Q: I have a lime bush in a pot on my porch that looks great, but it doesn’t have many fruits on it. What can I do to make it produce? — June, Cayucos
A: There are plenty of things you can do to increase the yield and the health of your container lime and other citrus plants and trees. Besides providing the basics — maximum sunlight, protection from winds and well-drained soil — focus on giving your plants proper nutrients (fertilizer).
Young citrus trees and container plants have similar needs. Their major requirement is nitrogen. Find a nitrogen fertilizer such as urea or ammonium nitrate. Determine the needs of your plant and follow the label instructions.
According to the UC IPM website, trees in containers may require less fertilizer than full size trees planted in the ground. The suggested application rate for the first year of full size trees is one tablespoon of nitrogen fertilizer, three times per year per tree.
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Slow-release fertilizers may help to avoid overfertilizing your container citrus, and will supply the necessary nutrients over a longer period of time. As the tree matures, the application rate is increased about a tenth of a pound every year up to the fifth year. Fully grown five-year-old trees, about 15 to 20 feet tall, need 1 pound of nitrogen per year.
Remember to calculate the amount of actual nitrogen being applied. Materials such as ammonium nitrate typically carry only 3 percent nitrogen. Applying the nitrogen in late winter (prior to bloom) and early spring will help the trees produce flowers and quality fruit. Apply the fertilizer in the root zone beneath the canopy. Avoid fertilizing during summer and fall as it may delay fruit coloring and affect fruit quality.
Other than nitrogen, citrus plants need iron, zinc, magnesium, phosphorous and boron, most of which are sufficiently available in the soil. Commercial fertilizers contain small elements of these nutrients, so be sure of your plants’ actual needs to save time, money and to avoid leaching of excess nutrients that your plant did not need.
Talk with your friendly Master Gardener if you have any specific problems. In the meantime, enjoy your tasty fresh squeezed orange juice, lemonade or lime spritzer as you take a break from gardening.
GOT A GARDENING QUESTION?
Contact the University of California Cooperative Extension Master Gardeners: at 781-5939 from 1 to 5 p.m. on Monday and Thursday; at 473-7190 from 10 a.m. to noon on Wednesday in Arroyo Grande; and at 434-4105 from 9 a.m. to noon on Wednesday in Templeton. Visit the UCCE Master Gardeners website at http://ucanr.org/sites/mgslo or email firstname.lastname@example.org .