Page 4 of 5 of the Sweet Corn Guide

Sweet Corn Plant Care

Watering, Weeding, and Hilling

Author: Greg Baka

Gardening books list a handful of vegetables as being easy to grow. Besides the usual lettuce, radishes, beets, carrots, onions (from sets), snap beans, tomatoes and turnips, a favorite among many people - sweet corn - is usually easy to grow. Barring a disaster, most home gardeners should be able to produce enough corn to satisfy their household by mid to late summer. This article explains how and when to water, hill and hoe to get the best crop of sweet corn.

Watering Sweet Corn

watering corn with overhead sprinkler

As a member of the grass family, corn is a high-demand moisture crop that needs an inch of water each week. The goal is to keep the soil consistently near the 75% moisture content. With very sandy soil, a little more may be necessary. One inch of water should wet the soil to a depth of at least 5 inches.

Much of the watering done in small gardens is ineffective, if not injurious, for unless the water is applied properly, plants may become very shallow-rooted. The inch of water should be applied all at one time. It is particularly imperative not to water the corn patch by giving the entire area a sprinkling every night, for reasons detailed below (needs scroll to below).

See the moisture estimate chart in our corn-planting article if you are unsure if you are over- or under-watering. (link to moisture chart in corn planting article)

How Much Water Do Corn Plants Need?

When Plants Are Young:

Young plants need a steady supply of water for good root formation. Roots can grow deep. However, it is important to understand that more than 70 percent of the water used by the plant is received from the top of half of the root zone. For best results, moisture needs to be available to the plant in the 4 to 18 inch depth range.

When Silks Develop:

corn needs water when silks are clear Image Credit

The next critical stage for corn formation is when they are near or at the tassel stage. This is when the silks begin to develop. Corn silks are 90 percent water and need moisture to develop and then accept and deliver the pollen to each individual kernel to fill out the ear.

“If those silks get a little wilted, the pollen can’t travel down them, and you’ll get a missing kernel, and every missing kernel is a take away from your yield, whether you’re a silage grower or a grain grower or a grazing customer,” DuPont Pioneer agronomist Nicole Rasmussen said in a 2014 article for Western Producer magazine.

As a garden grower, yield may not be of monetary value, but we know the pride and enjoyment that come from picking and eating a perfect ear of sweet corn.

During Tassel Time:

“The thirsty crop will use six millimeters [about 1/4 inch] of moisture per day once plants reach the tassel stage, so producers need to keep up with their irrigation plans,” Rasmussen said.

This is the highest peak water demand for the crop when the kernels will fill out and become plump and juicy. Without adequate water available for your plants, kernels may be small and drier than prime eating consistency.

Where to Water Corn Plants

Corn can be watered by numerous means (see our list below), although it is best to water corn around the base of the plant and not from an overhead sprinkler once corn begins to tassel.

For seed to be produced, the pollen which is shed from the staminate flowers on the tassels must fall on the silk on the ears. Corn pollen is carried by the wind. It takes 24 to 48 hours from the time the pollen drops on the silk until the flower is fertilized and the kernels begin to grow.

If rain (or sprinkling) makes the pollen sticky so that it fails to be released from the tassels, pollination cannot occur and seeds will not develop. Each silk is attached to an embryo kernel on the cob and each one must have a pollen grain drop on it for the kernel to develop. Very often, a rainy day or ill-timed sprinkling is responsible for a long, bare tip on an ear of sweet corn.

Besides rinsing off or gumming up the pollen, watering from overhead can leave water standing on the ears. Most fungal diseases that develop on corn need a damp environment to grow.

Irrigation Tools

  • Overhead Sprinkler - Be sure to use a rain gauge with your sprinkler so that you know when you reach 1” of water on your garden. As mentioned above, do not use a sprinkler any time after corn tassels and silks appear.
  • Drip Irrigation - Drip irrigation equipment is readily available and can easily be installed by do-it-yourselfers. It also exceeds 90 percent efficiency whereas sprinkler systems are 50 to 70 percent efficient. Colorado State University Extension offers an online fact sheet about the pros and cons of drip irrigation.
  • soaker hose Image Credit
  • Soaker Hose - A soaker hose or a perforated tube delivers water directly to the root zone of a plant where it seeps slowly into the soil one drop at a time, dripping at just the rate that soil can absorb and hold moisture. explains how to use a soaker hose to a garden's best benefit. Although there is some expense at the onset, using a soaker hose will save money over time.
  • Garden Hose or Bucket - If using a hose or bucket, you should create a moat around each plant. The moat diameter should be the same as the sprawl of the corn stalk; generally, the size above the ground is similar to the spread of the roots underground. This is easily done by using a Grub Hoe to pull dirt from your paths around your plant, until the moat is at least 2- 3 inches tall. Then slowly fill the area inside the moat with water so the majority of it soaks down into the root area.

Tip: Mulching and hilling (scroll down to Hilling section) around plants helps slow the evaporation of water around your corn plants.

Weeding Sweet Corn

To learn about weeding the corn patch before planting your seeds, see our Easy Weeding Guide. Once planted, cultivation should be shallow and light, but constant until the tassels appear.

While plants are young, cut off the extra corn plants instead of pulling them to thin them to the required distance according to your plot, whether in rows or circles. (Link to previous article about how to plant corn seeds.) Use a sharp hoe in a sliding or scuffling movement, rather than chopping deeply, around the corn stalks, always pulling the tool toward the plant. In larger gardens, a wheel hoe saves much hand labor.

Grass and weed seedlings should be removed while they are still small, thus disturbing the corn plant roots as little as possible. Large weeds not only draw moisture that the crops should have, but also shade the young corn plants, further checking the growth and reducing yields. Gardeners who control weeds conscientiously find that each year the care of the garden is simpler.

Hilling Your Sweet Corn

What is Hilling?

hilling with a high arch wheel hoe

Hilling is pulling up soil to mound it around the base of a plant, and between the plants within a row. Since most of corn's roots at the surface of the soil, you can not weed close to the base of the plant with a hoe. Instead you bury the small weeds by putting soil over them. This blocks out the sunlight and kills the young weeds. Taller weeds will need to pulled or ignored.

Corn is also susceptible to being blown over in high winds. So one way to support the plants is to provide them a stronger base by scraping a "hill" dirt up around the plant once or twice a week until the corn begins to tassel.

One more advantage of hilling your sweet corn is that the extra soil acts as "soil mulch" to help the corn roots retain moisture between rains or watering.

How to Hill

You can hill with a grape hoe or garden hoe by loosening soil from the paths between plants, then scraping or dragging that soil into loose mounds around and between your corn plants.

You can also hill with a wheel hoe with a plow attachment. When corn is 5 inches or shorter you can use a conventional wheel hoe in a double wheel configuration and move the soil in from both sides of your row in a single pass. Once the corn is taller than 5 inches, then a single plow is used to hill from one side at a time, passing by both the left and right sides of your rows.

Another type of wheel hoe, called the Hoss High Arch Wheel Hoe, is designed to hill plants up to 15 inches tall. The plows can be adjusted wider than on regular wheel hoes so that you do not disturb the growing corn's root system.

Note on a mature corn plant that the roots are a similar diameter than the stalks. Also note how corn has roots that are above the ground. Keeping these roots under soil will help anchor the plant, as well as help retain the much-needed moisture. Most of the moisture is acquired in the top half of the plant’s root system.

Now that you know how to water, weed, and hill, in our next article we will tell you about pollination and fertilizer for a successful crop.

Click a page below to read the rest of our Sweet Corn Guide