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Parramatta and Hills District Group

Group News 2022


Our April walk was planned to be at Vineyard Creek, Telopea but the recent heavy rains had made the track conditions very muddy so it was decided that a walk along a ridge might be a drier option.

There are not too many ridge walks in The Hills as the ridges were originally cleared for farms and orchards in the 19th century and then gradually subdivided for suburbs in the 20th century. However, there remains an excellent uncleared sandstone ridge at the end of Porters Road Kenthurst. This area was also slated for subdivision but community pressure ensured that it remains to be enjoyed by many of us today.

Twelve of us set forth on an afternoon which remained delightfully sunny even though the forecast had been for showers. There have been several fires in this area including 1975, 1992 and 2002. After the 1992 fire, members of the Parramatta Hills Group pegged out several sections which were periodically monitored for regrowth. These records are still held by our group. Unfortunately, the pegs were burnt in the 2002 fire so it is not possible to identify the exact sites.

Apart from one section of the walk where the dominant vegetation is casuarina woodland with little or no under storey the flora diversity seems to have survived the fires.

Tony Maxwell had prepared lists of species likely to be found in the area and the keen eyes of members enabled us to identify 106 species in two and a half hours. Credit needs to be given to Chris Cheetham whose wonderful knowledge and keen eyes identified some of the smaller species amongst grasses on the road margin which everyone else had walked past. This included a largish patch of Pimelea curviflora and an early flowering Tetratheca ericifolia which for a short while was thought to be the much rarer Tetratheca glandulosa. We did see one rare plant though. There were two plants of Persoonia hirsuta.

       Pultenaea tuberculata               Persoonia hirsuta      Melichrus procumbens

Jennifer Farrer

Talk on Shady Gardens by Angie Michaelis 26th March 2022

Angie Michaelis was the speaker at our meeting on 26 March. As well as being an experienced horticulturist she also has a garden with only one small sunny patch.

Photo: Angie's backyard

Inspiration from Nature

When thinking about designing a garden in a shady area it is always good to think about plants which grow in a shady environment. Rainforests are a good source of inspiration. In a rainforest there are many different light levels and layers of plants. There is the canopy above, plants which are growing on tree trunks such as epiphytes and ferns, climbers twining around trunks and the plants growing on the forest floor. The predominant colour is green but there are many different shades of green from green/brown to green/white with an occasional flash of colour. There are also many different leaf shapes and textures. 

Understanding Your Site

What is causing your shade? Is it a solid wall or tree canopy? Is it shady all day/year? Often there will be sun at some times of the day/year. The shade maybe dense or filtered through the leaves of your canopy. Is the problem really shade or lack of water? Often plants struggle more from root competition than from the shade of the canopy.

Possible solutions

  •  Removing trees entirely is not a good idea as gardens feel best with at least one tree to provide shape to the garden.
  •  Broad leaved plants and ferns have evolved to get enough light in a low light environment.
  •  Prune shrubs or canopy trees from below to let in more light
  •  Use tree trunks to display epiphytes
  •  Areas with summer sun and winter shade are the most difficult to manage. The best solution is to plant something which is happy in the sun but not to expect too many flowers because of the shady periods.
  •  Look at ways to increase the water to areas where there is competition from tree roots. Often in these situations it is better to use pots or raised beds.

Plant Selection

 Up High

Use trunks to grow Birds Nest and Stag ferns, orchids, climbing ferns, climbers such as Hibbertia dentata, Pandorea jasminoides or pandorana, Clematis, Eustrephus latifolius,

Understorey trees such as Backhousia myrtifolia, Dodonaea viscosa, Tree ferns

Structural plants such as Cordylines and Gingers

Baskets for ferns or Viola hederacea

The Middle Storey

Shrub Layer Indigofera australis, Correa bauerlenii, or reflexa, Graptophyllum ilicifolium or spinigerum, Hymenosporum “ Gold Nugget”, Rhododendron lochae, Croweas, Boronias, Bursaria, Philotheca, Syzygium, Pittosporum revolutum, Prostanthera scutellaroides, Zieria, Austromyrtus dulcis, Pultenaea blakeyi, Grevillea shiressii,

Structural Plants Cycads

Ground Covers

Hibbertia, Dichondra repens, Violas, Doodia aspera, Adiantum hispidulum and other ferns, Zieria prostrata, Podocarpus spinulosa, Goodenias, Ajuga, Brunoniella, Dianellas, even mosses.

Change in the Garden

Change is inevitable in the garden. Look for different solutions to problems.
Reinvent your garden. Do you need to keep trying to grow plants under a large tree. Maybe the solution is paving, a seat , a sculpture or a pool.

Talk by Prof. Michelle Leishman 26th February 2022

    At our February meeting, the speaker was Prof. Michelle Leishman from the School of Biological Sciences at Macquarie University. As well as being a botanist, Michelle has extensive knowledge of climate change, particularly its effects on plants and the urban environment. She started her talk by reiterating some of the irrefutable facts about climate change, illustrated with graphs. We know that the average temperature of our city is rising, and that average rainfall is falling, particularly in our far western suburbs. What can we do now to ensure our suburbs remain liveable despite these facts? It is now proven that on hot Summer days, leafy green suburbs remain cooler than those with little vegetation and open parklands. Aerial photos with heat-sensitive cameras clearly demonstrate this. To counteract climate change we need to increase areas of vegetation between our buildings and expand current green spaces. As housing blocks become smaller and houses larger, there is little space left for trees or any living plants.  Planning laws should change to reflect the need for increased green space in the future. Tests show that trees reduce temperatures more than green grass, by providing shade. As well as lowering summer temperatures, trees help combat pollution, reduce carbon dioxide in the atmosphere, provide habitat for birds and other animals and have beneficial physical and psychological effects on the human inhabitants. This latter fact was clearly demonstrated during COVID lockdowns.

    These factors lead to difficult decisions about what to plant to increase urban vegetation. Damage to old established trees has already been seen during heat waves, with leaf burn and even plant death. What we previously planted as street and park trees may no longer cope with increasing climate change. The need for evidence-based decisions has triggered the WHICH PLANT WHERE project. For about five years, Michelle has been heavily involved with a group of researchers, studying and testing a large number of native plant species, looking for resistance to high temperatures and low water availability. The results have lead to the development of the WHICH PLANT WHERE website, which is to be launched in March or April this year. The team has incorporated test results with facts about the occurrence, natural habitat, rainfall and usual growing conditions in the wild of a very large number of native plants. The collated information is being used to recommend which species to plant in a certain area. Some further specifics were added, including a description, size and shape, whether the plant has poisonous fruit, or is likely to drop large limbs.

    In the WHICH PLANT WHERE website, you can enter a postcode and be given a large list of appropriate plants. Your search can be narrowed down by adding further requirements, eg asking for a shrub or tree of a specific size, and choosing whether it is for a home garden or a public park. The listed plants include further information and a photo. The results have been further divided into how hardy a species is likely to be under future conditions. This is done with a “traffic light” coding, green for good, orange for not as good and red for not likely to do well. This coding has three time zones, namely now, in a few years, and in many years. Some recommended species will be designated “green” now, but may in the long-term be in the “red” category, as climate change worsens. The website covers the whole of Australia, suburban and rural, including all postcodes. Of course, conditions can vary in a suburb and also in a home garden, so the website does have limitations. However, this will be the only reference available for information which considers the effects of climate change on the growth of a native plant.

                                                                                                             Pip Gibian

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