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Gardening: Friendly Fungi

Mushrooms Form Beneficial Bonds with Living Plants


What do chanterelles, truffles, porcini, and matsutaki mushrooms have in common? Since they are not photosynthetic, mushrooms must obtain their nutrients from some source other than the sun. Some fungi are decomposers; they utilize dead plant (and animal) sources to grow. Others, the ones just mentioned included, are symbionts that form associations with living plants, which serve as hosts providing them with nutrients. Many of this type of organism don’t just take; they also give — by forming bonds with trees and shrubs and helping them absorb hundreds of times more water than they would normally be able to do, they live in mutualistic associations that benefit both species.

The recognizable (and tasty) aerial structures are just their ephemeral reproductive parts. The largest percentage of the body of these fabulous fungi lives in the soil and is composed of fragile, nearly microscopic threads. The delicate and complex relationships between fungi and green plants make these gourmet treats difficult to grow commercially. It requires that subtle, yet essential, connection between host plant species and fungal mycelium to produce the perfect mushroom (and a healthy forest).

There are plenty of other fungi/green plant associations that humans don’t notice or enjoy for dinner, but they are a major key to healthy gardens. All of these beneficial organisms fall into a general category called mycorrhizae. Mycorrhizae act in association with the roots of plants to increase their water and nutrient uptake capabilities many-fold. Some research shows that the functional surface area of roots in symbiotic relationship with mycorrhizal fungi is increased by as much as 700 percent.

Not many of these beneficial organisms are available commercially, but some are, and it is quite easy to add beneficial species of fungi to garden soils to jump-start the process of enlisting their help in fostering healthy plants. With the help of this network of fungal threads (called hyphae), plants are able to maximize nutrient and water uptake and even survive periods of dryness more easily. It is quite possible to add mycorrhizae when renovating soil around existing plants and it is supremely simple to inoculate new plantings with these additives. The specific formulations will be different for each application, so read the labels and ask for help from the nursery or garden center personnel. The introduced fungal spores need to find active roots within 24-48 hours of germination, so they should be added just before planting or to established plants with intact roots.

What’s interesting about the research on these helpful microorganisms is that in follow-up testing of inoculated soil, the original (commercial) species have largely been replaced by species native to the plant and soil types. The general conclusion is that they paved the way for the native’s return. To encourage this happy success, be sure to avoid the use of chemical fertilizers and pesticides that degrade the soil foodweb. This will allow the remnant populations to regenerate. These fungi are also killed by the heating of compost and may not be present at all in degraded soils.

Once again, the simple rule that healthy soil means healthy plants has complex roots (pun intended).

Virginia Hayes, curator of Ganna Walska Lotusland, will answer your gardening questions. Address them to Gardens, The Independent, 122 W. Figueroa St., S.B., CA 93101. Send email to vahayes@lotusland.org.

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