Could you advise us on what your 4'oclock is...use a latin name?
I am assuming mirablis jalapa when someone says 4'oclock, but your description of bushy vs vining confuses me and makes me assume the assumption is bad.

i have grown 4 oclocks ... mirabelis .... for 20 years... never trimmed one in my life ...

as noted.. a pic might get us an ID.. so we can be sure we are all talking about the same thing

ken

The vine versus bush concept had me puzzled too. The OP's member's page says they live in Greece, not Maryland as the post implies. I Google Don Diego and it seems to be a common name for Mirabilis jalapa in Spanish - Don Diego de Noche. (Whether it is similar in Greek or not I have no idea)I also found Google images of Ipomoea (Morning Glory) labelled as Don Diego de Dia.

I think that may be where the OP's confusion is coming from.

Whoops. I have no idea why I put Greece as my location when I made my account(it was some time ago and I never corrected it, guess I just rushed when I made it), sorry.

Yeah, dondiegos mix is just what it says on the seed packet, so I thought it was relevant. I think they are just mirablis jalapa.

When I said that they are bushy, I meant that they are not of a vine variety and have a stem unlike other morning glories I have seen. I wanted to trim it because it looked a little lanky, and is outgrowing some supports I have placed around it. It's also not making as many flowers as it used to.

I apologize if I didn't make it clear, I'm still a little new at this.
I'll follow up with some pictures soon.

In warmer climes (zone 7?) they form a tuber and do live over the winter. I found a garden web post from the Ozarks (using google) where the poster said that her four-o-clocks grow shoulder high.

As this has never happened to me, who live in colder climes, I have never had that problem. Mine make new plants from seed every spring and the old one is killed by winter cold. The new ones never exceed knee height.

On that basis, I would suggest you experiment with cutting your plant back to the ground (or some of it) and if that doesn't work, or you don't like that idea, allow some seedlings to come up and start over with newer, smaller plants and rip out and compost or give away the old tuber. Alternatively, I don't know if the tuber can be cut apart and propagated from small pieces -- that could also result in smaller plants -- temporarily. Stem cuttings of soft growth might also work, if you are attached to that particular clone.

Here is a link that might be useful: Ozark four-o-clocks

Gardener103 - now I understand where the confusion is coming from. I believe that the cone shaped flowers of Mirabilis jalapa have caused you to think they are a bush variety of Morning Glory. MG is usually used for species and cultivars of Ipomoea or, sometimes, Convolvulus.

Despite the superficial resemblance of the flowers the two are not related and advice on one is not relevant to the other.

I've never grown either but if you make sure you seek advice on Mirabilis jalapa and ignore anything about the Morning Glories you should stay on the right track.

In general, once a plant sets seed it's done what it's life purpose was. It can stop flowering and devote energy to maturing the seed. The best way to deal with that is either a light shear when most of the flowers are done, or better, individually remove the seed pods as soon as the flowers fall off.

Some plants flower again, 4 oclocks are likely to, if you leave them alone. The first flush of flowers are the most significant though.

If you cut them back severely, they'll go dormant, die, or just make new vegetative growth in the amount of time before frost. They don't like cool weather, and they don't probably have time to get new growth to the point of flowering much.

If you expect them to return next year, you need to give them time to just recharge their batteries and store food in the tubers. They are not perpetual flower machines, if you want those, plant impatiens or marigolds, or morning glories.

my 4oclocks... are a late summer bloomer ... and dont not stop blooming.. until the are frosted to the ground.. they do not winter over for me in MI ...

they are one of the exceptions to the 'stop flowering' after setting seed annuals ...

i try to keep a dozen or two of the hand grenade looking seeds for planting next spring ..

a good percentage of those that self so usually come back in my z5 ... IF ... there is enough snow cover to keep the cardinals out of the bed ... and if i have a z5 winter ...

we had a z4 winter last year.. and i was surprised... that under 3 feet of snow.. the entire crop of self sown seed.. failed this year ... and then with a spring that was 4 to 6 weeks late ... the very few i have are barely 8 inches tall ... i am not sure if they will get to bloom ...

ken

I wished mine looked like that! California, drought area. Don't know whether to cut these leggy stems or not.

My 4 oclocks are lush and green in pot and just went through 100 degree .....weather looked bad brought inside gets late Sun 4-6 hrs in window several blooms no flowers could I have shocked them bringing

My 4 oclocks easily get 10 ft tall in some beds. I have dug tubers larger than my head. Needless to say I have vary mature plants. Here in Texas they tend to get leggy and droop in the heat. They take off again in the fall. but I wondered about trimming them back if that would hurt the plant or their fall flooms

UPDATE: I have trimmed my 4 oclocks.. and they have con't to bloom well for me.