Peak Growing Period for the Large Exhibition Onions
19th Jun 1997
re now fast approaching the peak growing period for the large exhibition onions and from now on they should be really putting on some weight. Depending on the growing conditions each onion could increase in size by anything between 2 to 3 inches in circumference every week and it really is exciting to go into the polytunnel with a tape measure every few days to make a note of their progress.
I have found over the years that a well kept gardening diary can be invaluable and every time I measure the onions it's recorded so that I can compare the current seasons growth rate with previous years. Make sure that you measure the same onion every time and I select one that looks an average size for the whole bed rather than the largest. I have a set of Diaries going back over twenty years and on a wet murky Summers evening I will often thumb through the pages just for interest and to compare seasonal variations.
Polythene Sheeting and Soil Warming Cables
This years growth is the best ever having had nice strong plants to plant in the polytunnel on March 17th; a total of 71 plants went into the four beds. There"s no doubt that removing the polythene sheeting from both the leek and the onion tunnels have made a great deal of difference as have the underground soil warming cables. The plants never looked back from the day they were planted from their 4" square pots and I recorded in my diary on the 28th May an average measurement of 13½ inches circumference. This means that there are a few in the bed slightly larger and this is the earliest that I have ever had this size, I can only hope they keep on growing.
Tender Loving Care
A little bit of loving care and attention from now on will work wonders so that towards the end of July I shall be able to lift some super specimens. As the onions are now increasing in weight daily it's important to constantly keep an eye on each plant to make sure that they are growing perfectly erect. For instance on my return from Chelsea I noticed a few plants were leaning over slightly so soil was removed from one side of the onion with my finger, the onion was then gently pushed over until upright and soil packed underneath the other side. This I feel is very important if you are to harvest perfectly uniform bulbs with good form so that the onion is evenly balanced all over.
Undoubtedly my wind up curtains on both sides of the two Polytunnels have proved to be a great help, they are wound down every morning if it looks like being a hot day and the gentle breeze that blows through the remaining fine green plastic mesh is like a tonic for them. During the first week of June a fan was also placed at one end to move the air around as well as keeping the temperatures as low as possible.
When my onion tunnel was delivered by Northern Polytunnels I had a bit of a shock to realise how high it was going to be, my main concern was that it was going to look like a pavilion at the National Eisteddfod! however this height has been worth it"s weight in gold. Heat of course rises and at the peak of Summer, on really continuous hot days and in low structures, this heat can be unbearable for the plants and can indeed have an adverse effect on them through speeding growth to maturity before they have found their optimum size.
Another good sign of a potentially good bed of onions is that the neck of the bulb in the early days are only slightly less in diameter than the swelling base this means that you can eventually expect some large specimens. Even though for exhibition we will ultimately be looking for thin necked large bulbs, we don't want that criteria too soon. Onions that are bulbing out with a relatively thin neck early on in the season seldom make top sized bulbs and growth will very quickly slow down.
A Word of Caution
Finally a word of caution, just because your plants are growing well you may be tempted to give them a liquid feed; don't; leave the plants well alone and rely on the thorough preparation work that you carried out during Winter and Spring. The last thing that good growing onions need is a boost to growth when they are already taking up every available nutrient within the bed.