I have two gardenia bushes that were probably planted when the house was built, so they may be 14 years or so. They were both huge. One blew over in a storm; I replanted it, and when it was still not doing well, I pruned it back, hard. It has come back but is much smaller than it's huge mate, and so they both look awful. I'm thinking of trying to prune the huge one way back but wonder if it's worth it, and would it even survive a hard pruning. At what point do you decide to just dig up the plants and get new ones? I HAVE to have gardenias, I love them!
Ofcourse, the more severely you prune your gardenia, the longer it's going to take to grow back. I'm not sure if late summer is the ideal time for hard pruning. Is it possible your gardenia was under ground vole attack, which caused it to blow over in a storm? It seems unlikely that a healthy well rooted 14 yr old gardenia would become uprooted and blow over in a storm. I've lost several gardenias to voles. A couple years ago, I saved 2 by digging them up and replanting in large plastic containers. Once the root system has been disturbed and they are hard pruned, it takes a couple years for them to begin to rebound.
If you want symmetry by next summer, you might want to consider digging them both up in late winter (mid Feb), moving them to another part of your yard, and planting 2 new gardenias in their place. I'm growing 4 different varieties of gardenia, but the old fashioned is still my favorite. If you go this route, you'll need to cut back your healthy rooted gardenia so it can survive the move.
In my experience, cutting back really mature shrubs expecting them to grow back nice & full is fruitless and you end up with pathetic looking spindly and sparse plants. If you must do that then also cut the roots all the way around within a foot of the main trunk .. that will sometimes give the mature plant extra vigor and grow in denser since it will start growing new roots. Personally I'd just get new.
Thank you ladies, I think I will do both: try transplanting the trimmed down old ones somewhere else in the yard and see how they do, and for the sake of eye appeal, plant two new ones in the old spot.