Question:  We have had four o'clocks for a few years. This year they have good stems but the leaves are completely stripped away. And no flowers. Seems to be progressive moving right on down the row. What could be causing this?
Answer:  Four O'Clocks are one of the most disease/pest free plants around, and I had to do some serious looking to even come up with any kind of answer at all for this one.  The only time I have ever seen Four O'Clocks completely defoliated is after the first few light frosts, but as I write this it's mid July, so that certainly can't be it.  I thought through various diseases such as bacterial and fungal diseases, and none of them fit at all, because if you had something serious like that the plant would be noticeably sick as a whole, but you say the stems are healthy.  Deer and rabbits don't like Four O'Clocks either so that's not it.  Since Four O'Clocks are a part of the Nyctaginaceae family of plants, with the most well-known relative being Bougainvillea, I looked around for something that might completely defoliate a Bougainvillea plant, and lo and behold I may have your answer.  My best guess as to what is going on with  your Four O'Clocks is that they are getting eaten by Bougainvillea Looper, a brown or green moth caterpillar that is about 1 inch long and moves by contracting and expanding (it's sometimes called an inchworm because of this). I am aware that you didn't say anything about the leaves being chewed, and this concerns me, but otherwise this fits your symptoms pretty well.  This caterpillar is a voracious eater and can apparently easily defoliate an entire plant in short order.  This might explain why the problem seems progressive - they are just inching down the line.  Bougainvillea Loopers feed at night and disguise themselves well during the day, so at this point to confirm or disprove, you will have to go out there and look really closely both at night with a flashlight and by day, where they will blend in to the existing stems and foliage so well they are almost undetectable unless you are specifically looking for them.  If you find that indeed this is your problem, go to the garden shop and get some Dipel (also called BT), which is a natural pesticide that will eliminate the problem without destroying every other beneficial insect in the garden.  Good Luck!

Question:  My Four O'Clocks are about 4' tall and haven't bloomed.  They have never gotten this tall and have always bloomed. I love them and all my others aren't nearly that tall and are loaded with flowers.  What has happened to this one?  We are in North Florida.  What do we need to do?
Answer:  There are only a few things that can go wrong enough with Four O'Clocks that would cause complete lack of flowers, and number one in my experience is too much shade.  Four O'Clocks will tolerate some shade, especially in hot areas like North Florida, but it's a fine line, and if you err on the side of too much shade, the result is no flowers every time.  Are there any structures, shrubs, trees, etc. around this particular plant that might be reducing its sunlight?  After receiving this question, I went out in my own yard and looked around (I have a lot of Four O'Clocks), and sure enough, there is one on the north side of my house between the house and my above-ground pond that only has a few blooms on the very top.  If yours is in a north-facing position and is against or beside any kind of structure, this is very likely your problem and this is my first and best guess.  Other less likely considerations would be too much sun, since you are in such a hot climate (which I doubt since you say the plant looks healthy), or that it's just a bit too early in your long growing season for blooms on this particular plant.  In my zone 7 Southeastern garden, the Four O'Clocks really are just now blooming full force as I write this in late August, and that particular plant might just be on a slightly slower internal clock than the rest for whatever reason.  I would give it another couple of weeks before giving up if none of the above applies.  If at the end of the season, the plant has never put out blooms, my best advice is put something else there next year that will be happier in that position.