Advice from the Help Desk of the
UC Master Gardener Program of Contra Costa County
Client: I wondering if you could help identify the issue with some of the leaves on my Lisbon lemon tree? I typically water once a week and not again until it dries out.
MGCC Help Desk Response: Thank you for contacting the UC Master Gardener Program Help Desk with your question about your lemon tree. Thank you for the photograph which was very helpful.
The vein yellowing evident in the photograph you sent could be due to several factors:
- There is a virus that can cause vein yellowing, but it is not common in our area, and so is probably not the cause.
- Herbicide toxicity can cause this type of symptom. If you have used an herbicide containing either diuron or bromacil, that could be the cause. If you have not used herbicides, then the cause is probably nitrogen deficiency.
- Although nitrogen deficiency symptoms usually present as more general yellowing rather than prominent vein yellowing, nitrogen deficiency can cause vein yellowing when the soil is cold (usually during the winter months), or if stems or the trunk are girdled (mechanically constricted). If there are any ties around your tree, you should remove them.
Lemon trees need regular fertilization, particularly with nitrogen, to remain healthy and productive. If you have not fertilized your tree this spring, we recommend that you do so now. You can either use ammonium sulfate or a standard citrus fertilizer. Information on proper nitrogen fertilization of citrus, based on the age of the tree, can be found at this University of California website http://ipm.ucdavis.edu/PMG/GARDEN/FRUIT/CULTURAL/citfertilization.html.Or you can just follow the directions on the fertilizer label.
Citrus has many roots near the soil surface. Lemon tree roots should not be disturbed by digging or cultivating, since damaged roots will negatively impact water and nutrient absorption. At least several inches of mulch under the entire tree is usually also recommended to protect the roots, keep the roots cool, retain Irrigation moisture, and minimize competing weeds. Keep the mulch at least 6” from the trunk.
Citrus should be watered every 7 - 10 days during the dry season. Additional information on how to water citrus can be found (and/or downloaded free) at the University of California's website http://ipm.ucdavis.edu/PMG/GARDEN/FRUIT/CULTURAL/citruswatering.html .
I hope that this information is helpful. If you water and fertilize the lemon tree properly but the leaves do not green up with 4 weeks, please feel free to contact us again.
Help Desk of the UC Master Gardener Program of Contra Costa County (JL)
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: email@example.com, 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 (http://ucanr.edu/blogs/CCMGBlog/).
Help for the Gardener from the
Contra Costa Master Gardeners' Help Desk
Description of Client's Question:
A client wrote in saying that he had read some advice about using coffee grounds as a fertilizer. The advice apparently also noted that coffee grounds would be a deterrent to gophers and moles. About two years ago, the client applied about 500 pounds of coffee grounds in a small area, but stopped when his lawn and some native plants started to die. (But the client did note that the coffee grounds got rid of the gophers!).
The client said that even after he ceased using coffee grounds, the plants have not recovered and the lawn still looks dead. He thought that perhaps the soil had become too acidic and perhaps gypsum could be added to remedy the problem.
Here's the advice that Master Gardeners gave the client:
Soil acidity isn't the reason why nothing is able to grow in the areas where you applied coffee grounds, nitrogen depletion is. In fact, coffee grounds don't cause soils to become acidic. The acidity in coffee is water soluble and the acidity in the beans ends up in the coffee when the ground beans are brewed.
Oregon State University recently conducted a study on garden use of coffee grounds (http://extension.oregonstate.edu/lane/sites/default/files/documents/cffee07.pdf ). OSU found that large amounts of coffee grounds stimulate the development of soil microorganisms which in turn use the nitrogen in your soil to process the coffee grounds. The study also states that acidity of the resulting soil is not the major issue, but nitrogen depletion of the soil is a major concern.
I would try using a good organic nitrogen fertilizer and applying it to the area where growth has ceased. The organic fertilizers are slow release and will not burn your lawn or surrounding plants. It may take repeated applications over time to adjust the soil composition. If you have bare ground that is affected, you could also try covering the area with compost or leaves and let the natural composting process help to balance your soil.
Editor's Note: Each month the CCMG Help Desk's Quality Assurance Team selects responses to county residents' Help Desk questions that produced informative responses that are either unique or unusual, or provided updated information that would be informative to all gardeners, or are of general interest, especially of seasonal concerns. We are highlighting these responses in the HortCOCO blog so all interested Master Gardeners and the public may utilize the information.
The CCMG Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday 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: firstname.lastname@example.org, and we are on the web at http://ccmg.ucanr.edu/