Raising sweet corn in your backyard garden is easy if you provide the correct growing conditions: fertile soil, abundant sunlight and ample heat. If you sow your corn kernels before the threat of frost ends in spring, chances are the germinating seeds may be killed. Corn plants will grow slowly if soil temperatures are cold or there is little ambient heat or humidity. If the soil is sandy and low in nutrients, corn plants will grow slowly or look deformed and stunted. If you are experiencing a chilly or wetter-than-normal summer weather pattern, the corn plants may grow slowly no matter what.
Lay a single layer of black plastic from a roll or collection of large garbage bags on the soil in between the rows in the sweet corn patch, especially if the weather and soil are overly cool. This will absorb heat and warm the air and soil around the corn, even on cloudy, rainy days. Weigh down the plastic with some rocks to prevent the wind from blowing it away. Once there is lots of sunshine and temperatures above 70 degrees F., remove the plastic from the soil.
Test the soil moisture around the plants by sticking your finger into the dirt to a depth of about 1 inch. It should be evenly moist, causing soil particles to stick to your fingers. Add enough water to the patch with a sprinkling can or irrigation system if the soil feels dry until the top 8 to 12 inches of soil is moist, according to the University of Tennessee Extension Service. Repeat the watering as needed if natural rain is absent and when your touching of the soil reveals dryness. Aspire to keep the soil moist but never soggy.
Pull out weeds that grow in the corn patch, as these unwanted plants will compete for water and nutrients alongside the corn seedlings. Use a garden hoe to shallowly cultivate the soil between rows and hand-pull little weeds that are within 5 inches of the base of the corn plant. Corn roots are shallow, so don't cut them with the hoe blade.
Fertilize the corn plants once they reach between 12 and 18 inches in height, according to Colorado State University, which is roughly knee high. Apply a 2-inch layer or compost or well-cured manure to all areas of the sweet corn patch and water it in. Alternatively, use a well-balanced water-soluble fertilizer (10-10-10) product following label directions to provide a boost of nutrients to the garden soil.
Monitor the soil moisture and weed situation of your sweet corn patch through the remainder of the spring and summer. Repeat Steps 3 and 4 as needed, and re-apply compost or the water-soluble fertilizer product every four weeks until corn cobs develop on the plants.