Exhibition Onions and Tomato Seedlings
25th Mar 1998
The big task this coming week will be to plant my exhibition onions in the polytunnel, I hasten to add however that my soil has been warmed up by the use of soil warming cables. The minimum soil temperature has to be around the 55°F which means that for those of you with no means of warming the soil up, it's definitely advisable to wait until the temperatures are right. The reason that I say 55°F is that when you place the black and white polythene on the surface of the soil, the white side upwards reflects all the heat away which means that the soil temperature underneath can drop by about 5°F and 50°F is about the lowest that I would like the plants to start growing in.
Last October the polythene cover was removed from both polytunnels and replaced during mid February after the Winter rains had washed out any impurities and in particular would have ensured a low conductivity reading. The conductivity reading in your soil is very important if you are growing the plants under cover, this is sometimes called the build up of salts in the soil and if it gets very high it will certainly prevent your plants from achieving their optimum growth potential. If you were unable to remove the polythene, then the beds need to be thoroughly washed out using gallons of water. A soil test afterwards will tell you what your conductivity reading is and it should be as near zero as possible, any reding over five can be detrimental to good growth.
All my beds have been built up using concrete blocks to a height of around 600mm, this means that the soil is very free draining and also warms up relatively fast so that with the aid of the soil warming cables, it soon reaches the required temperature. The first task after replacing the polythene was to sterilise the soil using Armillatox, this was primarily carried out to try and prevent the re occurrence of the white rot that I had last year. This disease can be devastating and I lost 6 onions that had grown to a large size during late June and early July and I"m convinced that it came into the soil via the horse manure that I incorporated.
I have always maintained that the onions should be planted out into their beds from the smallest possible size pot, particularly now that we are using peat based composts as the growing medium. My reasoning is that the larger the pot that they are in the larger the distance is for any new roots to travel from the root plate to the soil in the bed. the compost being peat based will certainly by planting out time be very low in nutrients, so the faster that the roots can get into the fertile soil, the faster they will grow away.
From mid February the artificial lights were changed to 16 hours per day and this was maintained right through to planting time. The bottom heat in the growing chamber was also switched off a fortnight ago so that the plants would slowly acclimatise themselves to a cooler environment. I can get 71 onions in the four beds that I have and they are planted out in two rows in the beds, each row is 18 inches apart and each onion is 16 inches apart in the row.
The second task is to mark out the stations and then using a straight line, the same size pots as the onions are growing in are planted into the soil after which the porous pipe system is laid on top of the soil, three lengths of piping for every two rows. The bed is then covered over with black and white polythene, white side facing upwards, this prevents the soil from getting too hot in the Summer, keeps the soil evenly moist and reduces the need for regular watering, it throws light back up onto the foliage for improved growth and more usefully, you don't have the regular chore of hand weeding the beds.
Of course we can get some frosts, but from my experience here in Anglesey we seldom have any consistent nights of hard frost and I firmly believe that if the root zone is kept evenly warm by means of the soil warming cable, the foliage can cope and acclimatise with much lower temperatures. I have seen the air temperature drop to below freezing on a few nights, yet the plants grew away unhindered and since I have been using this form of soil warming, none have bolted.
My Tomato seedlings are now ready for transplanting, they were sown earlier this month in small trays filled with Levington F2 and the two varieties that I'm growing this year are my own introductions in my seed catalogue. Choice, an F1 hybrid and a Harvest Ripe variety is now in it's third year and I have had many letters from growers who have won numerous first prizes with it. My second one was released this year, another F1 hybrid called Ferrari, this was trialled for me last year by Frank Mercer from the Wirral and was amongst the cards at the Welsh Championships last Summer. The seedlings will be planted up into 3" pots using compost from my Levington Gro bags which will have been brought into the greenhouse a few days before hand to warm up. They will be potted up again into 5" pots a soon as the roots are filling the pot before finally being planted out into the border during mid April.