Sunday, November 8, 2009

Light & Heat = Growth

We haven’t had the best week at Scotsburn. The burst of warm, humid weather last weekend produced a phenomenal growth spurt in all of our plants. Contradictory as it may sound, this is something we just don’t want. Our primary business is growing seedlings and we spend the majority of our effort slowing seedlings down so that they will last longer once we send them off to the garden centres. Anyone that has grown a hanging basket for our Great Victorian Hanging Basket competition will understand just how frustrating it is trying to speed up or slow growth when you are working to a deadline.
How do we manage growth? Primarily with water and food. Just restricting the water – allowing plants to wilt a little between irrigations is a great way to tone them up. The amount and type of fertilizer used is also essential to controlling growth.
A gardener or nurseryman must keep in mind that the water and fertilizer we apply don’t directly feed our plants; they fuel photosynthesis. Photosynthesis produces carbohydrate that actually drives plant growth and there are two essential elements to the process of photosynthesis that I haven’t mentioned yet… light and heat. Please note these are separate items. Fertilizer and water that were only adequate a week or so ago are suddenly more than enough when the photosynthesis process becomes more efficient with additional light and warmth. Boom! Plants are jumping out of their skins. When you want quick growth, it never happens. When you don’t, suddenly you can watch them grow!
Of course we are dealing with growing organisms and at least four variables so the answers are not always so directly obvious. Too much light and heat will shut down photosynthesis so don’t feed plants on hot days. Too little light and warmth – think mid winter - have the same effect, that’s why we have glass houses. Greenhouse owners though don’t necessarily have all the answers; without additional lighting, extra heat and fertilizer are a waste of time.
By the way, the other way to control plant growth is to use PGR’s (Plant Growth Regulators-plant hormones). Our policy is to avoid PGR’s where possible and never to use them on our vegetable crops. Is this entirely logical? Possibly not, but whenever I ask gardeners the response to PGR’s is nearly always strongly negative.
Does any of this affect a home gardener? Not much, just don’t feed your plants in the middle of winter or high summer for that matter. But you might be interested to know why your plants have suddenly gone into overdrive.
Why did I tell you this long, complicated story? Well the growth spurt in Kerry’s Tomatoes at home prompted another idea altogether and that idea needed some background. Then I got carried away, so I’ll talk about pruning Tomatoes later. In the meantime I’d welcome any thoughts or comments.

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