Your citrus trees are hungry

The sun is beating down in the Phoenix area and I am getting into the garden at sunrise to avoid the incessant heat from the temperature and the sun’s strength as it rises in the sky. It’s 107 degrees today and I get both sun and heatstroke easily, which isn’t a good combination for a gardener! This heat also triggers a reminder to water our gardens more frequently. It’s feeling the same way you might as you walk into the heat blast. Another item on my list is to fertilize the tangelo and lemon trees in my backyard.

It was a rough year for some of you with your citrus. Some people reported that their citrus was small in size and others said the fruit was dry. Other gardeners said they had an unusual amount of fruit drop. Our strange climate in the Southwest last year played a part in that and this year hasn’t promised to be any better with the warm then cold temperature changes in February through April, followed by strong winds during blossom time. We are experiencing a major climate change and it doesn’t look like it will correct itself, so we have to adapt to it and take better care of our trees to help them through the climate fluctuation.

CHANGE YOUR WATERING SCHEDULE

Right now (in May), we are experiencing triple-digit temperatures in the low desert. That means it’s time to change your watering schedule if you haven’t done so already (see the chart to the right). Don’t change the amount of time you water your fruit trees for each watering because you still want to water to a depth of about three feet, but water more frequently. Attached is an irrigation schedule for different times of the year. If you were watering every two weeks, switch to approximately every week. You should also shift watering to evening or early morning so that the roots are cool going into the day and the evaporation is kept to a minimum.

It’s also a good time to check that your water is still going down to three feet. You will do this by using a soil probe or simply a long rebar rod at least three feet long. An hour or two after you water, push the rod into the ground close to one of the drip emitters. It will stop at the point it hits dry ground. If the rod went in at least 2.5 feet, you are fine. If it goes deeper than three feet, you are applying too much water per watering day. Some arborists will argue that the bulk of the roots are in the first 18 inches, and that may be true. But in the Southwest, we want to encourage deep root growth both to sustain our trees for longer periods of time between watering and to develop stronger trees that can withstand those early spring and monsoon winds. If the depth of the water saturation is less than it used to be, check the drip lines to make sure that some aren’t clogged or that you don’t have leaks.

One of the most important things you can do for all of your fruit trees is move your drip line out as your tree grows. The drip emitters should be around the outer edge of your tree canopy. Your youngest roots are reaching that far and they are the ones that take in the most water and nutrients. When your tree was planted, you or the landscaper probably put the drip line near the trunk. For the first six months, that is a good place for them so the newly planted root ball gets plenty of water to encourage root growth. After about six months, the roots grow beyond the root ball and the drip emitters need to be moved further out to the edge of the tree canopy.

When I plant a tree, I use extra spaghetti line (that long thin black water line with the drip emitter at the end) for the lines that will need to reach further away from the main irrigation line as the tree grows. Then I wrap it to shorten it and bury it a bit to protect it. I can then release more line as the tree grows. Some people use drip extenders to lengthen the line when needed, but I find that the connectors will occasionally leak and I have to then dig up the main line to add a new emitter line and plug the hole of the old one.

FERTILIZE CITRUS TREES

It’s also time to fertilize your citrus. If you have planted the tree in the past year, skip fertilization for 12 months from planting. Citrus trees that have gone through one fruit cycle (one year from planting) should be fed three times a year. A general rule is to fertilize citrus around Valentine’s Day, Memorial Day and Labor Day. Dr. Glenn Wright, a citrus specialist from the University of Arizona, suggests a more customized fertilizing plan per type:

  • For oranges, tangerines and grapefruit: January/February, March/April and May/June.
  • For lemons and limes: January/February, March/April and August/September.

His graph is to the left, and I have attached his guide for citrus fertilization  that also includes instructions.

You can add separate nutrients, as shown in the second graph to the right, or you can simply buy a good balanced citrus fertilizer. The amount on the back of the bag shows how much a YEAR a tree is to receive. So, to feed it on the three dates, divide by the amount by three. Loosen the ground a few inches around the drip line/canopy edge completely around the tree, spread the fertilizer in the loosened trench you created, work it into the ground and water the area liberally and deeply.

Other fruit trees are fertilized just before they bud (January is best). I’ll spend some time on the topic as we approach that month. A great article on all fruit trees needs was written by Master Gardeners.

If you watch your watering frequency and fertilize three times a year, your citrus should be happy and handle the climate changes a bit better. Don’t forget to lessen watering frequency once we hit October!

Jknapp

I am a certified agriscape designer and Maricopa County Master Gardener. I have been gardening since I was six years old and worked in my grandfather's garden. I believe that the only way to be a responsible gardener is to garden organically. It improves our soil, is safer for us to eat, sustainable and it protects our pollinators and soil from chemical poisoning.