Show from Aug 5, 2007

Good morning gardeners. It’s another beautiful fay in Manitoba. the heat wave continues today and I hope it will continue tomorrow as I am having a barbecue for the cousins in our family. They have a raft of little boys who love the pool, so warm weather would be welcome.

Speaking of heat waves, there are a few problems in the garden associated with the hottest days and one of them is leaf scorch on some plants. A few of my more sensitive hostas have a touch of leaf scorch and a listener emailed me some pictures of her echinacea, which were also suffering from leaf scorch. This is not uncommon in echinacea. They will also wilt on the hottest days to revive in the evening dew. Watering is the remedy.

Gardeners m ay be noticing cracks in the earth now and this is particularly evident in soils that do not have adequate organic content. Nor does it take a lot of organics to keep the cracking at bay, but that’s an issue for next spring. for now, adding mulch will help to keep moisture in the soil.

We often overlook what’s happening in that bottom half of our plants – the part that grows downward under the earth. Here, if it’s healthy, the earth is a beehive of activity, not the dead thing that we sometime observe it to be.

Any square inch is alive with millions of insects ranging in size from earthworms, slugs, snails, ants and spiders, to tiny mites and springtails, to microscopic life such as bacteria, yeast, algae, fungi and protozoa and, we are told, even sub-microscopic life we have yet to identify. They all do their part in keeping the soil healthy and usable by the plants that grow in them.

In a single gram of soil, there are up to 3 billion bacteria, doing such useful things as “fixing” nitrogen in the soil. The bacteria essentially form colonies around the roots of plants from the legume family such as peas and beans and the imported caragana. Here they convert nitrogen from the atmosphere into nitrogen-containing organic material.

There are also certain types bacteria that transform nitrogen into nitrates to help plants grow or return nitrogen to the atmosphere.

The soil is also alive with fungi. Fungi, including yeasts and moulds, can be either parasites that cause damage to plants or they can turn into delicious edibles such as mushrooms. Like us, and unlike plants, they can’t use sunlight as a source of energy. We have to eat to other animals or plants to develop energy and fungi essentially do the same thing order to grow and spread. Fungi grow by sending out long thin threads called hypha. Groups of these are called mycelium, which is what mushrooms are. Did you know that fungi bridge the gap between plants and animals, being neither. They are actually in a class by themselves.

I have told you before about mycorrhiza, one of the most fascinating fungi. Mycorrhiza have a symbiotic relationship with plants and they send their mycelia to invade the root hairs of plants in order to obtain carbohydrates, because remember that fungus needs to eat to survive. But the roots also benefit, getting access to nitrogen and moisture and other mineral nutrients from the activity of the mycorrhiza.

In trees, the mycorrhiza create a large underground network increasing the feeding range for the tree roots, and even allowing trees to communicate with other and certainly to share food and water.

Now, why does all this matter to you and me? Well, the more we understand the better able we are to make decisions about planting and growing, without having to look up the directions.

But it also turns out that not all that lives in the soil is good stuff for plants. In fact, it is now understood that instead of plants “using up” the nutrition in a given plot of land, what is in fact happening, is that plant pathogens build up over time and out- compete the plant life. That explains why the cultivated plant does better in the garden plot which is constantly being amended than it does in the wild. It is also why Farmers rotate their crops and it is why foreign species often become invasive when introduced to new territory – they have escaped their pathogens! (University of Guelph).