If you are not ready to plant immediately, or prefer to plant a more advanced plant, you can pot the tubestock into a 140mm or larger container. This is also sometimes helpful when growing difficult to keep alive plants which survive better in the controlled conditions and perfect drainage that you can achieve in a pot.
Always use a quality potting mix, not garden soil, and add a low phosphorus slow release fertilizer at a low rate. It is preferable to buy a potting mix without fertilizer and then add your own to avoid the possibility that an incorporated fertilizer has dumped excess nutrient into the mix. As a general rule it is best to use caution when feeding native plants. 3 or 4 grams of 9 to 12 month slow release native plant fertilizer per litre of potting mix is usually adequate for satisfactory growth. If the middle to tip of the older leaves appear to be sunburnt, you probably have too much fertilizer in the mix.