Please note: I'm am no corn expert. Ignore my response as you see fit.

size size.... is it as tall as an elephants eye? I think that's how they measure it officially. Are you getting full sun in the greenhouse? Is it just growing taller reaching for the sun ?

Did you plant a block of them together for fertilization? Corn is wind pollinated, so I would think it could be an issue in a greenhouse unless you get all mavguyver on the corn when no one is watching

Never, not sure how high an elephants eye is but this afternoon one stalk reached 12 feet!!!!! It's just barely touching the top of the green house! I do get full sun until the mid afternoon but because of the translucent nature of the polyethylene, nothing gets direct sunlight. The corn is planted in blocks and I have to fairly large swamp coolers blowing from the same end of the greenhouse towards the corn. I suspect they will be enough but just in case we'll also be doing the pollination ourselves.

TOXC - Just today I noticed that most of the stalks are beginning to get thicker right at 2 of the lower leaves and a number of them have already started to silk. I'm hoping I was concerned over nothing!

Now my problem is that I can't keep the watermelon and giant pumpkin vines from climbing up the corn! I'm having to cut the vines down on a daily basis. I'm beginning to think my greenhouse is haunted by the ghost of Audrey II in the Little Shop of Horrors!

you know, out of curiosity several years ago I planted sweet corn in a semi-shady bed. It grew to 12 ft, and even made ears, though not great production. The beds had been heavily composted the year prior, and I fed it normal amounts of urea (normal compared to other veggies). Due to the semi-shade light was coming from various directions, so that may be the answer to something I never quite understood.

Corn with to much nitrogen in the soil can result in no fruit. Did you do a soil test before fertilizing? You also need to remember corn needs air flow for pollination.

Yes after the tassels form but it really needs wind to spread the pollen.

Did you know each one of those hairs leads to a kernel that needs pollination? Or you end up with those missing kernels.

Over the past 3 days the ears have really started showing up. Some stalks have 3 ears!! I didn't think that was possible but I guess with the stalks being so tall there is enough room. John D., I did not do a soils test but obtained the test results from the company I bought most of the soil from. It was somewhat deficient in all areas - NPK - but not too bad. I have a fertigation system through which I added enough to cover the deficiencies - at least I think I did. I also have been amending much of the soil with compost I've made "from scratch."

Gumby, I'm hoping that the breeze from the two swamp coolers I have blowing from the opposite end from the corn will be enough to take care of the pollination but just in case I'm also self pollinating by shaking the top of the corn stalk so the pollen falls down on the tassels you mentioned. I was surprised to learn that about each tassell being attached to an individual kernel just a few weeks ago. Very interesting.

Most sweet corn will start with 2 'ears', but only finish 1...maybe 2 if vigorous enough.

There are "ancient" corn that can produce 3+ ears. I have read about a Idaho farmer a variety of popcorn that puts out multiple fruit.