Maintenance of Grasses

By Admin on 15-09-2014

While the maintenance requirements of native grasses and strappy leafed plants are minimal, they are like all landscape plants and some management is necessary to keep them looking at their best. Trimming is the primary maintenance requirement of these plants, however, fertilising, mulching and some watering is also beneficial.

The plant profiles on the Gardeners Planthub website http://www.theplanthub.com.au detail the maintenance requirements of each plant in our selection. Maintenance descriptions have been based on 3 levels of trimming frequency – Level 1, 2 and 3.

Trimming

Too often the assumption is made that native grasses and strappy leafed plants need zero maintenance. In the natural environment these plants have both adapted to, and even depend upon grazing and fire. Such processes can be easily mimicked in the landscape by regular trimming. Well timed trimming removes last season’s foliage, including spent seed heads; encourages fresh regrowth during the plants ‘display’ season; promotes flowering and in the case of some Dianellas, makes room for new foliage from the basal clump.

So, how often is trimming required?

Maintenance Level 1 plants require trimming on an annual basis and include all the grasses in our selection. ‘Warm Season Grasses’ (WSG), such as Themeda and Pennisetum are best trimmed in early spring. This removes the growth of the last season and encourages fresh new growth in the warm months when these plants look their best. On the other hand ‘Cool Season Grasses’ (CSG) in our selection include Poa 'Kingsdale' and "Eskdale'. Their best foliage displays occurring in autumn and winter and therefore best trimmed annually in March and April.

Maintenance Level 2 and 3 plants include all of our ‘Strappy Leafed Plants’ (SLP). Maintenance Level 2 plants perform best if they are trimmed every 2 to 3 years. This includes Dianella 'Lucia', Dianella (common form) and some of our sedge plants.

Maintenance Level 3 plants respond well to trimming every 3 to 5 years. This includes Dianella 'Little Jess' and most of our Lomandra cultivars.

Timing of trimming for Maintenance Level 2 and 3 plants from Gardeners Planthub selection is less imperative than Maintenance Level 1 plants. The decision to trim should be based on plant appearance, soil moisture and seasonal conditions. For example, it would be beneficial to prune a mature Lomandra showing signs of heat damage following the hot dry months, particularly if rain has occurred or a watering regime was introduced. In some cases where foliage remains fresh and healthy and the plant continues to flower, trimming may be unnecessary.

How much to trim

For both all grasses and strappy leaf plants a good rule of thumb is to remove 1/3 to 2/3’s of the leaf height. So if the plant is 600mm high you would cut it back by 200 to 400mm, leaving a good healthy base from where the new growth will emerge.

The pruning of SLPs differs according to their habit. If the plants are rhizomatous cut the foliage back to between 100 and 200mm from the ground as new growth will spring from the rhizome. Rhizomatous SLP’s in our selection include Dianella 'Little Jess' and 'Lucia'. If the SLP has a clumping habit, such as Lomandra, pruning is the same as for our grass range. Cut back the foliage by 1/3 to 2/3’s the height of the plant.

Yes, trimming in this manner can seem very dramatic. Particularly when trimming our grasses and SLPs for the first time. Be assured that provided the specifications in the plant profiles on our website are followed, you can be confident of a great result. A few things to consider and avoid include:

  • * do not trim grasses too low as this may expose the crown to damage. 100mm from the ground should always be the minimum. As with a lawn, if you scalp the grass it will take longer to recover;
  • * avoid pruning in hot weather or if the plant is under stress. This applies to most landscape plants;
  • * in frost prone areas, take care to protect basal clumps by retaining last years’ growth until the frost period has passed. This is particularly so for WSGs as these are pruned in early Spring when frost may still be about;
  • * when designing a landscape, avoid using a high proportion of grasses and SLP’s that will require pruning at the same time. An unfortunate result of making this mistake will be a periodically denuded environment;
  • * avoid carting large volumes of trimmings. These can be used as mulch on site, preferably under existing mulch or “top-up” mulch, or disposed of in compost heaps. Trimmings add carbon to the compost environment which is beneficial to most household compost heaps where nitrogen is commonly too high for efficient composting.

Why, when and how to fertilise

Generally fertilising should be undertaken after trimming with a slow release fertiliser to encourage new growth. Native fertilisers are suitable for grasses and SLPs, however, their use is not essential. Unlike many native plants, grasses and SLPs in our selection respond well to nitrogen, therefore the use of general garden fertilisers is suitable. Fertilisers with very high nitrogen levels, such as fresh manures are best avoided.

Mulching

Mulching retains soil moisture, inhibits the growth of weeds and reduces soil temperatures in hot weather and insulates it in winter. Such benefits are particularly important in harsh environments.  Choice of mulch can be largely based on personal preference. One exception to this is in areas experiencing high humidity and rainfall in late summer where an open mulch is preferable to avoid issues with a fungal attack of plants. Gravel or course woodchip are examples of open mulches. As with the application of mulch to any garden plant, to avoid collar burn, mulch should not be piled up around the base of the grasses and SLP’s.

Watering

Even though our grass range is tough. all plants require some watering in dry times to look and grow at their best. While their requirements are minimal we recommend watering upon planting and during establishment, this will improve survival rates. Watering before mulching is always good practice. Also watering during particularly hot and dry periods can be necessary to avoid replanting, preferably before plants show signs of severe stress.

In short Gardeners Planthub range of grasses have low maintenance requirements however are not maintenance free. Follow the tips above and the specifications given on our website and you will enjoy a fantastic result.

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