A couple of people have asked me recently why their beautifully big, green, and healthy tomato plants have no flowers and fruits. It is perfectly understandable that they would be confused, because anyone would expect that a healthy plant would be a productive plant. Weirdly enough, it is possible for a plant to be too “green.”
Usually, a plant (the kind from which we expect fruit) that is all lush green leaves and stems with no flowers and fruits is getting too much nitrogen.
I heard the N-P-K combination in commercial fertilizers explained once as Up-Down-All Around. The nitrogen (N) is for top growth (Up), the phosphorus (P) is for root growth (Down), and the potassium (K) is for “all around” growth. That is an over-simplification of what the nutrients do, but it gets the basic point across and is easy to remember. And what it helps us know is that, somehow, those lush tomato plants have had access to too much nitrogen.
There is no easy way to get those plants to make tomatoes that I am aware of. Eventually, given enough time, the nitrogen will become less abundant in the soil and the plants will flower. However, it could take many weeks of waiting, depending on how much fertilizer was accidentally used on the plants.
My step-dad Grandpa Bill, though, has said that such plants can be stressed to get them to flower. Grandpa Bill is in his 80s and has been gardening in Oklahoma for his entire life, so he knows quite a bit about gardening. He says that one way to stress those plants is to just “whump ’em.” A hail storm can do this for you, and if you are in Oklahoma, hail storms are common enough that a gardener with too-lush tomato plants can just wait for one.
When no hail has been forecast, he has known farmers and gardeners to actually whack the plants with sticks, to get them bruised enough that they have to use up a bunch of nitrogen in tissue repair. In a week or two, the plants start to flower.
I have never had the problem of too-lush tomato plants, so I have not yet had the experience of beating up my tomato plants, but I would really like to see this personally.
Another, less weird way to stress the plants might be to do some pruning. The plants would then use up nitrogen in the new growth that they would put out to replace what was lost.
It’s an interesting problem.