Q: What are mycorrhizae and why are they important to trees?
– Stef, Boulder
A: Mycorrhizae are fungi that occur in a symbiotic relationship with woody plant roots. These organisms occur naturally and are found in soils vegetated with native forests. The high plains grasslands, where Denver is located, is an ecosystem that does not support a lot of native woody plants, so you won’t find many of these organisms here.
Mycorrhizae, however, are one of many microorganisms that must be present for proper growth and development of trees.
There are two main types of mycorrhizae: ecto-mycorrhizae and endo-mycorrhizae. Ecto-mycorrhizae join with pines, spruce, fir and oaks. Endo-mycorrhizae take to maples and other deciduous trees.
Mycorrhizae enable tree roots to take in a greater amount of nutrients and water. These fungi also help maintain soil structure, increase root mass and efficiency, reduce moisture stress, protect plants from detrimental effects of heavy metals and other potentially toxic substances, and protect roots from various diseases. Although mycorrhizae take carbohydrates and other compounds from the plant, their overall benefit is good.
Many tree-care companies use mycorrhizae spores in their nutrient programs. The spores are mixed into a liquid solution and injected into the soil under low pressure using a soil probe. Humic acids, beneficial bacteria spores, kelp extract, biostimulants, amino acids, vitamins and other materials often are included to improve the root-zone ecosystem.
Some prefer to use high-nitrogen fertilizers, but these promote rapid vegetative growth that may be weak and prone to insect infestation and diseases.
But attitudes within the arboricultural industry have been changing from “feeding” trees with high nitrogen to promoting a healthy soil ecosystem that will support healthy tree-root growth.
Robert Brudenell is a registered consulting arborist and owner of The Natural Way Inc. Send questions to Robert@thenaturalwayinc.net.
