Hi there, first time poster. Zone 6a (4/20 - 10/12 estimated growing season).
For the life of me I can’t find anywhere on the internet/forums/videos what people mean by “days of maturity” for POPCORN-type corn specifically and what days after germination popcorn tassels/silks… vs sweet corn which is I believe 8-10 weeks of growth. Or do all corn plants tassel/silk around the 2-2.5 month mark?
Is DTM of popcorn when it is “fully mature” but NOT sufficiently dry yet (so, do you add a couple of weeks after the official DTM of popcorn for drying time)? Or is DTM of popcorn when it is sufficiently dry on the stalk? (In comparison, for instance, for dry beans the DTM seem to be for when they are dry enough to harvest around 90 days.) And when does popcorn tassel/silk in comparison to sweet corn? (And as a side note, has anybody grown 3 types of corn in one season, 1 sweet and 2 types of popcorn?)
The reason is I’m planning on growing Japanese Hulless popcorn whose DTM online ranges from 85-110 days (usually stated as 85, earlier than other popcorns) and True Gold (su) sweet corn (70-80 DTM). They usually state to sow the popcorn first because it takes longer to germinate and can germinate in cooler soils. But the DTM of both varieties in this case seems to me like they may then overlap in tasseling/silking times if I plant the popcorn first, no?
Days to maturity is always to “market maturity” aka when you want to eat it. Don’t know if there’s a real relationship with tasseling, but my popcorn usually tassels well ahead of sweet corn when planted earliee as recommended.
I actually don’t worry too much about cross pollination, if that’s what you’re concerned about. While corn CAN pollinate from miles away, the pollination rate drops off dramatically even 10-15 ft away. You’ll get some cross pollination, but not enough to matter for crop or casual seed saving purposes. I’ve actually had pretty good luck selecting a strain of purple popcorn in a community garden setting.
Supposedly, popcorn does not cross-pollinate well with other classes of corn, but I can’t recall how trustworthy a source I read that from. I’d believe it, but don’t think I’d count on that alone. If it does pollinate with sweet corn, there’s a dead giveaway in the form of a shriveled kernel, like sweet corn.
Sweet corn days to maturity is how many days until it is in the milk stage and ready to eat. Popcorn days to maturity is idealized a bit but means standard number of days from planting until ears can be harvested. Popcorn is often slowed down by cool spring temps which can push maturity out. After harvest, popcorn should be shucked, then dried until moisture level produces best popping volume. As a generalization, popcorn tassels 2 or 3 weeks after most sweet corn if planted at the same time, however, this is not reliable to prevent crossing.
Now for the genetics. Many - but not all - varieties of popcorn have a gene that prevents pollination by most other varieties of corn. Only varieties with that gene can cross with popcorn containing the exclusion gene. But there is a problem with sweet corn which can easily be pollinated by popcorn pollen. I have grown popcorn beside sweet corn about 28 years ago and had a lot of sweet corn kernels that were not sweet. It is not a major problem unless you are growing for seed. Now the risky part. Some sweet corn contains the exclusion gene and therefore will cross direct with popcorn. If you grow a sweet corn with and popcorn with, you get massive crossing. Grow a sweet corn without and popcorn without and you get massive crossing. Only when one has the exclusion gene and the other does not is it possible to grow one that stays pure and the other gets massive crossing. So if you want to save seed, you will have to use another form of isolation to avoid crossing. You have two tools, isolation by distance, and isolation by time. Plant the popcorn 4 or 5 weeks before sweet corn and they will tassel such that crossing is minimal. Separate them by 100 feet distance and crossing will be minimal.
Read about “Rebellion” corn on Sandhill’s site for some gene info.