Show from February 19, 2006

Leaves

Good morning gardeners. Well it's here at last. Winter came for a visit his past weekend with it, the gorgeous sunshine that makes this half of the year bearable for us gardeners. I don't know about you, but these cold, bright days have lifted my spirits and made me feel just terrific! It's nice to have dry roads and clean cars, to hear the snow crunch underfoot and to see the sun dogs in the brilliant clear air. And how about the fabulous sunsets. On Friday, the sun was slipping away on the horizon looking like a huge orange ball of fire just as I left the office. It was lovely.

Still, a couple of weeks of this will be just fine, thank you. By the third week of March, I will be quite ready for spring. An early snow melt and continued warm weather after that would be nice this year. It will be lovely to watch tender young green things emerge from the soil and then to see the trees leaf out.

And speaking of leaves, they are quite wondrous things. If you were to take a microscope and have a good look, you'd notice a couple of things. First, the veins which add structure to the leaf and carry water and nutrients up from the roots. There are intake veins, called xylem, that bring water and minerals to nearby cells and veins called phloem which carry synthesized food to other parts of the plant. There are large structural veins and networks of smaller, finer veins leading to the cells.

Look a little closer now and you will see that there are millions of small openings in the leaf, especially on the underside, that look like pores in our skin. And in effect, that's just what they are. These openings and the two guard cells on either side are called stomata. And this is where some of the real magic takes place, because it is here that the plant takes in carbon dioxide and light for use in photosynthesis or the manufacture of the sugars needed to supplement the water and minerals drawn up from the roots. The stomata also allow for the transpiration or breathing out of oxygen and water, playing a critical part in the ability of the plant to raise water from the ground. The stomata are usually closed when it is dark and open when it is light. Humidity and carbon dioxide levels also affects the activity of the stomata.

So you can see one reason why it is a good idea not to fertilize when the weather is gloomy or in the dead of winter. There just isn't enough hours of sunlight for most houseplants to process the extra minerals you are putting into the soil. This also shows why you should cut back on watering during the winter. When the stomata are closed for a good portion of the day, not transpiration is taking place, meaning the plants are using less water. Of course, if you're growing under artificial light, it's a different matter. But for the most part, wait until the days are longer to start watering more and fertilizing again.

Well, with me today is a man who knows all these things from first hand experience. Good morning, Kevin Twomey from T & T Seeds on Roblin Blvd.

Kevin, tell us what's happening in your greenhouses right now.