... or to replace a lawn depending on what you would term a lawn or not
When choosing the right grass for your lawn, most people will tell you to consider the following:
1) will it need lots of water? Do you have water restrictions? Do you have low rainfall?
2) what will the traffic be like? Do you have kids or pets?
3) what will the light exposure or shade be like? Will it get full sun for most of the day? Will it get full shade for most of the day?
4) how much time do you want to wait for it to look like a 'lawn'?
5) how much money do you want to spend on establishing it, then maintaining it?
6) how much time do you want to spend on ongoing maintainance, mowing, watering, feeding etc etc?
Blah, blah, blah...
However, what most people will not think of are that the grasses they are using because of their ability to speedily establish, cope with heavy traffic, wear and tear, droughts, shade and regular mowing, are also the ones which are most 'weedy' or 'invasive'.
When choosing a grass for your lawn, particularly if you live anywhere near a National Park, area of special scientific significance, protected vegetation area etc etc, you should also seriously be considering it's characteristics and whether or not you are comfortable contributing to a potential invasion simply to have a nice looking 'lawn'. What would you rather have? Beautiful bushland nearby that you could enjoy in all it's natural glory: for free? Or a lush green lawn all year round?
If you do live near an environmentally sensitive area, Kikuyu as we've all seen, is pretty invasive. It is a listed weed and apart from the risk of it spreading from your garden into the local environment (which believe me, is pretty high even though it doesn't seed because those runners get everywhere!), it will drive you bonkers stopping it from invading your garden and veg beds.
Please carefully look into the properties of any grass you are choosing to ensure you do not personally contribute to a growing existing problem.
In the meantime, you could consider the following alternatives if you do live near an environmentally sensitive area:
Agrostis stolonifera - Creeping Bent - provides a fine turf if you're going for the golf or bowling green type of lawn, though it doesn't do so well in compacted soils. Not a native. Cool season grass. Shallow roots means more frequent watering generally required and it would definitely benefit from under soil reticulation, at least for the summer months. Setting the mower at an absolute minimum of 0.5cm, preferably 2cm or more, will help to allow maximum root penetration and therefore increase ability to cope with drought. Doesn't cope well with wear, but does have a medium salt and shade tolerance, as well as a good frost tolerance.
Austrodanthonia racemosa - Clustered Wallaby Grass - works well for garden lawns and can be blended with other grasses, particularly Microlaena stipoides. Native. If sown pretty thickly, this can give you a good lawn for shallow soils or where you can't water. It is pretty slow growing though has excellent drought tolerance, good salt tolerance, high shade tolerance and is pretty alright with wear and tear. Not so great in shade though. However, it's not suitable if you want a bowling green as you need to keep the mowing height above 5cm for good root penetration.
Dicantheum sericeum - Queensland Blue Grass - hardy and drought tolerant, so usually used for landscape plantings rather than lawns. Native. This is a warm season grass with excellent drought tolerance, low water requirements and copes well with traffic or salt. Not so well with shade or frost however, as you would expect. A mowing height of around 2.5cm is probably best. This is better suited to warmer, drier areas where there are problems with the invasiveness of exotic warm season grasses.
Microlaena stipoides - Weeping Grass - a tussock grass, but works well for lawns in dry, shallow soil areas. Native. There has been a lot of research into these grasses, particularly the Griffin variety, which can create an excellent lawn. It has very high drought, shade and frost tolerance, and is pretty good with the wear and tear. It will look good for a while when water is scarce and also has a medium salt tolerance. Keeping the mowing height to 5cm is best for maximum root pentration.
Poa pratensis - Kentucky Blue Grass - hard wearing so works well for playing fields, parks etc. Not a native. This needs so much water to look good it's rarely considered a good option for a waterwise lawn. It's also got a poor salt tolerance. It's not too bad with traffic or shade, but the main benefit is it's frost tolerance, making it a viable alternative for the cool, wet and often cold areas of Tas and Vic.
Gotta go hang some nappies to dry, but will add more to this later
Now, some of the above grasses come from places where the climate is cool and reasonably moist most of the time. They were traditionally used for lawns here because that was what people used in Europe, where it rains a fair bit more. Although, living in the Dandenongs I can say that it is debatable whether it rains more here than it did when I lived in the UK!!
Cool season grasses are sometimes referred to as C3 grasses, which actually refers to the type of photosynthesis they use. C3 photosynthesis occurs in plants that evolved in temperate to cold climatic zones when air temperatures are generally below 30c. These plants evolved to use this method because they live in conditions with lower light levels and temperatures, along with higher water supplies. It also means that these grasses are less drought tolerant.
Warm season grasses use C4 photosynthesis, which is an adaptation that allows plants to survive where the light and temperatures are generally higher, and there is less water.
For photosynthesis to take place in either C3 or C4 plants, the stomata (pores) of the plants must be open to allow air to enter: CO2 being a critical requirement of the whole process. As photosynthesis takes place during the day, this means that the stomata are open (in most plants) for much of the day. Unfortunately, the air spaces in the stomata are saturated with water vapour, which is course evaporates into the air. This process of transpiration is unavoidable, whether a plant uses C3 or C4 photosynthesis.
Put simply, this means that, under the same climatic conditions, any well-watered lawn will lose water at the same rate, whether it is cool or warm season.
The difference however is that, when water supply is lower, the deeper routed, drought tolerant C4 grasses, are likely to have a better appearance for longer periods. Water restrictions and appearance are the whole reason warm season grasses work better for MOST of Australia.
However, if you live in an area where the temperatures are cooler and the climate is wetter, there is no reason why you shouldn't consider one of the cool season alternatives. Cool season grasses establish more slowly, so it's better to use plugs or instant lawn than sow from seed. Sowing a blend of grasses however can give you a great, functional lawn that is low maintanance and has low water requirements.
Coincidentally, the areas where the cool season grasses are most likely to be a choice worth considering, are the areas where the warm season grasses are proving to be at their most invasive (i.e. Tassie, areas of the Blue Mountains and the Dandenongs etc).
Further note: the native grasses have a very low phosphorus requirement, so will benefit from NOT being fertilised with those nasty chemicals