Thank you, AnneB and MrDog, for the suggestions. I’ve always grown hardneck varieties, but not some of these.They always seem to start off well but then stall, even if they’re very well-fed and watered copiously. I end up with small bulbs (tiny when dried!) which are strong in flavour, bur very very fiddly to peel! I’m obviously going wrong somewhere.
It may be because I have a clay based soil, but I rarely find it necessary to water my garlic, only in very dry conditions. I give them an occasional sprinkling of chicken manure pellets.
Rossa di Sulmona is a hard neck garlic but the others, Early Purple Wight and Mersley Wight are sofnecks.
If you have white rot, it might be worth a go growing in tubs. I have occasional problems with white rot but keep it at bay by watering my raised beds with a garlic mixture when they become empty before planting with something else. The theory is that the white rot thinks it is dinner time, but there is nothing for them to develop on once the garlic mixture disappears and the white rot then dies off. It sort of works, enough for me to continue to grow onions, garlic and leeks with reasonable success with only 1 or 2 plants affected each harvest.