12th Feb 1997
It hasn't half cost me some money to keep both my twelve foot by eight foot greenhouses heated so far this year, but when they are all full of plants, some of them destined for Chelsea in May, the commitment has to be maintained. Although we rarely have more than a fine covering of snow in Anglesey, thanks in the main to the Snowdonia mountain range that seems to take most of it off us, we do suffer from freezing temperatures that are increased with the winds chill factor from the sea. Rarely were temperatures above freezing for a whole month from around mid December to mid January, so in order to try and save some money the thermostat was lowered by some two degrees at night time.
The growing cabinet that I have now constructed from hardboard has certainly been helpful in maintaining temperatures at a reasonable cost, in the main because every hardboard panel has been covered with the silvery reflective material which is bonded onto some thin polystyrene and glued in position. The onions and leeks therefore have never suffered and are really growing away well. My own selected onion seed are very vigorous and were potted up into 2½" pots during the first week of January and the rate of growth is phenomenal when given artificial light for twenty four hours every day, right from the first day they popped their heads through the compost.
In a weeks time the lamp will be put on a time switch so that from around the middle of this month they will have a sixteen hour lighting period from five in the morning through to nine at night. From around the end of the month, depending on the weather, the panels forming the growing cabinet will be removed so that the plants can benefit from the increased light levels that we should be blessed with from March onwards. It never ceases to amaze me how strong sunlight really can be and how well plants respond to it. I can go into my greenhouse in the dead of Winter and be nearly dazzled by the strength of the artificial lights, yet on a good clear sunny day when the covers are removed you can hardly see that the lamp is on at all.
The onions will now be potted up into what will be their final pot in my case as they will be planted out directly under covers towards the end of next month. The pots that I have always used are five inch square and the compost mixture will slightly alter with the introduction of more soil so that the plants root system can get used to growing in a medium not much different to that which they will be planted in under cover.
The potting mixture is similar to the one that Mel Ednie uses and is made up of 4 parts Levington M3 or SHL professional potting compost, 3 parts sieved soil (not too fine, a ½" riddle would be ideal) and one part moistened Vermiculite. It"s very important not to get your mixture too fine, they really prefer to grow in a rough type of compost, effectively emulating the conditions in their growing bed. Make sure also that all the material is at the same temperature that the plants are growing in, so get your compost inside the greenhouse in plenty of time. Although the increased proportion of soil will probably make the growth rate slower whilst in the pots, the plants will be firmer and sturdier than those grown in a peat only compost and the eventual growth in the beds will be a lot faster, firmer and healthier as well.
When potting on I always make a mould in the compost using the pot that they a currently growing in so that you simply drop the plant into the prepared mould in the five inch pot, give it a firm tap and moisten the compost using water at the same temperature as the plants are growing in, the roots will quickly work their way into the new fresh compost. Finally do make sure that the plants are well supported so that the onions grow perfectly erect, ideally using the green plastic plant support clips.