Mixed Group Plantings: Queensland Focus!
By Todd Layt
There has been a trend recently to use more plants in smaller group plantings rather than in large mass scale plantings. If the right plants are used this can work well, but if weaker plants are used, then the concept is only as good as the weakest plant. So when designing mixed group plantings what do you need to do to make the project work long term?
Firstly, design with a decade of performance in mind as a minimum. Make sure the right soil is being used for the plants chosen. If you want more diversity, use organics in the soil to promote better plant growth. Remember, someone will need to maintain the landscape, so choose plants and mulch that will reduce future maintenance inputs. Too much diversity impacts greatly on the cost of maintenance.
Pruning or weed control becomes very costly with too much diversity – getting the balance right with enough range to be interesting, but not so much that the cost of maintenance sky rockets is a juggling act. The best ways to lower maintenance costs include: opting for large scale mass planting with plants that perform for at least a decade that need less pruning, using plants and mulch that help reduce weed pressures and equally as important is being very clever with plant selection for smaller group plantings.
The first and probably most important aspect is to get the soil preparation right; a good soil will help all plants perform far better, but it is not always that simple. Budget constraints often require the use of site soil. In this case, it comes down to plant selection, making sure you only use plants that can cope with the poor soils. Drainage is another important aspect; if the planting is on the lower side of a path, wet conditions will make that side damp for longer periods, so it is necessary to use plants that can cope with wet feet.
If the site is non-irrigated, which is often the case, the plants also need to cope with drought. Mulch selection is one of the most important decisions for the project. On a commercial landscape, the key role of mulch is to reduce weeds and its secondary role is to help add organics to the soil. Only chunky mulch with close to zero fines achieves the first goal. Mulch with small pieces or lots of fines actually acts as a potting mix and aids the germination of weed seeds.
Avoid tub ground site mulch with fines, as this not only helps weed seeds germinate, it also is often full of disease and can kill most of the plants in a landscape. If you are forced to use this, make sure the plants can cope really well with Phytophthora and other diseases. Ozbreed has a number of plants that cope with this type of mulch, so if you must use it call Ozbreed and a list of those plants can be provided.
Plant selection is the other really important aspect. Smaller group plantings are only as good as the weakest plant and the maintenance level is often set by the plants that need the most upkeep, so choose plants that need less maintenance. There are enough good plants available for your region to choose long lasting, low maintenance options and still have good diversity in the project.
Ten different plants installed in smaller groups of say 3 to 10 square metres per variety will provide a diverse landscape. Below is a list of the best 10 plants for your region that will not only provide diversity, but also great companion planting, low maintenance and a long lasting landscape.
Top 10 Native Plants for QLD Group Plantings
^ Plants are described from 1-10 from left to right
1) Shara™ Lomandra – The only compact, fine leaf Lomandra that performs in the humidity of Queensland, in drought or periodic wet feet, and is highly Phytophthora resistant. Copes with site sourced mulch.
2) Green John™ Callistemon – Tough as nails, Myrtle Rust resistant and smaller than ‘Little John’. Crisp, clean and green foliage that contrasts nicely with the red flowers in spring and autumn. Copes with site sourced mulch.
3) Grey Box™ Westringia – Small, compact Westringia that is longer lived and handles drought well, yet copes very well with wet feet and cold. Copes with site sourced mulch.
5) Little Jess™ Dianella – Needs better soil than the rest of the plants, but provided the soil is good and organics are used, Little Jess™ Dianella spreads and fills gaps, is low growing and looks great. Avoid for poor site soil situations, but if the soil is improved it will be one of the best plants in the project.
7) Nafray® Pennisetum – One of the best performers in Queensland over the last decade. Copes well with wet feet and dry conditions. It will need trimming to look its best yearly, preferably in late autumn or late winter. Copes with site sourced mulch.
8) Mundi™ Westringia – This ground cover Westringia has performed well in Queensland in the dry and in periodic wet feet areas. Copes with site sourced mulch.
9) Macarthur™ Callistemon – Ideal if you want a plant that is a little taller, but not too tall. Copes well with Queensland’s humidity and is highly Myrtle Rust resistant. Copes with site sourced mulch.
10) Tropic Cascade™ Lomandra – Has done very well in Queensland and provides a lower growing Lomandra hystrix that has amazing weeping foliage.
Top 5 Exotics for QLD Group Plantings
^ Plants are described from 1-5 from left to right
1) Just Right® Liriope – The only Liriope that does not burn in full sun. It is smaller than ‘Evergreen Giant’ and much tougher. This has been a real star in Queensland. Copes with site sourced mulch.
2) Obsession™ Nandina – The problem with Nandina in Queensland is the mild winters, and the fact that normal Nandina plants do not get really red. Obessesion™ Nandina does not need cold to go red. It is very red in spring, summer and autumn, as its new growth is always red.
3) Blush™ Nandina – More of a traditional Nandina look, but with red new growth in spring, summer and autumn.
4) Cosmic White™ Rhaphiolepis – An unbelievably tough plant. Dark green foliage and large white flowers twice per year, and best of all it rarely if ever procures a berry, so it will not become weedy. Copes with site sourced mulch.
5) Little Ruby™ Alternanthera – It will need some irrigation, so only use it on irrigated sites. It is more cold tolerant than the common form and it needs far less pruning as it is a low growing ground cover. The deep purple foliage will make any project look spectacular.
Best 5 Shade Plants for QLD Group Plantings
^ Plants are described from 1-5 from left to right
1) Little Phil™ Philodendron – This compact Philodendron is more shade tolerant than other types and really looks great in shade gardens with irrigation.
2) Katie Belles™ Lomandra – This plant copes with heavy shade, and even copes with wet heavy shade. Copes with site sourced mulch.
3) Tropic Cascade™ Lomandra – Its weeping foliage looks great in a shade garden.
4) Just Right® Liriope – One of the best shade plants for Queensland. Copes with site sourced mulch.
5) Silverlawn™ Liriope – If you want a little colour contrast in a shade garden, Silverlawn™ Liriope will provide that in spades. Note: Previously known as Silverstar™.
Remember, we are dealing with live plants and sometimes things go wrong in life, so have a follow up maintenance plan and at least one replanting phase if possible after one year to replace any dead plants. Landscape Architects and Designers often face a grim reality that the project did not quite turn out as planned after all the construction has been completed. Some areas may be wetter than planned, the mulch not as good, the soil preparation was not as planned, or weed invasion was worse than envisaged.
One or two of the plants may not have performed due to the changed circumstance or unforseen problems, so it may be necessary to replace underperforming plants with ones that worked on the project. If you are unsure of the conditions, choose plants that work in most conditions, but do not lose sight of specialised plants for specialised conditions. Slopes need very drought tolerant plants and wet feet is usually not an issue here, or gullies need plants that cope with wet feet, but also a little drought.