Glass Gem
Zea mays
A distinctive presentation in fall displays, the glassy-looking kernels are unique to this variety. Kernels can be popped, but results may vary. Sturdy plants can reach 10' tall. Avg. ear size 6-8". Requires a fairly long growing season for favorable yields. Bred by the late Carl Barnes, an Oklahoma Cherokee who dedicated his career to reclaiming and preserving seed of traditional Native American corns.
Harvest
120d
Days to harvest
Sun
Full sun
Zones
2–11
USDA hardiness
Height
5-8 feet
Planting Timeline
Showing dates for Glass Gem in USDA Zone 7
All Zone 7 corn →Zone Map
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Glass Gem · Zones 2–11
Growing Details
Zone-by-Zone Planting Calendar
| Zone | Indoor Start | Transplant | Direct Sow | Harvest |
|---|---|---|---|---|
| Zone 3 | — | — | June – July | November – October |
| Zone 4 | — | — | June – July | October – October |
| Zone 5 | — | — | May – June | October – October |
| Zone 6 | — | — | May – June | October – November |
| Zone 7 | — | — | April – June | September – November |
| Zone 8 | — | — | April – May | September – October |
| Zone 9 | — | — | March – April | August – September |
| Zone 10 | — | — | February – April | July – September |
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
Freshly harvested Glass Gem ears should be dried further before storage. Remove husks immediately and spread ears in a single layer in a warm, dry, well-ventilated area for 2-4 weeks until kernels are completely hard and moisture content drops below 14%.
For long-term storage, keep whole ears in breathable containers like mesh bags or cardboard boxes in a cool, dry location. Properly dried ears remain viable for 2-3 years. Remove kernels from cobs just before use to maintain freshness.
To preserve as cornmeal, remove kernels using a corn sheller or by hand, then grind in small batches using a grain mill or high-powered blender. Fresh cornmeal should be stored in airtight containers in the refrigerator for up to 6 months, or frozen for longer storage. Many gardeners save the most colorful ears whole for ornamental use, as the stunning appearance is Glass Gem's primary appeal.
History & Origin
Origin: Mexico
Advantages
- +Disease resistance: Black Walnut
- +Edible: Edibile
- +Fast-growing
Companion Plants
Plant Together
Beans
Fixes nitrogen in soil that corn needs, part of the Three Sisters planting method
Squash
Ground cover suppresses weeds and retains moisture, completes Three Sisters guild
Nasturtiums
Trap crop for cucumber beetles and aphids that attack corn
Marigolds
Repels corn earworm moths and other harmful insects
Sunflowers
Attracts beneficial insects and provides natural windbreak for corn
Dill
Attracts beneficial predatory insects that control corn pests
Cucumber
Benefits from corn's nitrogen and corn provides natural trellis support
Radishes
Breaks up compacted soil and deters corn borers when planted nearby
Keep Apart
Black Walnut
Produces juglone toxin that severely stunts corn growth and development
Tomatoes
Both are heavy nitrogen feeders creating competition, and attract similar pests
Fennel
Allelopathic chemicals inhibit corn germination and growth
Nutrition Facts
Per 100g serving. % Daily Value based on 2,000 calorie diet. Source: USDA FoodData Central (FDC #168538)
Pests & Disease Resistance
Resistance
Good natural resistance typical of flint corns. More resistant than sweet corn varieties.
Common Pests
Corn earworm, birds (attracted to colorful kernels), European corn borer
Diseases
Common rust, smut, northern corn leaf blight (generally more resistant than sweet corn)