Has your weather been cool and maybe rainy, more so than usual?

There are many varieties of Japanese Morning glory vines. Some grow more quickly than others. Some are very short and are better grown in pots.

Climate, weather, i.e rain, cool temps, lack of sun can all contribute to how the vines grow and how quickly they do grow.

Also remember that if the vines are growing slowly do to various unusual weather conditions, the purpose of the vine is to bloom, produce seed pods and then seeds to reproduce the next year.
That is mother nature's plan and if there is a monkey wrench thrown into the mix, i.e. weather, then the vines will flower much earlier than one would expect and on very short vines.

Also, morning glory vines will be happy with some fertilizer as well. I usually use miracle grow to fertilize them. When I plant my seedlings they get a good size scoop of miracle grow potting mix into the hole and a few weeks later I will give them a boost with some miracle grow fertilizer.

I've had various growth patterns with many different Japanese morning glory vines, depending on the weather.

Unless they are the low growing type that are more conducive to growing in pots, they will fill out and vine tall for you. Just may be a matter of time and weather.

Fran

They need sun, lots of sun, and if you have gotten "quite a bit of rain lately" then you are missing enough sun.

My MG vines are still very tiny. Usually they are a good 5-8 inches tall by now and well into vining up my chain link fence.

But, only about 3 days this June have had any sun. All we have had is rain, rain and more rain.

Last year, they where growing quite well in June, then we had almost 31 days of constant rain and deluges of rain in July. Everything was stunted in growth, especially the morning glory vines.

Once the rain stopped and the sun came out in August, of course minus any rain at all for the entire month, the vines took off and grew.

You original post stated that this has happened to you before, do you have the vines growing in full sun? Or mostly full sun? If not, that could be a problem.

Have you given them any fertilizer?

I have had morning glory vines bloom at 3 inches too, even had one bloom in a 12oz styrofoam cup one year. Forgot all about the cup with the seed in it as it had not germinated outside. Didn't toss the soil either, just had it in a corner.
One day I noticed this strange flower coming out of the cup that was at the edge of the fence. Low and behold, the seed had germinated, grown a 3-4 inch vine and was blooming with one flower and about 6 more buds on it. It got in the ground real quick.

Sounds like mother nature is in desperation mode where you live. Got to get those flowers blooming, got to turn them into pods, got to get those pods to make seeds, got to get those seeds on the ground for next year, no matter what is going on.

Try and be patient with them, give them a boost of some fertilizer, I like miracle grow personally, and hope for some sun. If not full or mostly full sun, maybe you could move them to get more sun.

Mt fuji and chocolate silk are good vining MG, blue picotee is a small flower that is good for pots.

Fran

I would recommend using a nitrogen fertilizer (that is low in phosphorus) on your plants although don't use too much.

The reason I'm recommending the nitrogen for you is that high nitrogen will often cause the vines to elongate quicker and delay flowering...
so , the application of nitrogen in your situation may produce longer vines that will not flower so soon...
since the plants will often stop growing (or grow much slower) once they flower...

You'll probably need to experiment to find the right NPK ratio and application regimen for your young plants...correct dosage at various stages of growth is important...you don't want to burn the young plants by giving too much , yet you would still want to provide enough to stimulate growth with delayed flowering...

Hope that helps...

TTY,...

Ron

The gibberelic acid will cause vine elongation and delay flowering...