Greenhouses full in October with Leeks, Onions and Geranium cuttings
17th Jan 2002
Who would think that my two greenhouses would be getting quite full at this time of year what with a good mixture of leeks and onion plants as well as cuttings of geraniums etc., there will soon be very little space. Both greenhouses are heated with 3 KW fan heaters and I have to say that a heated greenhouse today is a must for the keen vegetables exhibitor. There is no way that we could stage the quality onions and leeks that we are doing without some form of heat.
Heating and Ventilation
The sensible use of heat goes together with good use of the greenhouse vents as well in order to maintain a buoyant atmosphere in the greenhouse that the plants really thrive on. Of course if you are using a paraffin heater, whether it be a yellow or a blue flame kind, it is imperative that the vents are opened at least an inch or so to make sure that no build up of harmful fumes and gases affect the plants growth.
Many years ago when I had a double burner yellow flamed paraffin heater I experienced the worse scenario with them which seems to affect badly both leeks and onions. The tips of the leaves of both young plants were turning yellow and growth seemed to be impeded. It turned out to be a lack of ventilation in the greenhouse to allow the fumes to escape and those fumes were slowly but surely affecting the plants growth. It took me a while to understand the need the need to open up some of the lights at night, even when frosty and thereby letting some heat out, whilst at the same time trying to maintain an adequate growing temperature. It was at this time that I decided to invest in bringing electricity down to the greenhouse and purchasing an electric thermostatically controlled heater.
My large onions were sown just before Christmas in my propagator and germination was very good indeed. They were initially broadcast sown in some Levington F2 and covered over with fine Vermiculite and are now ready to be transplanted into small multi cells. I am convinced that a relatively small growing cell is a must initially rather than moving them immediately into a three inch pot which will be far too big and can hold too much water at the initial rooting stage.
Transplanting into Small Multi Cells
For a number of years now I prick mine out into Multicell 40s, in other words forty individual little pots linked together made from thin plastic that fit into the normal full size seed tray. To be honest I thought that these were the smallest practical size that there was until I saw some 60 cells per tray and last year I gave these a go. I was very pleased with them because the onion plants seemed to pick up faster with these and also seemed to maintain a more upright posture than in the others. This year all mine will be started off in 60s and from these will be transplanted into 24s and then 15s or a 3½ inch pot.
One word of caution however, you do need to be quite vigilant with the watering as the cells are smaller and therefore will dry out faster. This though can be a boon as the cells seem to keep drier the root system develops faster, stretching out and searching for moisture which is certainly a good thing for them to do. Onions and too much water definitely don't go together and the secret is to maintain the young plants in a condition that they are always just on the moist side.
To make sure that this happens I always use a small watering can that has a narrow orifice for the water to pass through so that I can easily control the watering. Never use a large can and water all over the plants, that can be a disaster, the last thing plants want is to be kept wet all the time. Water each and every cell as and when they need watering, this can be quite time consuming but will certainly pay dividends as the onions grow on with each and every seedling in the cells having the potential for potting on.
Once I have transplanted the onions, I shall then proceed to sow some more, not more of the large exhibition type but onions for the under 250gram classes. These need to be sown early so that they can be planted out in the polytunnel during early April as fairly large plants thereby enabling you to harvest them at the right size from the middle of June onwards. This will ensure that the onions eventually staged will have the right sort of skin colour that resembles a well harvested onion.
The variety that I shall sow will be the latest new cultivar in my seed catalogue called Tasco and this one was in the cards for me at many shows last year. It is one of the nicest onions to grow as it has a very erect habit with the foliage standing bolt upright. Tasco is a high yielding early variety that provides attractive bronze shaped bulbs with medium term storage potential. However the biggest plus with this onion, particularly for some growers on allotments who have been devastated with downy mildew over the past few years, is that the vigorous plants have a very waxy foliage providing good tolerance to this disease.