Shrubs can take many years to get established but once they get out of control you don't have to resort to chainsaws and pickaxes to rip them out. Sometimes it is better to keep the established plants and give them a makeover. If you can do it to the house – why not the plants as well?
BEFORE YOU START
Your makeover will challenge the plant so before you start give is a good deep watering (aereate the soil under its canopy with a fork to ensure the water gets in to the root-zone). Then sprinkle some “Blood and Bone” over the soil and lightly rake it in and give it one more good watering. Its like giving your plant a packed lunch before going on a long journey.
a. Shrubs that grow from a framework of branches. (like Murraya, Camellia, Callistemon or Grevillea)
N.B. Illustrated is a Grevillea Robyn Gordon - always lush and lovely when young but invariably become woody and unattractive in time.
To reduce their overall size cut the tallest branches back by half and give it a good tip prune all over to give it some shape. This is always best done in Autumn if you cut back hard but can also be done anytime of the year if you take a bit less off.
N.B. if its in flower then wait until its finished.
Now wait until you see some new growth established on the branches you cut back hard. Once that has established you can then cut back hard on some of the other branches. It’s a matter of staggering the impact of your cutting to give the plant the best chance to sprout new growth and gain some vigour before cutting more back.
Once you've achieved a smaller shrub with vigorous young growth, thin out any weak, badly placed, or crowding shoots.
To salvage these kind of shrubs usually takes about two years to get them to their new best – which is a lot less than planting a new one which may take five years or more to get to the same size and condition.
b. Shrubs that grow from the base. Many thicket type shrubs that grow directly from the base, sending up stems (canes) from the roots, can take much more severe pruning. They include Abelia, Forsythia, Tibouchina and Oleander.
(Tibouchina Althonville illustrated here)
With these you can go crazy and hack them right back to the ground (well leave about 30cms above the ground) but make sure you do it in winter before new spring growth begins.
Also be sure you cut cleanly with a sharp saw or pair of loppers. If you leave ragged cuts then borers and other insects can get in and damage the wood.
These plants actually benefit from cutting back this hard once every three to four years – it stimulates new growth and the plant will remain vigorous and lively for many years – and because they are always fast growers you can expect the hole to be filled within one year.
N.B. If you can’t wait until winter then just prune back by at least one third or even a half right away and then do a big cutback the next winter. Whatever you do, wait until it has finished flowering - the Tibouchina will be well into winter by then.
Cane-like plants like Abelia need fresh growth to stay healthy so regular pruning is always good to keep them bushy. They will also reward you by growing back very quickly.
TRANSFORMING SMALL SHRUB TO TREE.
If a shrub has one to more largely upright main stems and a framework of branches, you can convert it to a small tree by simply removing the lower branches.
If just one main stem is in good shape or well placed, cut the rest to the ground; the remaining main stem will become the trunk of the "tree."
In the case of this Tibouchina on a golf course, three stems provide the central trunk giving it a distinct tree-like shape.
Remove side stems on the trunk up to the point where you want branching to begin.
If the shrub has several good stems, you can keep them and just take out the weaker ones .
Then remove side stems up to the point where you want branching to begin; then thin out those that remain to form an uncluttered crown for your new tree. This approach can be done in one go (rather than staggered over a period of time) as the plant maintains a canopy of leaves to keep the photo-synthesis going (that’s what keeps it alive).
As with all pruning ensure you use a sharp blade on your saw or loppers and try not to do it when the plant is in flower.
So if your first reaction to an overgrown garden or a weak and tired looking shrub is to “Hack it Down” then think again. Sometimes an established plant will reward you quicker than starting from scratch.