Lions & Grasses

Pennisetum clandestinum is largely confined to urban environs in Australia with very little incursion into natural systems thus far, probably due to lack of seed output relating to the genetics of the plant material available:  

http://www.viridans.com/INTRO/urbanweed.htm

Though P/C. clandestinum where present can form dense monocultures and intrude into garden beds via runners and few things seem to eat it from what I've seen, other than some waterfowl on the edges of ornamental ponds etc. 

This can be contrasted with various other Pennisetums which have become serious environmental weeds via airborne seeds.  

I believe much concern pertaining to exotic suburban lawns coming from environmentalists relates to the water, fertiliser and pesticide inputs in particular the creation of oases of green in semiarid areas, and a perception that the land dedicated to the maintenance of manicured exotic monocultures could be perhaps better utilised but each to their own. 

Heaps of exotic plants harbour insects, a review of horticultural and agricultural pesticide sales will attest. Just look at a cottage flower garden, they are often full of life. It is the quantity and type of insects attracted which matters from a bird attraction perspective.   

Much of Australia's small birds are specialised and dependent on small leaf insects such as lerps associated with eucalyts, a forest of Ulmus or Betulas in the burbs will usually be comparatively devoid of thornbills and pardalotes etc. cf. a native euc forest.  

I see no reason why native gardens can't be neat, I often see manicured hedges of Westringia fruticosa, screens of Syzygiums, Elaeocarpus reticulatus and  borders of Lomandras and Dianellas out front of fast food outlets, Archontophoenix, Xanthorroeas, Cordylines in nearly sterile pool-side settings etc. Indeed I reckon native plants have never been more popular and are increasingly mainstream, indigenous gardens though are still yet to be widely adopted in domestic settings in many areas. 

I was not discounting the inputs of agricultural systems. 

I was using the conventionally accepted meaning of 'native' in gardening circles; I don't necessarily agree with it. Most Australians would regard the red kangaroo as a native animal even if it is not indigenous to their backyard. 

The complete opposite is often true for exotics and their pest associations and resultant implications, often only a small subset of the biota typically associated with a particular species is present in its introduced land, meaning a particular pest if introduced can obliterate the host plant due to a lack of natural control measures. This situation can be utilised in biological control operations e.g. cactoblastis cactorum wiping out opuntia spp. as far as the eye can see in Qld, not a likely situation in Argentina.  

The intricate ecosystems associated with any plant species rarely damage it in natural systems or they are at least adapted to periodic denudation and/or possess mechanisms for recovery, granted human disturbance has done its best to upset this balance. 

If a native plant species is severely damaged or disfigured by its native plant pest then I see that more as a symptom rather than a problem generally but so many factors apply. 

Indeed the tough sclerophyllous leaves and natural resilience of many native plant species means that damage sustained by plants from pests is often less noticeable than the big holes in leaves of lush exotic vegetation in my experience. 

You are using a very unconventional definition of native. 

Can there be a relative scale of nativeness? Is a plant that grows a few ks away in Aust more native than a plant of the same genus found on lord howe island? is it more native than a European species? Is a New Zealand species more native in a Sydney garden than a Western Australian species because it's closer geographically (few gardeners would be convinced of this)? Is a Metrosideros more native when grown in Australia than an oak tree because it shares a family with much of Australia's flora? Leptospermum scoparium is a local native species but the specimen in my garden is decended from the NZ population (I don't regard it as native). 

Without using species-specific examples it's difficult to talk in such terms and it's mere trivialities. 

I would regard your Melaleuca as native but not indigenous using conventional wisdom without knowing species and location simply because Melaleuca is a quintessentially Australian genus of the most well known Australian plant family, but it's all just subjective based on one's own definitions and doesn't make it right and I see merit in your own as indeed it could equally be considered exotic and I see no problem with this. 

It can be hard to discern with confidence the invertebrate biodiversity associated with a plant via visual inspection at a given time (invertebrates are usually pretty small), and insect populations attracted to a said plant may well increase at flowering time. 

Melaleuca spp. don't seem too troubled by native pests even in their native ranges in my experience, perhaps because they contain terpenes with demonstrated antiseptic and insecticidal properties, and their often spiny sclerophyllous foliage is often reasonably unpalatable to predators. 

An exotic species (here I mean overseas exotic or non-native 'native') can be just as troubled (or more troubled, or not troubled) by pests as an locally indigenous plant species. Potentially even if only a handful (or even just one) pest species of that plant is present as the site of cultivation (note the pest could be local or introduced) it could do more damage to that plant when compared to an indigenous plant with an associated intact ecosystem of pest species. 

There are few soil conditions where no indigenous species will grow regardless of how much we have tried our best to destroy the soil profile, after all they evolved with changing environmental conditions for millenia. Indeed many species such as Acacias have adapted to colonising  (and improving) some of the oldest and most impoverished and infertile soils found anywhere on the planet and are hence used for rehabilitating mine sites. Some natives will grow on practically pure sand. Site is polluted by heavy metals? There are metallophytes. Soil is destroyed by salinisation? There are an array of halophytes able to cope with this situation. Maybe you mean phosphorous toxicity and excessive associated nutrient loads, the legacy of conventionaly farming and horticultural practices? Many native plants will tolerate phosphorous well despite its natural rarity in the Australian landscape, it's an urban myth and only Proteaceous species that are susceptible for the most part, some are surprisingly tolerant, maybe grow some lusher subtropical species in suitable climates. 

Australian plants can be tough, equally so can many exotics, it's all down to species and circumstances one cannot talk in absolute terms. The pest control inputs of an exotic garden may equal or outweigh the expenditure on an indigenous garden. 

Many exotics (here i mean the stereotypical european plants) are more labour intensive when cultivated in parts of Australia due to higher water requirements and associated inputs due to lacking sclerophyllous tissues and are certainly not advantaged versus indigenous plants, but there are heaps of drought tolerant southern European species which are indeed favoured in regions of similar prevailing climates (but note these plants will not necessarily thrive moreso than indigenous plants).  

I try approach more from a biological and botanical angle but I try not to attach too much significance to subjective arbitrary labels, but they're sometimes practical and useful in general conversation for convenience sake. 

Your Melaleuca is a 'native' plant as understood using conventional horticultural terminology (which I do see the weaknesses in). 

Remember a lot of Melaleucas and Myrtaceae generally have large ranges in Aus-oops this southern hemisphere landmass- and ranges are constantly changing with adaptations, cultivation and habitat destruction etc. 'Indigenous' is perhaps thus a more useful term.  

A lot of the-continent-we-are-standing-on's flora are found no where else, entire generas are confined to this continent as a legacy of its long isolation. 

There is a lot more ecological continuity in the northern hemisphere, say Eurasia by virtue of its geography. 

A gardener in western Europe (Germany) growing Achillea millefolium can regard it as a native plant, as can one in eastern Asia (China), (indeed as can one in North America) because it is indigenous and it's found across the northern temperate region.

I agree growing Davidia involucrata in a western European country and claiming it to be 'native' (as it's from eastern Asia) because if you kept travelling east you'd eventually run into some does seem rather illogical.   

An endemic genus like Persoonia is to me mentally inextricably linked to the landscape of Terra Australis and its ecology, and by extension southern Africa and the broader southern hemisphere generally by means of closely related genera in the Proteaceae which happens to be largely confined to the southern half of the globe. 

Equally the genus Fagus conjures up images of temperate Europe (note 'native' to Europe not political entities found within this geographical area). 'Australia' happens to be an island continent, geographical area and political entity with a high degree of endemism, such usage can be merely practical as its the commonest name for the continent these days, nothing jingoistic is necessarily implied. 

If a rare orchid is native to a region of eastern Bhutan how else do you talk about it? GPS coordinates? How do you feel about state flowers? national flowers? the Lebanese flag?

What about Acer japonicum? Camellia sinensis? Panax vietnamensis? Is all Linnean botanical nomenclature cultural imperialism? Equally is a Maori person referring to Sophora microphylla as Kowhai being nationalistic?