We have grown garlic for many years, but have always been a little disappointed with the results, with a mediocre yield of mean looking bulbs. Last year, we planted both autumn and spring sorts, but the weather was not favourable and the crop very poor indeed. Onions, shallots, and garlic from the autumn sowing suffered particularly with the wet conditions.
Although, like onions and shallots, garlic can be planted either at the end of autumn or early winter, or in the spring, it supposedly benefits from a period of cold that stimulates bulb formation, and an early sowing gives plenty of time for the bulbs to bulk up. There is a tradition of planting on the shortest day of the year and harvesting on the longest, but I tend to plant a little earlier to give them a chance to establish before winter sets in, and harvest a little later. The harvest ought to be guided rather by the state of the plants, digging when the foliage has turned yellow and begins to die back.
Whatever the benefits of an early sowing, being exposed to the weather can be problematic. I suppose cloches might offer useful protection, but have not tried this approach. I have used fleece, attached to a frame, but the results remained unsatisfactory. Though protecting from the cold, fleece does not protect much from the damp, yet reduces air circulation, making matters worse in my view. This season, though, is the first with our polytunnel in use, and last autumn we planted under cover three bulbs of French garlic Thermidrome and one of Early Purple Wight. The results have been fantastic, giving our best ever garlic harvest. The majority of the bulbs are of a good size, much larger than typical supermarket offerings, with juicy, fat, flavoursome cloves.
Of the two sorts, Thermidrome performed best. Several of the Early Purple Wight bulbs were not properly formed, although they still offer large fat cloves of garlic. Although these were ready to be dug perhaps several weeks earlier than Thermidrome, Early Purple Wight is said to be a poor keeping variety, and I am not particularly inclined to grow this sort next year. Thermidrome, on the other hand, I can highly recommend. I am inclined to attribute the much improved harvest to the protected environment of the polytunnel, and plan to replicate this next season.
The garlic bulbs must be dug with some care, as they form surprisingly deep. Once dug, they can be spread out in a warm place to dry. When the skin becomes papery, I will brush off any remaining soil and move to a cool, dark, place for longer storage. We planted some cloves of another French variety, Arno, outdoors in the spring, and it will be interesting to see how these do this year, under what has so far been better weather conditions, although the early cold weather did result in a rather late sowing.