Advice for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County
Client's Request: I went on Tuesday evening to a very good presentation at the Lafayette Library by Master Gardeners. I had a question that the presenters could not answer and their advice was to ask it directly to the Help Desk -- so, here it is....
I have planted a new garden with native plants and have not added any amendment to support the plants' growth. I read online that mycorrhizal fungi can be added after the plant has been set in the ground and it will enable healthier root and plan growth. Is that correct?
Help Desk Response: Thank you for contacting the UC Master Gardener program regarding mycorrhizal fungi and your native garden. We know that plants and mycorrhizal fungi live in a symbiotic relationship, very beneficial to both species. The fungi colonize the plant roots, helping with uptake of water and minerals. It is well known that plants in healthy soils with good mycorrhizal colonization are much healthier. You can promote this by appropriate irrigation, minimizing soil disturbance by not tilling, and limiting fertilizer, especially phosphorus. Also, using a surface mulch will help.
There have been many studies on the effects of mycorrhizae on growing plants, which show definite benefits, but it is not clear that adding them to an existing landscape is helpful. There are many different species of mycorrhizae, and it seems that they need to be adapted to the particular environment or plant species, and if you add 'foreign' ones, those native fungi already present may defend their territory and your garden will receive little or no benefit. Also, one study that I know of looked at viability of commercially available mycorrhizae inoculants and found that some did not have any live ones! That being said, if you still want to try this, a reputable and appropriate source should be used.
If your garden was prepared appropriately, and the plants are healthy and thriving, and you are using mulch, it should be fine without adding the mycorrhizae. In addition, I could not find any recommendation to add mycorrhizae for this situation on the California Native Plant Society website: http://www.cnps.org/cnps/grownative/getstarted/starting_a_garden.php
I hope this has been helpful and that your garden will thrive. If you have further questions, please feel free to contact us again.
Help Desk of the UC Master Gardener Program of Contra Costa County (SMW)
Note: The UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. We can also be reached via telephone: (925)646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog (//ucanr.edu/blogs/CCMGBlog/)