I see hibiscus hedges all over the tampa bay area. Quite a sight too. I haven't done this but I have seen "triple" hibiscus that are twisted together to give a "hibiscus tree" with three different blooms, so I don't think it would be a problem.

The process is called "Bap" for Build a Plant, where you put several plants in the same hole. I've done it several times with Hibiscus, however I use 3 different color flowers. One hole, three plants, stuff them in and move the branches around so that they intermingle.

To follow up what fawnridge said, the most attractive groups of hibiscus that I have seen are those with three different colors close to each other. Clearly, though, the closer you plant them the quicker they will grow together and compete for sun and nutrients.

Thanks All, I will move ahead. I have three in one gal pots that are very leggy so when I replant they will be trimmed back and the cuttings rooted for more plants.

I was thinking about 1 foot to 18 inches apart.

I'd like to see that intermingle effect, but I am more of a stand alone gal myself.

I have trimmed one of my hibiscus as a standard and planted Duranta and African Iris around it. I think your hibiscus hedge will come out vey nicely.

Seems like some varieties are more hardier than others. The red ones were beautiful but would grow almost up to the roof line if I didn't cut them back. My pink ones now are easier to keep under control and the cooler temps don't seem to bother them. Still blooming Jan 1, 2015.

I have this 10 foot mound/island in my yard. A coconut palm was in the center, but got hit by lightning and died. SO I decided to plant hibiscus.

I put 3 one gallon plants at the top of this mound (about 2 foot elevation) and they have done what I wanted. They have merged together into one nice multicolored bush. It's 2 yellow and one peach. Now I wish I had planted a red instead of one yellow, but it does look nice - if I do say so myself!