A 5 gallon nursery can with crammed roots in a south facing spot and only getting handwatered twice a week; you killed it from lack of water, plain and simple. I agree that Kangaroo Paws can be temperamental to grow with regard to drainage and proper watering, but the Anigozanthus flavidus cultivars are among the easiest to grow. Do amend the soils for good drainage, give it full sun and good air circulation and avoid overhead spray on the foliage if you want to minimize the Ink Spot disease, and regularly prune off infected foliage to the ground, especially if it isn't getting full sun and/or good air circulation. I have found that some species/cultivars of Anigozanthus are much more tolerant of clay soils than others, and any of the A. flavidus cultivars are fairly tolerant of clay, as well as it is sloped or amended slightly so that it doesn't stay saturated. Not a good candidate for planting where it gets constant overhead spray irrigation which in combination with too little full sun can lead to the fungal disease. While this plant is rather drought tolerant in the ground once it is established, as a container plant in its original size container from the nursery, twice a week watering in full hot sun just isn't enough, and you cooked it. Get another one now that it has cooled down, get it into the ground in full sun with good drainage, and the twice a week watering regimen will probably work just fine. If you prefer to keep it in a container, buy a smaller one gallon, repot into a larger 5 gallon container, and hook it up to an automatic drip irrigation system so that it gets a little bit every or every other day, or keep an eye on the plant so that it doesn't ever go bone dry between waterings.

Anigozanthus flavidus is one of the easiest to grow, and best to slightly abuse here in northern California, but does do best with perfect drainage and siting to keep it dry and sheltered from cold wet winds in winter. As it is native to seasonally swampy peaty soils in western Australia, it shouldn't reasonably be expected to have much frost tolerance, but it does take short periods of low 20'sF and come back from the roots. In fact, it is often burnt back to the roots to generate fresh foliage free of black ink spot disease, which is also very common on older plants here, and eventually disfigures the plant and weakens it. So losing top growth annually to frost shouldn't be an issue if the plant has strong roots. This plant does best with good drainage, full sun, and good air circulation. It will continue to bloom into winter here if given some protection from extreme wet and winds. If you have room to bring it into a cool greenhouse or sunporch, and treat it as a container plant, you will no doubt have a larger more vigorous plant come summer. If they are available as vigorous one or five gallon plants in spring from California, this might be a more practical way of enjoying the plant. One of my personal favorites, but then they look great here at least 10 months of the year, and are not at all demanding. I highly recommend the cultivar 'Harmony' for deeper, lusher green foliage and beautiful deep orange red stems and yellow flowers on stalks to 5 or 6 feet tall.

First of all, you might want to start posting on the CA gardening forum. There are quite a few SoCal gardeners on it. Second, soil and prep are ALWAYS more important than plants. If you have clay soil it won't drain well and watering so often will create root rot. Yes, new plants need to be watered to establish themselves - so it's a fine line between "watering enough" and "drowning", in this case. Your calla lilies will yellow and go away very soon. They HATE hot soil. They are partial shade plants at best, especially in your area. In coastal CA they bloom around Nov/Dec thru mid-May. "Hercules" gets not only very tall but will grow outwards at a steady rate. I wasn't successful with my own Anigozanthosos (kangaroo paw), but when advice says to prune back after flower, they mean the flower STEM, not the whole plant including leaves. Sage can be pruned almost any time, as far as I can tell. But like rosemary, you want to avoid cutting into the woody stems. Cut it back to a pair of leaves - any pair, just so you don't leave it leafless on that stem. Bougainvillea can be touchy about getting established. They hate being transplanted and it's very easy to harm the rootball because it falls apart easily. Once it's adjusted, you can cut back the watering gradually. "Sulking" won't harm it as long as you water as soon as you see the symptoms of leaf curling, etc. Dahlias are prone to root rot, especially when dormant in winter. With your clay soil you might be better off growing them in pots if you refuse to amend your soil. Watering too often and shallowly is a common error for beginners. Most plants prefer watering less often and deeply, and from underneath rather than above. Good luck!

Anigozanthus is the genus name. Red flowered forms tend to be one of the rufus hybrids - 'Big Red' is a popular selection. Many of the commonly offered varieties tend to be some sort of hybrids.