Working in the Heated Greenhouse
1st Dec 2004
There is always some work to be getting on with in a warm greenhouse at this time of year with the blanch and pot leeks probably in need of some attention. The large onions that you kept back from the shows this year should now be planted back in some compost if you would like the fun and challenge of producing your own seed, or even pips from them.
It's also time to get your order for exhibition shallots in, don"t forget the old saying, plant them on the shortest day and harvest on the longest. Before you plant your shallots it's imperative that each bulb is thoroughly checked over to make sure that they are sound. Take particular note around the shoulder and if any appear to be soft, don't bother planting them as they could well be diseased. I never post my shallots out to customers until later on this month to make sure that if any are going to suffer with fungal disease I can destroy them. It equally applies to any that have prematurely thrown up some green shoots, from my experience they never do well and usually collapse after potting them up.
Pot them up initially in some 3½" pots using a good quality compost such as Levington M2 coupled with some good quality sieved top soil, a ratio of two parts M2 to 1 part soil would be ideal. They don't want too much heat, just sufficient to keep off the frost and very quickly they develop a strong root system. In fact I have often been deceived by just looking at the tops, they may well be showing just an inch or so of green shoots but the roots would have been well wrapped around the pot and often overdue for potting on. At this point they need moving on into a 6" pot and for this mixture I introduce a little more soil to prepare them for the bed that they will be eventually planted in. For this potting, mix 1 part of Levington M3 and 1 part of sieved soil.
Saving your own seed off any vegetable is particularly rewarding, you feel when you later plant them, that you have actually created them yourself!. In my opinion the large exhibition onion is such a vegetable and any time from now is fine to be re planting the best onions that you had last year. From the point at which you lifted the onions, they do need a period of storage so that the bulb can prepare itself for re generation by way of throwing up a seed head.
As with the shallots it's important to pot up only healthy sound bulbs and any that show a really soft shoulder might as well be discarded as they will only collapse later on. If however the outer skin has a bruise or two, then remove a few layers of skin and the bulb will root perfectly. In fact I have often found that by planting a perfectly harvested solid onion with the brown skin still attached, some of the emerging roots have a habit of going upwards between the layers of skin, particularly if the root plate has been trimmed hard back. Removing a few layers of skin off all the onions exposes a cleaner surface area on the root plate from where the new roots will emerge. Pot each onion up into a 4 litre pot using any compost on par with Levington M3, the compost needs to have sufficient nutrients to maintain good growth through to next Summer.
It's important that the onions have a good start in the pots and I place mine on the propagating bench as the bottom heat seems to induce the roots downwards. Don't leave them here too long though, just enough for the roots to appear through the bottom of the pot. They can then be moved to a cooler environment as you don't want the onion flower heads to appear too soon, unless you are prepared to pollinate the flowers by hand.
Some exhibitors grow excellent quality onions from pips, these are basically small baby onions that form on the flower head. These pips, as with leeks, will be an exact replica of the parent onion as they are all clones from the same head. Ronnie Jackson from Cumbria had some excellent specimens this year and was very unlucky to not have a card at the Welsh Branch Championships with them.
More growers should try growing these pips as the one fabulous merit that they have is uniformity, each onion will be the same shape as each other. Don't listen when they tell you that it's impossible to have size on them, Ronnie's were about 23 inches around and you don't want onions for showing much bigger than that. For the heavy onion classes though, the ones from seed will certainly have more vigour and right strain of those are definitely the ones to grow for that class. Some seasons a few onion heads will throw out plenty of pips on their own accord, indeed one year I had them at least an inch long and nearly the size of some pickling shallots. If they don't throw up any pips, deal with them as we do for leeks, trim off all the flower heads and that should induce the bulb to throw some pips.