LANDSCAPING TIPS brought to you by the Arizona Landscape Contractors’ Association, the Sustainable Landscape Management (SLM) and the Arizona Certified Landscape Professional (ACLP) programs www.ALCA.org
Citrus in the Landscape
One of the famous five C's of Arizona is our lovely Citrus. While citrus used to be a much larger part of our state economy, it remains to be an important and valued part of our landscapes. If you already have citrus trees to maintain or are thinking of adding them to your landscape this spring (not yet - it's too cold!), it is good to know that some of the past accepted landscape practices for this group of tropical plants have been proven to be harmful to the trees and may hasten their decline. There are also updated fertilization guidelines that promote healthier growth. As in any industry, sometimes the past standards can take many years or even decades to be rejected and replaced by newer, proven, better practices.
Past practice: Prune the citrus tree into a "standard" or lollipop shape, and paint the trunk white.
Better practice: Allow newly planted trees to have a more natural shape with lower branches. Only prune dead and broken branches, and minimally to remove weak or crossing branches and for sprout removal.
Why? Citrus trees, being tropical plants not native to our desert, are susceptible to sunburn if the trunk is exposed by pruning into an unnatural shape. The white paint was used as a sunscreen. It is a better practice for the tree to retain some lower branches to shade the trunk naturally, and so the white paint will not be necessary. Also, leaving the lower branches has an added benefit to the tree by strengthening the trunk. Over-pruning stresses the trees, requiring more inputs of water, fertilizer and unnecessary trips to the landfill.
Past Practice: Fertilize all citrus on the same schedule, 3 times a year - around Valentine's Day, Memorial Day and Labor Day.
Better Practice: Use the updated Citrus Fertilization Chart for Arizona (Glenn Wright) Pub az1671-2015 from the Arizona Cooperative Extension.
https://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1671-2015.pdf
How? First, use the chart to find the annual fertilizer requirement depending on the size of the tree then, divide the requirement by thirds. This is where the guidelines change, depending on the type of tree. You will also notice that the window for fertilization is larger, which is helpful in case you think you may have missed your chance for a seasonal application.
Fertilize oranges, tangerines and grapefruit: 1/3 of their annual requirement in January-February, 1/3 in March-April and 1/3 in May-June - so none in the last half of the year!
Fertilize lemons and limes with 1/3 of their annual requirement in January-February, 1/3 in March-April and 1/3 in August-September.
Citrus uses more water and requires more maintenance than the desert-adapted plants but, as an established part of our landscape, it is in the best interest of sustainability to properly care for them to maximize their benefits to the landscape and minimize their use of resources.
