Being native to both NZ and Australia (also native to Japan and other continents) Tetragonia tetragonioides is known locally as both NZ Spinach and Warrigal Greens. Either way its an excellent tasty alternative to the usual Spinach and Sliver Beet leaves.
It has oxalates in the leaves so needs to be briefly blanched for just a minute before eating.
It’s a very low growing scrambling plant and loves having a nutritious soil and lots of water and sun, but also seems to tolerate half shade and is useful to grow in damper areas around and under fruit trees etc. However I have seen it growing naturally in some pretty inhospitable places especially on coastal cliffs. It does seem to tolerate or even like fairly high levels of salt so a good regular sizeable dose of seaweed solution is useful to help with growth.
The seeds can take some time to germinate (sometimes a few weeks) and its worth pre-soaking them before sowing to help.
Other species in the same genus are worth a try too like the NZ and Australian native Tetragonia implexicoma or bower spinach – which is often mistaken for tetragonioides.
It is interesting to note that even though it grows in places like Japan and South America it is most commonly known in the English speaking world after it’s botanical discovery and binomial identification in NZ.