5th Apr 2001
My growing cabinet has now served it's purpose for another year and the surrounding hardboard panels that form the outer skin have now been kept. Next year though I will have to make some new panels to surround the steel angle iron that forms the skeleton of the cabinet. The hardboard ones have now buckled and some have even started to rot away so the next ones will be made from thin plywood with the same type of polystyrene foil glued on to the internal faces. This material has really worked well for me as the light is bounced off it and distributed very evenly right through the cabinet, even to the furthest corners.
Steel Angle Iron
The steel angle iron is a permanent fixture running along the full length of one side of my 12 ft greenhouse and 3 ft in width. The top section has been constructed in such a way that the strengthening pieces going along the width of the cabinet are the exact length of a full size seed tray. These seed trays drop in between the wooden battens going across thereby allowing any seedlings to be up close to the glass and daylight giving me nice strong sturdy plants.
The two SGR 400 watt lamp unit will remain in position throughout the year so that setting up the growing area next year can be achieved relatively quickly with no hassle. One thing I have learnt this year is the importance of changing your Philips SON T Aggro lamp within the housing on a fairly regular basis. I was unaware that these lamps have only a certain number of hours of working life before the blue light spectrum deteriorates to such an extent that they are no longer of any real value.
I began to notice a couple of years ago that the neck on my onions were getting rather long and I put this down to having too many plants too near to each other in the cabinet thereby drawing upwards to the light, the resulting bulbs however were fine. Last year was even worse, the necks on a few of the onions were over four inches tall and some of the resulting bulbs were too tall for my liking. Having made some enquires I was amazed to learn that these lamps only work at their optimum for 2,000 hours before the blue light spectrum starts to diminish. It"s the blue light within these special lamps that control the growth of the plants and keep them at the height that they would grow at under normal Summer growing conditions.
My immediate thoughts were that 2000 hours would last me many years until I sat down and roughly worked out how many hours the two lamps had worked. They must have been set up about six years ago and for the first four years they would have been on for 24 hours a day from early January through to the middle of February and then reduced to 16 hours until the end of February and then to match daylight hours, approx. 12 hours, until the middle of March at which point they would be switched off.
This means that for the first four years they were on for 24 hours a day for 7 weeks = 1,176 hours. They were then reduced to 16 hours a day for two weeks = 224 hours and finally further reduced to 12 hours a day for two weeks = 168 hours, a total 1, 568 hours per year. As this went on for four years they worked for 6, 272 hours.
The last two years, both the onions and leeks have been grown at 16 hour days from January through to mid February, 7 weeks at 16 hours = 784 hours. From mid February to mid March the lights were reduced to 12 hours, 4 weeks at 12 hours = 336 hours, a total of 1,120 hours per year. As the lamps were on for two years they therefore worked a total of 2,240 hours. The grand total of hours worked by those lamps over the six year period was 8,512 hours; give or take an hour or so!! Four times longer than the recommended period, no wonder that the plants were really growing quite leggy.
I changed both lamps (lamps is the proper name for what I commonly call bulbs; I was told by a technical gentleman at Philips that lamps fit into the housing and bulbs are things that are planted in the soil to produce flowers!) last December and the result was nothing short of amazing, the leeks and onion plants are the best ever, really good growth and the stems are strong and sturdy. This seems to infer that if these lights are changed after two seasons of growth, then the need for having strip lights around the bottom of the growing cabinet, just at stem level seems to be unnecessary as the growth is sturdy enough without them.