Pennywort is a sign of bad drainage in the garden beds themselves. So rosemary is a bad choice. Your grasses are also not a good choice - I fear that they will become weedy in your poorly drained soil. You are getting water coming from higher up the slope and the wall is now an obstruction to the flow of water. If you plant good sized gums along your fence-line, these will help to soak up some of the water coming down the slope. And this water may not be above ground, but seeping through the soil. I assume that its clay? I would be using ONLY native plants because they are better suited to the soils of your area. Whenever people have problems with drainage in their gardens, this is the ideal time to use natives. But choose varieties that don't set seed. The grassy plants that you have selected both set a lot of seed - which then become weeds! Plants like bottlebrush, melaleucas - and use the smaller growing forms, leptospermum [tea tree] etc are all good choices for poorly drained areas. But be warned that you cannot use roundup around young natives so hand weeding will need to be done. Clear the area well BEFORE you do any planting and get on top of the pennywort. Maybe retain your camellia - I hate the thought of removing it! But if its not looking good, remove it as it will drag your whole finished product down. Don't use black plastic - its really bad for the soil. Your vinegar spray sounds fine - is this with Epsom salts?. Boiling water is also pretty good as well. But you need to keep doing it regularly. Gardening is not easy in the initial stages, but if you persist, the hard work does eventually pay off!

Given your coastal location and aims for both coherence and low maintenance, you have a wonderful opportunity here to landscape your garden entirely with natives. As you’ve already decided to start with lillypillies (careful to avoid the variety prone to psyllid - the most resistant varieties according to Don Burke are Acmena smithii and Syzygium luehmannii: http://www.burkesbackyard.com.au/fact-sheets/in-the-garden/flowering-plants-shrubs/best-lilly-pilly-varieties/#.Vq0lfMf2PNw), I suggest you refrain from mixing in exotics to any significant degree apart from specimen pots, or other feature items. This way you have control over high maintenance species which should be nurtured for their specialness rather than a becoming a chore to avoid. I spent time visiting friends and family on the Mornington Peninsula this time last year and was shocked at the mindless distribution of what would be considered rampant bushland pests (invasive weeds) in NSW. The entire peninsula seems to boast only remnants of bushland with robust integrity. Agapanthus – because of its hardiness – has decimated vulnerable parts of the NSW bushland (especially in the Blue Mountains), requiring teams of volunteers to hack it out from rainforest and catchment areas in all weathers. Of course aggies are most romantic lining a long gravel path to a mansion, but this does not appear to be your situation here. Forgiveable in past eras, there is now no excuse for beautiful, fire-prone coastal landscapes to be placed under siege by introduced species. A substitute native I have successfully grown is Libertia, which clumps beautifully, is hardy and has a lovely little white star flower in the spring. Herewith some suggestions for conceptualizing a native garden, whose purpose, while often forgotten, is to attract birds and butterflies and to generate beauty and harmony and a sense of peace. It goes without saying that bonuses to the spiritual dimension are the disappearance of weeds and a farewell to mowing. A guiding principle in selecting natives is to select species native to your area first; information is readily available online. It’s not a hard and fast rule, but can save heartache when it comes to planting trees and shrubs that have evolved successfully in other soils and climates yet may fail in yours. Suggest a drive around the area to observe established native gardens to gain inspiration. First off (so long as not near power lines) I’d echo your coastal gums by planting an advanced specimen bang on your front right hand corner boundary, from where you might radiate a rockery. Your front garden cries out for drama, and while a rockery may be your biggest expense, one or two large feature rocks placed among an undulating design can be filled with scattered smaller rocks and a wide range of sun-loving and architectural flowering grasses (e.g. lomandras, dianellas, fescues, grass trees, kangaroo paws, etc), gorgeous flowering native plants (e.g. correas, philothecas, westringias, waratahs, proteas, etc), shrubs (e.g. acacias indigenous to the area), and groundcovers (e.g. myoporum, pratia, and brachyscome, prostrate form grevillias, the beautiful rock cover scleranthus biflorus, etc) will bring endless birds and human happiness. As for shrubs and trees, the choice is endless, thus requiring planning in consideration of the growth habit and life of a tree - which in the case of acacias, may be a mere 15 years. Decomposed granite will keep large and small landscaped areas (such as paths and rockeries) free of weed and also provides nutrients to natives (cautiously spray weeded ground with a strong solution of glyphosate before laying gravel). Be careful not to place too much soil over the tops of roots when planting, as many natives absorb phosphorus this way. Seasol is fine as a wash-through fertilizer after planting, and planting just before rain is due is another handy tip for a nitrogen fix from mother nature. Frequented by nectar-loving and berry-eating birds, the long-lived Blueberry Ash (Elaeocarus reticulatis) has to be one of the prettiest native trees of all, with its grey green foliage all year, feathery pale pink flowers in spring, and blue berries in winter. It can be hedged, but is at its best lightly pruned. It is comfortable in semi-shade, so could be planted as a feature tree out the back, but could also be a stunning success as a hedge from your garage to the letterbox. Grevillias (Mallee Dawn has soft foliage and a lovely pale orange flower) and Callistemons are relatively fast-growing once established and will quickly attract native birds (especially honey-eaters which will then gain confidence to move into other protected areas of your garden; always best to place birdbaths among shrubbery - e.g. the white-flowered Leionema – to offer little birds rapidly disappearing from the Peninsula the protection they need). Victorian Christmas Bush is a mid-height stunner and Isopogon is fabulous planted under banksias and hakeas for a bushy spot. I one saw a gnarled old banksia out front of a house that was probably the most beautiful tree I have ever clapped eyes on, perfectly pruned with its trunk formed like a bonsai writ large). A weeping acacia cognata makes a great corner feature or specimen tree, and a native hibiscus will flower profusely and gloriously in full sun. Shade at back and side cry out for more romance. You might plant native violets to run up the side under a hedge, or to fill a corner rockery out the back. Suggest plant hedges/screens and feature trees first (thus establishing your shade ‘canopy’), and construct a temporary planter box somewhere out the back where you can bring on smaller plants and shrubs while waiting to decide where to put them. The squareness of the back garden can be broken up and softened by strategically placed trees and shrubs, e.g. a large native tree in the left corner, that segues into your lillypillies, under which you could landscape a seating area. You might consider a Kennedia, Clematis aristata, or Pandorea pandorana (Wonga Wonga vine) to cover the side fence behind the garage (and definitely the back shed!). You might add two more callistemons to surround the back shed to conceal it, as well as adding variety and interest. You might infest patches of your back lawn with a native variety, such as weeping wallaby grass (e.g. Griffin). You could dig a shallow trench along the retaining wall and plant a dwarf lillypilly hedge (or substitute, like dwarf acacia cognata) along its length. One might even concede English box for the spot. Native violets/native geraniums (geranium solanderi) will both cascade over the side of any retaining wall, and will prettily flower as well given enough sun. You could plant a white hardenbergia each side of the steps (or even matching specimen eucalyptus ficilfolias!) and consider extending a simple pergola over an entertainment area that looks out over your masterpiece. Trust this inspires a little, Sandman. Keep in mind that the most interesting gardens have three layers: the canopy, the understory and the ground level shrubs, grasses, and ground covers; with the right inquiries to nurseries as to ‘microclimates’ and growth habits you will create a thing of joy – as much in the making as in completion. So far as I know the only other necessary qualification for creating a successful native garden is being a skillful pruner. Natives love to be pruned and shaped, and as long as you ‘prune to the node’, you will prevent die-back and disease, your foliage and flowering will be dense and glorious, and your garden will be the envy of the neighbourhood.

we are in Melbourne ..our last place was all clay ..used to be the old brickworks You'd need to dig down and replace with top soil.. Bird of paradise is quite hardy..Agapantus ..Chinese Elm..loved my ornamental pear ..beautiful colours in Autumn.. pencil pines..pine trees..plane tree if you've got room as they can grow quite tall trying to think of the trees we had at our old place ..Silver Birch..plum is another we don't do much with our plants so the ones left standing we keep kind of miss them some days http://www.abc.net.au/gardening/stories/s2307588.htm

Hi Aravind, Personally I'm a fan of minimising impervious surfaces, and would try to attain different levels of landscaping with native vegetation, lawn & permeable paving. This doesn't sound like what you are looking to do, but if you do go ahead with concreting a large portion of your backyard, keep in mind that water which would have gone into the ground will be redirected to somewhere new. Definitely make sure that the concrete slopes away from your house to avoid damaging your footings/house (instead of the potential termites doing it). Regarding the kitchen, it can often be worth chatting to an architect/building designer if you are likely to do more renovations down the track. They will be able to help you come up with (and draw up) an overall concept so that you know that your kitchen will work with any future renovations and don't end up knocking down or redoing anything, which can save you down the track. An example would be if your kitchen was not in the best location to make use of your living spaces or faced the wrong way. If you were gutting the whole thing, you could be better off moving it now to increase the livability/value later. A joiner or cabinet-maker will be able to go into detail with you and get it built.