Root-prune large gardenia before moving it

By Audrey Post
MS. GROW-IT-ALL®

Q: We have a large gardenia bush in our yard that has overgrown its space and needs to be removed. It’s probably 6 feet tall by 4 feet wide. Is it too large to move to another spot and if not, what’s the best way to do it? It’s about six years old.

A: They look so cute when we bring them home in their little 1-gallon pots that it’s sometimes hard to visualize how large they’ll eventually become. And when they do outgrow their spaces, we like to think it’s because of our skill at site selection – “It was just so happy there!” -- and the excellent care we gave them.

But regardless of the reason, whether planted in too small a space, changes in available light because of new construction or tree removal, or supercharged genetics, small trees and large shrubs sometimes need to be moved. Root-pruning is the best way to prepare your gardenia bush for the big move.

The theory behind root-pruning is that by severing the long roots that extend beyond the drip line, you force the shrub to grow new feeder roots closer to the trunk. These feeder roots will be part of the root ball when you dig the gardenia and move it to its new location in several months, so the shock to the gardenia’s system will be lessened.

Take a flat spade or shovel and thrust it into the soil about 15 inches out from the trunk of your shrub. Make sure you push the shovel down about a foot so you cut the roots running laterally. Now make another cut right next to the first one, and another one next to that one, until you have a circle extending around the shrub. You’ll need a sharp spade to cut the roots. If you encounter a particularly thick one, you can use loppers to snip it.

Ideally, you wait about six months after you root-prune to move the shrub, but three months is the minimum. If you root-prune your shrub this weekend, it should be ready to move by February or March. April is probably the latest you want to move it because May is when the summer heat really starts cranking up.

The heat is the same reason you want to root-prune in fall and transplant in spring in the Deep South. Growth is slowed over the winter, so the severed roots won’t hurt the plant the way they would in summer, when it’s in growth mode and dealing with heat stress. In areas farther north with less intense summer heat, the reverse would be true: Let the shrub grow new feeder roots over the summer so it can survive a cold winter.

You’ll probably need to prune the gardenia back a bit when you move it, but don’t whack it all the way back. The old argument for drastic pruning when you move a shrub was that the root-ball couldn’t support the entire plant, because it lost the feeder roots when you dug it. By root-pruning, you lost those feeder roots several months earlier and the root-ball that you dig is actually what was supporting the entire bush.

Besides, you need those leaves for photosynthesis to feed the plant and help it get re-established.