The large exhibition onion plants are now in 3″ pots and really motoring away and very shortly they will have to be potted on into 5″ square pots. The potting mixture that I used at the 3″ stage was the same mix exactly as last year and it really did produce some excellent quality plants. The best onion shape is only arrived at through thorough preparation care, keeping the plant bolt upright will ensure that your harvested onions will have perfect form. Two pests in particular can destroy the onions- Red Spider Mite and Thrips. Regular spraying using Polysect at double strength dose as recommended by the makers should help to make sure that these pests are kept under control.