Unless it’s an annual, pruning is eventually required for all landscape plants. Many new landscape plants have been bred for less pruning, but with modern equipment should we really be pruning less or more? What are the best techniques and equipment for shrubs, grasses and groundcovers? Pruning trees is far more technical, so that’s a story for another day.
Working our way up from ground covers to shrubs, our modern ground cover plants are denser than landscape ground covers of decades past. Breeders over the last 2 decades have introduced many new ground covers with shorter internodes. Grevillea groundcovers have become more prostrate and, recently, prostrate Westringia ground covers have been introduced.
More prostrate will mean less vertical pruning, but keep an eye on the spread of these modern ground covers. Keeping them regularly in check by edging their lateral growth is essential, but with the increased proficiency and ease-of-use of modern pruning equipment, why stop there? More frequent top pruning will result in neater plants.
Some groundcovers benefit from running a mower or brush cutter over them once a year. In the USA in Texas, you can drive through suburbs in winter and see most of the liriope, mondo, and vine type plants like Asian Jasmine cut back with a lawn mower or brush cutter. Soon after in mid spring drive by and you will see vibrant clean foliage ground covers throughout Texas. Maybe it’s time for Australian gardeners and maintenance contractors to contemplate similar methods.
Vines grown as groundcovers, if left unpruned for several years, generally become unappealing. They may harbor insects and rodents, experience foliage and branch dieback, and lose their landscape usefulness. Cut out the top one-third of overgrown or stretched out stems. Prune old mature stems that are decreasing in vigour by a third or even more. The cooler months are the ideal time to do this both in Australia and the warmer parts of the USA. Ensure the mower or brush cutter blades are sharp, otherwise the aftermath can be worse than not pruning at all.
On the other hand, many modern ground cover plants may not require regular pruning to survive or to look reasonable, but to look spectacular or to achieve a more formal look, light pruning 4 to 6 times per year can produce amazing results. A couple of examples explain best. Grevillea juniperina or the popular Westringia groundcover ‘Mundi’ can be pruned once per year for a native finish, or pruned 3 to 6 times per year for a tidy modern clean finish. In summer if you prune every month and a half, the finish is amazing, akin to a manicured lawn. Treat these Australia natives like exotics, and you get a more formal finish. Never prune back hard if you are pruning this often as this can hurt the plant, but consistent light tip pruning can be done all year in most parts of Australia. These days an argument could be made that regular light pruning with quick efficient machinery is just like regularly mowing the lawn. Twenty years ago this would have been crazy, but pruning equipment has come a long way.
Strap-leaf plants and ornamental grasses
These are a major component of our modern landscape. Cutting these back is vastly different. Firstly you should use very sharp equipment such as knives, hand shears, or brush cutters with blades rather than cord. Hedging machines usually tear these plants, and the leaves quickly blunt the blades. Brush cutters also tear unless you keep the blade very sharp. If you are a commercial landscape manager, it pays to have a couple of blades for a day’s work, sharpening them before use again.
For Lomandra, Dianella, and most strappy leaf and grass plants in large scale plantings it is best to cut the plant back to no lower than 15 cm. This ensures the plant will survive. Avoid pruning in a drought, or in the middle of summer. In a home garden you can cut to the ground if you use a two-step method, which will be explained shortly, but my preference in a home garden is to cut the plants back to about 20 to 30cm in a ball shape. It looks great.
Fine leaf Lomandra longifolia types, such as ‘Tanika’ and ‘Katrinus Deluxe’ look spectacular when pruned into ball shapes.
- • Liriope can always be cut to the ground, preferably in winter.
- • Poa can be cut back very short in late winter, early spring, and autumn, never summer.
- • Pennisetum is best cut back in late winter, early spring, and can be cut back hard.
In a garden situation, it may be more desirable to cut Dianella and Lomandra close to the ground. Usually, plants will survive that, but occasionally some drop out. To avoid dead plants, you can prune in a two-step process. Cut all but about 10% of the leaves back just above the ground, leaving a few on one side longer. In a few weeks after the rest of the plant has started to reshoot, come back and trim the last few leaves off to the ground. Many strap-leaf plants can cope with pruning every 5 to 8 years, but they look a lot better if pruned every 2 to 4 years.
Modern long-reach hedge trimmers are the perfect tool for ground cover or shrub pruning. You do not need to bend, or move as often, making pruning not only more pleasant but more efficient. They have the potential to enhance safety, by moving the trimmer further away from the operator.
Pruning shrubs can easily be achieved with a light weight hedge trimmer, and some operators prefer these, but for taller operators, the long reach types are more suitable even for both shrubs and groundcovers. There are so many great brands of hedge trimmers to choose from these days. They are far more efficient making pruning super-fast which allows for more frequent hedging, and for people using contractors far more cost effective. Some systems use a multi-tool system making them super versatile.
Whatever machine you use, or even if you use hand held shears, pruning frequency on shrubs depends on the desired look. If you what a formal hedge, then more frequent light pruning will result in a more manicured look. If you want a native or natural look, strategic pruning once a year is all that is needed. Leaving some shrubs for more than a year unpruned may result in an untidy plant, which has grown into an undesirable shape that is hard to fix without drastic pruning. Sometimes it’s time for a massive cut back. One consequence is that the shrub may be lost, but if it survives the plant will eventually look so much better. Usually it is worth the risk. Plants are not that expensive after all.
You now have the machines to prune efficiently, and with more frequent use you may just improve the quality of your landscape. Happy pruning!