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The newspaper headlines read - ARE WE TO SEE THE DEMISE OF THE SCOTCH TOMATO? Our man put two and two together and as a result, in 1978 I left the college and joined the whisky company to manage the project. We finished up with 1.25acres of glass and 0.5 acres of polytunnel. The set-up was heated by waste energy from the distillery and to top that off, we collected the effluent gases from the fermentation process and bled them into the glasshouse atmosphere during the hours of daylight because of course they were high in carbon dioxide! The project ran for 15 years, it was 20 years before it鈥檚 time. At it鈥檚 peak we were producing in the region of 200 tonnes of tomatoes annually.

My own crop of Shirley Tomatoes about 3 years ago (white polythene on the floor to reflect the light, especially important in the early season)

Now to my point, if we were to catch the high price period for home grown tomatoes, we had to plant the crop in February. We had to maintain a night temperature of 15掳C and a positive day temperature of 21掳C.听 That was NOT an easy task as we were breaking new ground on the heat supply side.听 So there was I on a February night, the man himself visiting to see how we were progressing, stood among young shivering tomato plants with the temperature down to 7掳C听 鈥淲ill this kill them?鈥� he asks. 鈥淣o鈥� I replied, 鈥渂ut it will certainly slow them down and as a result we will not meet our target for the first pick and that will surely affect the budgeted returns!鈥�

Deadlines don鈥檛 affect those of us who grow a few tomatoes in the glasshouse at home. My point is, however, we should realise that temperatures play a vital role in how well the plants will crop. In a cold glasshouse, you have to take what nature gives you, nights are normally cooler than daytime but the bottom line is, if you are prepared to use a small amount of heat, results could be much better. I would suggest that we should be able to give the crop a night-time temperature of 10掳C, a little more than that would be good. Now to that day temperature - you will note that earlier I used the phrase 鈥榩ositive day temperature鈥�. That simply means, as soon as it's daylight, we need to see the temperature rise and whilst we aimed for 21掳C commercially, 16-17掳C would be good for your crop and the sooner the daylight temperature reaches the required daylight level the better. If it is a dull old morning, that day temperature target might never be reached! For balanced growth, there has to be differential between night and daylight temperatures of about 6掳C to help maximise crop potential.

Jim McColl MBE presents 主播大秀 Scotland's the .