Potato onions. I bought a really large salad onion from an organic shop and planted it in my polytunnel. I planted six potato onions around it to try and cross them. The idea is that if i cross the two, i might be able to grow the seeds and obtain a new potato onion variety that makes larger onions. For doing this, according to Carol Deppe and her excellent "Breed your own vegetable varieties" book, it would be a good idea to pollinate the potato onion with the salad onion pollen. The reason for this is that the female parent that makes the seeds should be the variety that has the important genetic traits. If both make seed i will try and grow all of the seeds to see the difference.