The genotype is the real spec sheet. A cultivar’s name tells you almost nothing about how it will taste on day three in the refrigerator, or whether it needs a buffer zone from the corn planted next door. Clemson Cooperative Extension sorts sweet corn into three genetic types, normal sugary (su), sugary enhanced (se) and supersweet (sh2), and that single letter code predicts sweetness, storage life, and isolation needs far better than any variety name on a seed packet.
The Genotype Behind the Name
Normal sugary, written su, is the baseline gene that has been in sweet corn for generations. It converts sugar to starch fast once the ear is picked, which is why old-timers used to say you should have the water boiling before you walk out to the garden. Su varieties taste good fresh but fade quickest of the three types.
Sugary enhanced, or se, carries a modifier gene that slows that sugar-to-starch conversion. The ear stays sweeter longer on the counter and the kernels tend to be more tender, which is part of why se has become the workhorse category for home gardens and roadside stands alike.
Supersweet, labeled sh2, holds sugar the longest of the three. But that trait comes with a catch Clemson is direct about: “Varieties with the sh2 gene require isolation from standard sweet corn or the sweetness will be reduced.” Cross-pollination between an sh2 variety and a su or se neighbor produces starchy, tough kernels on the sh2 ear. Clemson does not publish a specific distance or a planting-date gap for this isolation, so treat it as a firm rule with the details left to your seed source.
Timing matters for all three types, but especially for sh2. Clemson’s guidance: “Do not plant before the soil temperature at the 4-inch depth is at least 50 F. Wait to plant extra-sweet varieties until soil temperatures reach 65 F.” That four-inch depth matters because the surface warms faster than the root zone, and a warm top inch can trick a gardener into planting two or three weeks too early.
Storage is where the genotype difference shows up on the plate. Clemson notes that “Sweet corn loses sugar from the kernel rapidly at high temperatures… Sweet corn can be stored under optimal conditions for about five days, but will lose sweetness with each day of storage.” That five-day figure is a ceiling under ideal cold storage, not a guarantee, and it applies differently by type: su corn loses its sweetness fastest, se holds on longer, and sh2 outlasts both in the refrigerator. That is the practical reason to pick a genotype based on how quickly you plan to eat what you grow.
Clemson’s Eleven Recommended Cultivars
Clemson groups its recommended sweet corn cultivars by kernel color, and each one carries a genotype label rather than a maturity date. No days-to-maturity figure is published in this list for any cultivar, so the genotype and color are what to compare here.
Yellow kernel varieties
- Golden Queen, su
- Iochief, su
- Bodacious, se
- Incredible, se
- Illini Xtra Sweet, sh2
White kernel varieties
- Silver Queen, su
- Silver King, se
- Argent, se
- How Sweet It Is, sh2
Bicolor varieties
- Ambrosia, se
- Honey ‘N Pearl, sh2
Notice the pattern: yellow offers the widest spread across all three genotypes, white leans older and more su-heavy with one modern sh2 entry, and bicolor skews toward the enhanced and supersweet end. If your goal is longest shelf life in the fridge, the sh2 entries in any color column are your candidates. If you’re eating the same day you pick, an su variety like Silver Queen or Golden Queen will taste just as good and costs less to isolate.
What the Label Won’t Tell You
Here’s what this list does not include, and why that gap matters. No days-to-maturity number is published for any of these eleven cultivars in Clemson’s guidance, so don’t expect to plan a harvest date off this page. Check the seed packet instead. Every packet lists a maturity range specific to that seed lot and growing region, and that number will vary year to year depending on the supplier’s stock.
The isolation rule for sh2 varieties has the same gap. Clemson states the requirement exists but gives no distance and no timing, no “25 feet” and no “two weeks apart,” despite how often those exact figures circulate online. Those numbers are folklore, not Clemson data. Your seed supplier’s own planting instructions are the source to follow for isolation distance, since recommendations can differ by variety and by how much drift risk the breeder is willing to accept.
One more distinction worth making clearly: ornamental variegated corn, the kind grown for its striped or multicolored leaves rather than its ears, is a different category of plant entirely. It is not part of this eating-corn list, and its genotype classification is irrelevant to sweetness or storage since it isn’t grown to be eaten. If a catalog groups it alongside sweet corn cultivars, that’s a merchandising choice, not a horticultural one.
Common questions
Does a higher price always mean a sweeter variety?
Not necessarily. Price often reflects seed production cost and demand rather than genotype. An su variety can cost less than an se or sh2 seed lot while still tasting excellent fresh from the stalk; the price tag doesn’t map cleanly onto the sweetness scale.
Can I plant su and sh2 varieties in the same garden?
Clemson’s guidance says sh2 varieties need isolation from standard sweet corn, which includes su and se types, or sweetness will be reduced. No distance is specified, so check your seed supplier’s isolation instructions before planting them near each other.
Why does my corn taste starchy a day after I picked it?
That’s the genotype at work. Sugar converts to starch fastest in su varieties, especially in warm weather, since heat speeds up the process. Refrigerating ears immediately and eating them within a day or two limits the loss, but su corn will never hold sweetness as long as se or sh2 types.
Is bicolor corn a genotype or just a color choice?
Color and genotype are separate traits. Bicolor simply means the ear carries both yellow and white kernels; it says nothing about whether the variety is su, se, or sh2. You still need to check the genotype label separately from the color description.