[Aeneas]

My onions have not developed well this year. I normally plant sturon, centurion and red baron and generally get good sized, well formed bulbs. However this year the bulbs are generally small and elongated with only a small proportion of good size, mainly the red barons. The sets were planted in early March and seemed to develop well with normal leaf growth. The leaves began to wither in early to mid July and the bulbs, such as they are,have now been pulled and left to dry. My question is: could the problem with development be due to the dry spell in April and May, or alternatively due to the wet, cool spell in June and July?

[cooler]

It is important that the soil be kept moist during the onions full period of active growth. If you had allowed the soil to become dry this may be a main reason you have smaller bulbs.

Crop rotation is important too as onions are heavy feeders. Did you rotate the location of your onion crops? You could possibly plant beans or peas in that location next year.
It is very important that good reserves of phosphorous and potassium be available in the soil for good bulb growth. Soil low in Potassium can also result in poor bulb formation.