silks are brown and dry, the ears feel plump, and a pierced kernel releases a milky juice. If the juice is clear, its not ready. If doughy, its past prime.
FAQ: Your Pennsylvania Corn Questions Answered
Can I plant corn in early April in PA?
It’s generally too risky. Soil is cold and frost is likely. Unless you use protective cold frames or specialized row cover, wait until late April or May.
What happens if I plant corn too late?
Late-planted corn may not mature fully before the first fall frost, resulting in stunted, underdeveloped ears. It also faces higher pest pressure in late summer.
How long does it take for corn to grow in Pennsylvania?
From planting to harvest, it takes 60 to 100 days depending on the variety you choose. Always refer to the “days to maturity” on your specific seed packet.
Can I grow corn from store-bought ears?
It’s not recommended. Most commercial corn is hybrid, and seeds won’t produce true to the parent. They also may be treated with chemicals not for home gardening. Buy seeds from a reputable garden supplier.
What are good companion plants for corn in my PA garden?
The classic “Three Sisters” combo works great: plant pole beans and squash around your corn. The beans fix nitrogen, the squash shades out weeds with its broad leaves. Avoid planting tomatoes or cabbage too close to corn.
Timing your corn planting correctly in Pennsylvania sets the stage for the entire growing season. By focusing on soil temperature, frost dates, and variety selection, you give your crop the best possible start. Remember to plant in blocks for good pollination and provide consistent water during dry spells. With this plan, you’ll be on track for a summer harvest of sweet, homegrown corn that’s worth the wait. There’s nothing quite like the taste of corn picked fresh from your own garden and cooked within minutes.