Hybrid

Illini Xtra Sweet

Zea mays 'Illini Xtra Sweet'

A beloved yellow supersweet corn that has earned its reputation as one of the sweetest varieties available to home gardeners. This reliable performer produces ears packed with incredibly tender kernels that burst with concentrated sweetness and maintain their quality longer than standard sweet corn. A must-grow for corn lovers who want maximum sweetness and eating pleasure.

Harvest

85-90d

Days to harvest

📅

Sun

Full sun

☀️

Zones

2–11

USDA hardiness

🗺️

Height

5-8 feet

📏

Planting Timeline

Zone:

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Direct Sow

Harvest

Direct Sow

Harvest

Showing dates for Illini Xtra Sweet in USDA Zone 7

All Zone 7 corn →

Zone Map

Click a state to update dates

Illini Xtra Sweet · Zones 2–11

What grows well in Zone 7? →

Growing Details

Difficulty

Moderate

Spacing8-10 inches

SoilDeep, fertile, well-drained soil with excellent organic matter content

pH6.0-6.8

WaterHigh — consistent moisture needed

SeasonSummer

FlavorExtremely sweet with intense corn flavor and exceptional tenderness

ColorGolden yellow

Size8-8.5 inches long

Zone-by-Zone Planting Calendar

Zone	Indoor Start	Transplant	Direct Sow	Harvest
Zone 3	—	—	June – July	September – October
Zone 4	—	—	June – July	September – October
Zone 5	—	—	May – June	September – October
Zone 6	—	—	May – June	August – October
Zone 7	—	—	April – June	August – September
Zone 8	—	—	April – May	July – September
Zone 9	—	—	March – April	June – August
Zone 10	—	—	February – April	June – July

Complete Growing Guide

Light: Full sun (6 or more hours of direct sunlight a day). Soil: Clay, High Organic Matter, Loam (Silt). Soil pH: Acid (<6.0), Neutral (6.0-8.0). Drainage: Good Drainage. Height: 5 ft. 0 in. - 8 ft. 0 in.. Spread: 1 ft. 0 in. - 2 ft. 0 in.. Spacing: 12 inches-3 feet. Growth rate: Rapid. Maintenance: Medium. Propagation: Seed. Regions: Coastal, Mountains, Piedmont.

Harvesting

Color: Gold/Yellow. Type: Caryopsis. Length: > 3 inches. Width: 1-3 inches.

Garden value: Edible, Showy

Harvest time: Fall

Bloom time: Summer

Edibility: Edibile

Storage & Preservation

Illini Xtra Sweet's supersweet genetics help it maintain sweetness longer than standard varieties, but still harvest and process quickly for best quality. Store unhusked ears in the refrigerator immediately after harvest—they'll maintain good eating quality for 5-7 days versus 2-3 days for standard sweet corn.

For freezing, blanch whole kernels for 4 minutes or corn on the cob for 7-11 minutes depending on ear size, then ice bath and freeze. The high sugar content makes this variety excellent for creamed corn preparations that freeze well. You can also cut kernels from raw ears and freeze directly for cooking later. Dehydrating works well for this sweet variety—blanch briefly, cut kernels, and dry until leathery. Avoid canning due to the low acid content requiring pressure canning methods.

History & Origin

Origin: Mexico

Advantages

+Disease resistance: Black Walnut
+Edible: Edibile
+Fast-growing

Companion Plants

Plant Together

Bush Beans

Fixes nitrogen in soil that corn can utilize, classic Three Sisters companion

Winter Squash

Large leaves suppress weeds and retain soil moisture, completes Three Sisters planting

Pole Beans

Uses corn stalks as natural support while providing nitrogen fixation

Marigolds

Repels corn earworms, aphids, and other harmful insects with natural compounds

Nasturtiums

Acts as trap crop for aphids and cucumber beetles, attracts beneficial predatory insects

Sunflowers

Attracts beneficial insects and birds that control corn pests

Dill

Attracts beneficial wasps and ladybugs that prey on corn aphids and other pests

Sweet Alyssum

Attracts beneficial insects like hoverflies that control aphids and other corn pests

Keep Apart

Black Walnut

Releases juglone toxin that severely stunts corn growth and can kill plants

Tomatoes

Both attract corn earworms and share similar pest problems, increasing infestation risk

Fennel

Releases allelopathic compounds that inhibit corn germination and growth

Nutrition Facts

Calories

86kcal(4%)

Protein

3.22g(6%)

Fiber

2.7g(10%)

Carbs

19g(7%)

Fat

1.18g(2%)

Vitamin C

6.8mg(8%)

Vitamin A

0mcg(0%)

Vitamin K

0.3mcg(0%)

Iron

0.52mg(3%)

Calcium

2mg(0%)

Potassium

270mg(6%)

Per 100g serving. % Daily Value based on 2,000 calorie diet. Source: USDA FoodData Central (FDC #168538)

Pests & Disease Resistance

Resistance

Moderate resistance to northern corn leaf blight and common rust

Common Pests

Corn earworm, European corn borer, corn flea beetle, wireworms

Diseases

Northern corn leaf blight, southern corn rust, gray leaf spot, crazy top

Frequently Asked Questions

How long does Illini Xtra Sweet corn take to grow?▼

Illini Xtra Sweet takes 85-90 days from planting to harvest. Count on about 20-22 days from silk emergence to picking time. This longer season requirement means northern gardeners in zones 5 and cooler need to plant as soon as soil reaches 65°F and may struggle with early frost cutting the season short.

Can you grow Illini Xtra Sweet corn in containers?▼

Container growing isn't recommended for Illini Xtra Sweet due to its 6-8 foot height, extensive root system, and need for block planting to ensure pollination. Each plant requires about 1 square foot of space, and you need at least 16 plants for adequate pollination. Focus on dwarf varieties if container growing is your only option.

What does Illini Xtra Sweet corn taste like?▼

Illini Xtra Sweet delivers intense, concentrated sweetness with tender kernels that pop when bitten. The supersweet genetics create sugar levels 2-3 times higher than standard sweet corn, with a clean corn flavor that doesn't become starchy quickly. The texture remains creamy and tender even a few days after harvest.

When should I plant Illini Xtra Sweet corn?▼

Plant when soil temperature consistently reaches 65-70°F, typically 2-3 weeks after your last frost date. Supersweet varieties like Illini Xtra Sweet are more sensitive to cold soil than standard corn and will rot or germinate poorly if planted too early. Use a soil thermometer rather than guessing by calendar dates.

Why does my Illini Xtra Sweet corn need isolation from other varieties?▼

Cross-pollination from field corn, popcorn, or other sweet corn varieties will cause kernels to become starchy and lose their supersweet characteristics. The sh2 gene that creates extreme sweetness is recessive, so any cross-pollination immediately reduces sweetness. Maintain 250 feet distance or time plantings 2-3 weeks apart.

Is Illini Xtra Sweet good for beginners?▼

This variety is rated moderate difficulty due to its specific requirements for soil temperature, isolation, and consistent care. Beginners often struggle with the timing, isolation needs, and lower germination rates. Start with standard sweet corn varieties first, then move to supersweet types like Illini Xtra Sweet once you've mastered basic corn growing.