How to Grow Corn

Corn picked and eaten fresh is about as good as it gets in gardening. Some people get the pot of water boiling before they go pick it so they can eat it right away.

Corn also asks more of you than most crops. It takes space, water, and a lot of food, and each stalk gives you one or two ears. If you have one small raised bed, corn may not be the best use of it. If you have the room, fresh sweet corn is worth growing at least once.

Here’s what I’ve learned growing corn in my low desert garden, including what went wrong and what I changed.

Corn at a Glance

Where Should You Plant Corn?

Corn needs full sun. It also gets tall, so plant it where it won’t shade the rest of your garden as the season goes on. In my garden that means the north side of the beds, or a bed on its own.

Give corn at least 12 inches of soil depth. Roots are shallow but they spread, and shallow beds make an already top-heavy plant even easier to knock over.

How Do You Prepare Soil for Corn?

Corn is a heavy feeder, and it shows quickly when it isn’t getting enough. Work at least an inch of compost into the bed before planting. I add plenty of worm castings too. If you’re filling or refreshing beds, here’s how I choose soil for raised beds.

I don’t use much fertilizer on most crops, but I make an exception for corn. I use AgroThrive, a liquid organic fertilizer that’s easy to apply. Fish emulsion works well too.

Aim to feed about twice a month through the growing season. Start once plants are up and growing well, and keep going through tasseling and ear fill, when corn is using the most nitrogen.

I’ll be honest, I fed mine less often than that and still got a good harvest. Start with good soil and feed when you can. Corn is forgiving if the soil underneath it is rich to begin with.

Should You Start Corn From Seed or Transplants?

Direct seeding is the standard advice, and it works well when the soil is warm. Corn roots don’t like being disturbed, so seeds planted in place usually grow faster than transplants. If you need more information on how to direct sow seeds, read this guide.

Spring in the low desert is the exception. Our planting window opens before the soil warms up. I direct seeded corn right after our last frost date one spring and almost none of it came up. The soil was still too cold. I started over with transplants and they took off.

If you’re planting in spring and your soil is still cool, start corn in cells and move the plants out when they’re 2 to 3 weeks old, before the roots start circling. Keep the root ball intact and water them in right away.

For monsoon planting in late July and August, the soil is already warm. Direct seed then.

How Do You Plant Corn?

Sow corn seeds 1 inch deep and about 8 inches apart. For hot weather planting, like a monsoon planting in Arizona, plant seeds up to 2 inches deep so they stay in contact with cooler, moister soil.

Plant one seed per hole, but plant a few more than you need. It’s easier to pull out extras than to fill in gaps. If you sow two or three seeds in the same hole, space them so you can thin without disturbing the roots of the one you’re keeping.

Keep the soil moist until seedlings emerge. Birds love corn seedlings, so cover the bed with tulle or netting until plants are 4 to 6 inches tall.

For square foot gardening, plant 3 to 4 corn per square foot.

Growing corn in containers: use containers at least 12 inches deep, and plan on hand-pollinating. A few plants in pots won’t pollinate each other well. More on container gardening here.

When Should You Plant Corn?

Wait until the soil temperature reaches 60°F at a 4 inch depth. Corn seed sitting in cold soil rots instead of sprouting, and supersweet varieties are even fussier about it than standard sweet corn. Here’s how to check your soil temperature with a soil thermometer.

In the low desert of Arizona, plant from mid-February through March. Long-time Arizona farmers say March 1st is ideal. Plant again with the monsoons in late July through August.

In spring, our calendar window opens before the soil is ready. Mid-February soil in Mesa is often still in the 50s. If yours isn’t at 60°F yet, either use transplants or wait and plant in early March. Corn planted too late in spring runs into our extreme heat while it’s trying to pollinate, and that’s when you get poor kernel fill.

Our spring window is short, so I skip succession planting in spring and plant it all at once. In milder climates with a longer season, you can sow every two weeks for a longer harvest.

How Much Corn Do You Need to Plant?

Corn is wind-pollinated, and that changes how you lay it out. Plant corn in a block, not a long single row. A block at least 4 feet by 4 feet gives pollen a much better chance of landing on the silks. A single row of corn along a fence looks tidy and pollinates poorly.

Growing more than one variety? Sweet corn crosses easily, and cross-pollinated ears can be starchy or oddly textured. Keep varieties at least 25 feet apart, or stagger planting dates by at least two weeks so they don’t shed pollen at the same time.

I learned this one by accident. After my direct seeded rainbow corn failed to come up, I replanted the bed with Silver Queen transplants. Some of that rainbow corn must have sprouted later, because I ended up with a couple of cross-pollinated ears.

What Are the Best Corn Varieties to Grow?

In a hot climate, look for short days to harvest varieties. The faster corn finishes, the better your odds of getting it pollinated and picked before summer heat takes over.

• Sugar Pearl is what I grew in my Three Sisters beds. White, sweet, and productive.
• Ambrosia Sweet Corn is a tender, sweet bicolor corn with juicy white and yellow kernels.
• Bodacious Sweet Corn is a sweet, flavorful yellow corn with large, well-filled ears.
• My Fair Lady Corn is an early-maturing, productive bicolor with tender kernels and a sweet flavor.
• Strawberry Popcorn grows on 4 foot stalks with 2 to 4 ears per plant, and makes good popcorn.

How Much Water Does Corn Need?

Corn has shallow roots and needs steady water all season. Water deeply and less often rather than a little bit every day. Shallow daily watering keeps roots near the surface, and that’s how corn ends up stressed and floppy.

Water matters most when corn is tasseling. Water stress during pollination shows up later as gaps in the kernels.

Raised beds dry out fast in the heat. If you’re not sure whether your beds are getting enough, here’s how I water raised bed gardens.

You can overwater corn too. Yellowing lower leaves and stalled growth in soggy soil usually mean it’s getting too much, too often.

How Do You Keep Corn From Falling Over?

Tall stalks plus shallow roots means corn tips over in wind. This used to be my biggest frustration with corn. I’d end up staking nearly every stalk.

A few things help:

• Plant in a block. Plants shelter each other.
• Hill soil up around the base of the stalks as they grow. Corn puts out new roots from the buried stem, and those brace the plant.
• Stake the ends of the bed and run twine down each side to hold the whole block upright.
• Grow pole beans up the corn. The year I did this, most of my stalks stayed upright and I only had to stake a few. The bean vines tied the block together.

In the low desert, monsoon plantings almost always need staking. Those storms bring real wind.

Why is My Corn Missing Kernels?

Patchy ears are a pollination problem. Every silk connects to one kernel, and each silk has to catch pollen. Gaps mean some silks never got any.

Hand-pollinating is easy insurance. Collect pollen from several tassels and sprinkle it on the silks as soon as they emerge. Pay extra attention to plants on the outside edges of the block, since they get the least pollen from neighbors. Repeat once or twice over the next few days. Mid-morning is the best time, when pollen is shedding.

To check your work, peel back the husk on a test ear. Full, plump rows mean good pollination.

The year I grew corn with pole beans, I was out of town for most of tasseling and couldn’t hand-pollinate at all. Pollination still came in around 80%. A few ears were spotty, but most filled out well. Block planting does a lot of the work for you.

What Pests and Problems Should You Watch For?

Prevention works better than treatment with corn. Plant disease-resistant varieties, encourage beneficial insects, and rotate where you plant corn each year.

• Birds will pull up seedlings. Use netting or tulle until plants are 4 to 6 inches tall.
• Corn earworms feed at the tip of the ear. If they’ve been a problem before, put a few drops of mineral oil in the tip of each ear after the silks turn brown. Check leaves for small holes and spray with Bt weekly while new holes keep appearing.
• Cutworms can be knocked back by drenching the soil with parasitic nematodes a couple of weeks before planting.
• Whiteflies turn up on nearby beans more than on the corn itself. I’ve had them without any noticeable drop in production, and I didn’t treat. Learn how to get rid of whiteflies in this article.

One season I had no corn earworms at all, which was new for me. I also had ladybugs and lacewings all over that part of the garden. I can’t prove they’re connected, but I’m not arguing with the results.

When is Corn Ready to Harvest?

Start checking daily once the silks turn brown and dry. Ears should feel plump and full to the tip. Sweet corn is usually ready about three weeks after the silks first appear.

The reliable test: puncture a kernel with your fingernail. Milky juice means it’s ready. Clear juice means wait.

Corn starts converting sugar to starch the moment you pick it, so harvest early in the morning while it’s cool and keep it in the husk in the fridge until you cook it. Same day is best.

Growing Corn in a Three Sisters Garden

Corn, beans, and squash grown together is one of the oldest companion planting methods there is. Corn gives beans something to climb, beans fix nitrogen in the soil, and squash vines shade the soil like a living mulch.

I adapted it to my 4×8 raised beds with two rows of corn down the center, one pole bean at the base of each stalk, and squash along the sides. It worked better than I expected. The beans held the stalks upright, and I harvested corn, beans, and squash out of the same bed. If you’re ready to try it, learn how to grow beans and squash.

Full layout, varieties, and timing are in How to Grow a Three Sisters Garden in Raised Beds. If you’re gardening in containers instead, try a Three Sisters grow bag garden.

Corn stalks also make a good living trellis for cucumbers. More pairings in the cucumber companion planting guide.

Growing Corn FAQs

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