Whether to Support the Foliage of Onions
25th May 2000
My onions are now clearly romping away with the necks thickening up and the leaves beginning to really swell out. There's no doubt that the first sign of really good strong growth on the large exhibition onion plants is when you see deep grooves or dent developing on the large heavy leaves. It's just before this point really that you have to decide whether or not you intend to support the foliage of the onions through the growing season or to leave them alone.
Support for Large Onions
The points to remember are that if you are going to support them then that support has to be effective in order to take the weight of the onion foliage as they grow. Believe me when a good onion plant is really full of foliage there is a tremendous weight to cater for. Some growers us rings made from a very stiff wire and supported by canes whilst others will form a cage with strong string so that the foliage is well supported. Once you have decided to support them then it's better for that to continue throughout the season. Trying to remove it later on will only lead to the heavy leaves falling down and the weight will inevitably mean that they will snap. They can snap off like glass lower down as they are very tender and full of sap and naturally any broken leaf reduces you chances of getting the optimum growth from that onion.
Allowing to fall on to black and white polythene
Personally and mainly because of my heavy commitments to other things, I decided many years ago that I would not support the foliage but rather leave them to there own devices to fall down gracefully on to the black and white polythene. There is however one important factor that I endeavour to control throughout their growing period and that is to ensure that the neck of the onion is kept as erect as possible. What I call the neck is the area from the base of the onion right up to where the bottom leaf is forming from the stem. If this is not kept upright and erect then the resulting developing bulb will not have good shape or form.
When I plant my onions they are removed from their growing pots complete with the supporting green plastic plant support clips that encase the onion foliage. This is done by pushing into the pots two strong split canes along the sides and then two clips are pushed onto the cane in order to from a complete circle around the foliage. Another two are added later on and higher up the canes as the onion grows on in the pots.
Once the onions are really growing away the clips will be gradually released until within a week or so they are all removed. Initially when they are taken away you may well have to use your hand underneath some of the heavier leaves as they slowly bend down in order to prevent them from cracking. Once the foliage has settled down any new growth will then naturally fold over as they reach a certain size and weight with no risk of any severe cracking or splitting.
From this point on keep a careful eye on the stem of the onions, the weight of the falling leaves can make the onion lean over thereby causing the onion to have a mis shaped bulb when harvested. Any bulbs that are showing signs of leaning over one way or the other are pulled back upright in one of two ways. Very often it"s sufficient to very carefully lean the plant over slightly and then push in some soil from underneath the polythene around the opposite side of the bulb to which it is leaning over. This is usually enough to maintain a perfectly erect neck or stem.
If however they have leaned over to an extent that pushing a little soil under the bulb will not rectify the matter then place a short strong split cane about two inches away from the bulb and the opposite side to that which it's leaning over. Attach the larger size clip to the cane and at a point just below the lowest leaf and pull it around the stem whilst at the same time gently and very carefully pushing the onion over and then push the other end of the clip, onto the cane. This will then prevent the onion from falling back and will usually be sufficient after a few weeks to make the onion grow erect at which point the clip can be remove before the onion swells out and the clip itself can become a hazard.
Keep a very careful eye on your plants from now on for the dreaded Thrips, they can usually destroy your chances of getting good sized onions and controlling them is a major problem. You will first notice there is a problem when the foliage starts to take on a silvery look as a result of the incessant nibbling of the young foliage. The damage is usually done out of site as the tiny pest is nibbling away well down into the central young foliage. This little pest is so tiny that it's barely visible to the naked eye, if you are uncertain, take a magnifying glass with you and carefully open out the foliage in the middle and you will see a whole zoo of them crawling around and munching away.
Regular preventative spraying is the answer in order to keep them at bay, however we are not allowed to use commercial chemicals such as Decis or Hostaquick but we can use the commercial chemical Bifenthrin which is sold to the amateur grower as Polysect. Regular use of this product together with blue sticky traps will help to keep them free of this pest. Keep the beds uniformly moist and water as and when the bed needs it, push your hand under the polythene to feel how moist or otherwise the soil is and turn the seeping hoses on if they are on the dry side.