How A Fungus Can Be Beneficial To Growing Plants In Your Landscape

For millions of years “mother nature” has done a superb job. Just look at our relatively undisturbed national parks and other natural habitats that have been preserved for our enjoyment and you will see healthy plants. “Mother nature” has produced a living soil, filled with wonderful microbial populations of beneficial bacteria, fungi, nematodes and protozoans that supply the plant with all of the necessary nutrients for healthy growth. In your last copy of the F. G. bulletin we talked about the beneficial soil bacteria; now, it’s time to learn more about the beneficial fungi in the living soil. So, the answer to the question “can a fungus be beneficial to growing plants in your landscape” is yes.

The beneficial soil fungi are called Mycorrhizae, pronounced my - core - rye’ - zee. Scientists have determined that probably more than 98% of all the plants in the world have a mycorrhizal association. The actual functions of the mycorrhizae are as follows:

1. Aid in the faster absorption of water and nutrients from the soil beyond the normal root zone.
2. Help protect the roots from soil pathogens.
3. Reduce water and summer heat stress.
4. Extend the normal root zone
5. Increase tolerance to heavy metals, saline soils, and drought.
6. Improve the plant’s tolerance to extremes of soil acidity and alkalinity.
7. Improve yields of fruit and vegetable crops
8. Help to establish root systems in newly transplanted plants
9. Promote more and better root and shoot growth
10. Reduce fertilizer requisites by half or more, once established

Can plants survive without mycorrhizae? Yes; nurserymen for the most part do not inoculate their sterile soils with mycorrhizae and yet they produce some very nice plants: However, when those nice plants are placed in your landscape, some decline and die even after our best efforts to keep them alive. What happened? Since our highly alkaline landscape soils are so different from the plants’ original soil, they could not adjust. One of the functions of the mycorrhizae is to improve the plants tolerance to extremes of soil acidity and alkalinity. You might ask, doesn’t my soil have mycorrhizae? Well, maybe yes, maybe no. If your house is newly constructed the answer is no; mycorrhizae are found only in soils where plants have been established for long periods of time. If your house was built some years ago, some mycorrhizae have probably moved in, but in many instances it is hit or miss as to whether or not there are enough mycorrhizae in your soil. Remember, “mother nature” took millions of years to develop the mycorrhizae in natural habitats and your landscape probably does not fit into that time frame.

What are mycorrhizae? The word mycorrhizae is derived from two words “mycor” which means fungus and “rhizae” which means root. Put the two parts together and we have “fungus root”. Mycorrhizae form a symbiotic relationship between the fungus and the root. When the fungus is present and the symbiotic relationship has been formed, the benefits to the plant as described above will occur. A recent, as yet unpublished experiment on Lychees conducted by the University of Florida in Homestead has shown a 26% increase in growth in inoculated versus non-inoculated, container grown trees. At the present time research on mycorrhizae is being conducted in many countries around the world. Just log on to the Internet and do a mychrrhizae word search and you will be amazed at what turns up.

There are two types of mycorrhizae - ectomycorrhizae and endomycorrhizae.

Ectomycorrhizae colonize the outsides of the root cells and are most typically found in northern coniferous forest such as pines, firs and spruces, and hardwood forests such as oak, beech and birch. Here in south Florida oak and pine are the two most common ectomycorrhizal trees. The fruiting bodies of these fungi are born above ground in what we know as puffballs or mushrooms and the spores of the eclomycorrhizae are wind disseminated.

Endomycorrhizae colonize on the inside of the cell walls and spores are found below ground and not wind disseminated. The most common endomycorrhizae are vesicular-arbuscular mycorrhizae (VAM), and are associated with mangoes, citrus, mahogany, avocados, and in general, except for oak and pine trees, all of the remaining landscape and vegetable plants grown in South Florida except members of the cabbage family.

Both types of mycorrhizae produce an extensive web-like growth called hyphae outside of the root. Mycorrhizal fungi develop an immense network of hyphae that, in effect, serve as extensions of the plant root system. Because the surface area of the hyphae may be several hundred times the surface area of the roots, plants have access to a much larger volume of soil, and thus water and nutrients, than they would through their roots alone. By sending threads of hyphae far from the normal root zone, mycorrhizal fungi also improve the soil structure, thus improving the porosity of the soil.

Mycorrhizae, like beneficial soil bacteria, are not a panacea; they only help “mother nature” do what she does best, i.e. grow better plants. One of the more interesting facts about inoculating your soil with mycorrhizae is that it only has to be done once. After the initial inoculation the mycorrhizae will continue to grow with the root system and in time even inoculate other plants.

So, what can you do to add mycorrhizae to your soil. The process is simple; at the time of planting just mix the mycorrhizae with the back fill; in the case of potted plants use a pencil as a dowel to punch 2 to 4 holes, 3 to 4 inches deep in a pot, then add 1 tablespoon of material to each hole. In existing landscapes, set up a grid 30 inches on center, then with a broom handle punch holes 10 inches deep, put 1/4 cup of mycorrhizae in each hole then fill the hole with soil.