Planting Timeline
Showing dates for Ambrosia in USDA Zone 7
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Ambrosia · Zones 4–10
Growing Details
Zone-by-Zone Planting Calendar
| Zone | Indoor Start | Transplant | Direct Sow | Harvest |
|---|---|---|---|---|
| Zone 4 | April – May | May – June | May – July | August – September |
| Zone 5 | April – May | May – June | May – July | July – September |
| Zone 6 | March – May | April – June | May – July | July – October |
| Zone 7 | March – May | April – June | April – July | July – October |
| Zone 8 | February – May | March – June | April – August | June – October |
| Zone 9 | January – May | February – June | March – September | May – November |
| Zone 10 | January – May | February – June | March – September | May – December |
Complete Growing Guide
Growing Ambrosia corn requires careful planning and attention to detail, but the payoff in sweetness makes every effort worthwhile. Start by selecting a site with deep, rich soil that drains well but retains moisture. Test your soil pH—Ambrosia thrives in slightly acidic to neutral conditions (6.0-7.0). Work in 3-4 inches of well-aged compost or manure before planting, as this supersweet variety is a heavy feeder that demands fertile soil.
Timing is critical for success. Wait until soil temperature consistently reaches 65-70°F before direct sowing—cold, wet soil will cause seeds to rot rather than germinate. In northern zones (3-6), consider starting seeds indoors in biodegradable pots 2-3 weeks before your last frost date to extend the growing season. Transplant carefully when soil warms, as corn roots are sensitive to disturbance.
Plant seeds 1-1.5 inches deep in blocks rather than single rows to ensure proper pollination. Space plants 8-12 inches apart in rows 30 inches wide. The block formation helps pollen from tassels reach silks effectively—poor pollination results in kernels missing from cobs. Maintain strict isolation of 250 feet from other corn varieties or stagger planting by two weeks to prevent cross-pollination, which reduces Ambrosia's signature sweetness.
Fertilize heavily throughout the season. Apply a balanced fertilizer (10-10-10) at planting, then side-dress with nitrogen when plants reach knee-high and again when silks appear. Water consistently, providing 1-1.5 inches weekly, especially during tasseling and ear development—uneven moisture causes poorly filled ears.
Avoid the common mistake of removing suckers (side shoots). Recent research shows they don't significantly reduce yields and may actually help the plant withstand wind. However, do hill soil around the base when plants are 8 inches tall to support the extensive root system and prevent lodging in storms.
Harvesting
Harvest Ambrosia corn at the precise moment of peak sweetness—typically 20-23 days after silks first appear. Look for brown, dried silks and plump ears that feel firm when gently squeezed. The kernels should be bright and glossy, appearing full to the tip. Perform the fingernail test: pierce a kernel with your thumbnail. Milky white juice indicates perfect ripeness, while clear juice means it's too early and thick, pasty contents mean you've waited too long.
Harvest early morning when sugar content is highest—corn converts sugars to starch throughout the day. Twist and pull ears downward in one smooth motion, or cut the stalk just below the ear with sharp pruners. Each stalk typically produces 1-2 harvestable ears. Check daily once the first ear is ready, as the harvest window for peak quality lasts only 3-5 days. Process or consume immediately for maximum sweetness, as even supersweet varieties begin converting sugars to starch within hours of harvest.
Storage & Preservation
Ambrosia's supersweet genetics allow it to maintain quality longer than standard corn varieties, but proper storage is still crucial. Keep unhusked ears in the refrigerator at 32-35°F with high humidity—wrap in damp paper towels or store in perforated plastic bags. Properly stored, Ambrosia retains excellent eating quality for 5-7 days, significantly longer than regular sweet corn.
For longer preservation, blanch whole kernels for 4 minutes, then freeze in portion-sized bags. The high sugar content makes Ambrosia exceptional for freezing—it maintains texture and sweetness remarkably well. Alternatively, pressure can whole kernel corn following USDA guidelines. Avoid dehydrating this variety, as the high moisture content makes it prone to spoilage, and drying destroys the tender texture that makes Ambrosia special. For best results, freeze corn at peak ripeness within 2-3 hours of harvest.
History & Origin
Ambrosia corn was developed by Syngenta Seeds (formerly Rogers Seed Company) in the 1990s as part of the supersweet corn revolution that began in the 1980s. This hybrid represents the culmination of decades of breeding work to create corn varieties with enhanced sweetness retention—addressing the age-old problem of corn losing its sugar content rapidly after harvest.
The variety was bred specifically for the shrunken-2 (sh2) supersweet gene, which allows kernels to contain 2-3 times more sugar than traditional sweet corn varieties. Syngenta's breeding program focused on combining exceptional sweetness with the visual appeal of bicolor kernels and improved disease resistance. The name 'Ambrosia'—referring to the food of the gods in Greek mythology—was chosen to reflect the corn's extraordinary sweetness.
Ambrosia gained popularity among both commercial growers and home gardeners throughout the 2000s, becoming a standard in the supersweet category. Its development marked a significant advancement in corn breeding, proving that enhanced sweetness didn't require sacrificing kernel texture or plant vigor.
Advantages
- +Exceptional sugar retention lasting 5-7 days in refrigeration compared to 1-2 days for standard sweet corn
- +Striking bicolor appearance with consistent yellow-to-white kernel ratio for visual appeal
- +Strong stalks with good lodging resistance in windy conditions
- +Superior freezing quality that maintains texture and sweetness after thawing
- +Good resistance to northern corn leaf blight and common rust reduces spray requirements
- +Tender kernel walls that don't become tough even when slightly overripe
- +Consistent ear fill from tip to base with minimal kernel gaps
Considerations
- -Requires strict isolation from other corn varieties to prevent cross-pollination and sweetness loss
- -Seeds are more expensive than standard sweet corn varieties due to hybrid genetics
- -Slower germination in cool soil compared to standard varieties—prone to rot below 65°F
- -Heavy nitrogen requirements increase fertilizer costs and maintenance
- -Susceptible to Stewart's wilt in areas with flea beetle pressure
Companion Plants
Plant Together
Beans
Fixes nitrogen in soil for corn, corn provides natural trellis for climbing beans
Squash
Large leaves suppress weeds and retain soil moisture, completes the Three Sisters planting
Marigolds
Repels corn earworm, aphids, and nematodes with natural compounds
Nasturtiums
Acts as trap crop for aphids and cucumber beetles, deters corn borers
Sunflowers
Attracts beneficial insects and birds that eat corn pests, similar growing requirements
Dill
Attracts beneficial wasps that parasitize corn borers and other harmful insects
Sweet Alyssum
Ground cover that attracts hover flies and other beneficial insects that control aphids
Parsley
Attracts beneficial insects like tachinid flies that prey on corn earworms
Keep Apart
Tomatoes
Both are heavy feeders competing for nutrients, corn earworm also attacks tomatoes
Black Walnut
Produces juglone toxin that inhibits corn growth and development
Fennel
Allelopathic properties inhibit corn germination and growth
Pests & Disease Resistance
Resistance
Good resistance to northern corn leaf blight and common rust
Common Pests
Corn earworm, European corn borer, birds, raccoons
Diseases
Stewart's wilt, gray leaf spot, southern corn leaf blight