Potato onions, unlike shallots that can be grown from seed and division, don’t go to seed they just multiply, so will disappear from your garden if they are not replanted. This is a shame as they are useful, mild, disease-resistant and long-keeping and if what I read is true, Australia is one of the few places in the world where they are grown. This is a good time of the year to plant them, so (sow) if you have any why not give them a try.
Plant them in an open, sunny, well drained part of the garden, preferably where they have not been grown for about 5 years, somewhere you have grown nitrogen hungry crops like leafy greens or brassicas is good. Just screw the bottom half of the bulb into the soil, so that the necks are left out of the ground. These should be ready to harvest around Christmas and have increased to between 10 – 20 bulbs.
It is not a good idea to apply fertilizer like manure or blood and bone at this time, as they can cause issues with maggots, a serious pest for onions. High nitrogen fertilizers may make the bulb big and soft, which means they won’t keep as long – which is why it is good to have planted them in the same patch where your leafy greens and brassicas where, as they will have taken up much of the nitrogen.
However, onions do love lime, so if needed put some of that into the bed.
And remember, garlic is another type of onion that can also be planted now. Just take an individual clove and push it into the soil so it is just below the surface. They should sprout within days and will eventually go to seed, but this will not impact the yield or how long you can keep them.