What is wrong with my citrus trees?

I have 4-year old Meyer Lemon and Mexican Lime trees that I planted one year ago. They came from Walter Andersen Nursery, so a respectable source, and have been planted in one of our typical sandy/loamy San Diego canyon hillsides. They are on a drip irrigation system and get watered deep and long every ~1 week or so, depending on the heat that week.

I am at a loss, we’ve tried what seems like everything: fertilizing, trace minerals, pest control, … Any idea from the experts out there?

Additional Picture:

They do largely defoliate during winter, but I’d expect them to have rebounded by now. Did you check the soil to make sure it isn’t riddled with gopher tunnels and that water was spreading throughout the root zone. Sometimes a single emitter just keeps a very small circle wet, even without tunneling destroying root contact.

When I lived in CA and trees stopped growing I’d create a bowl with soil and fill it up with water while tamping down the soil with my bare feet. Gophers were a constant, and even if they didn’t like the roots of a plant they could retard growth.

Inground citrus don,t need that much water. Fertilizer is out of reach, drained down the hill quickly. Just mulch it.

Citrus may not need much water in Florida but this is southern CA. It can go 6-9 months with no rain. Looks awfully dry to me. I’d try wetting a bigger area. Do I think that’s the only issue, probably not. But nothing else is obvious from afar.

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Watering once a week deeply is good practice but for a well established tree. Young trees need more frequent watering, especially in dry and hot SoCal. You slso need to mulch to preserve moisture. And pile on some compost too.

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When did this start happening? I once over fertilized a citrus tree and it ended up looking like that but then recovered. It definitely took a while.

Thank you all for the replies! Let me try to answer the questions in order:

  • Single Emitter - I have two of them, about a foot apart. One by the stem (intended for what was in the pot when I got them) and one uphill of the tree.
  • Gophers - I’ve been on top of the gophers and gleefully keep tally on my kill board. I should do a dedicated check on these trees though.
  • Amount of Water - We had a fairly wet winter, and I watered them twice a week last year, ~2gals each time (So for gals total). I finally got a soil moisture reader this month and am waiting for the soil (~8in down) to change from “moist” to just dry before watering again. We have pockets of loam/clay around here, so I wonder whether “wet feet” was part of the issue (hence the moisture reader).
  • Fertilizer - Applied liquid fertilizer it on April 1st. Likely hadn’t given them enough before that, but I would have thought to see changes by now.
  • Mulch/Compost - Agree with that one. Waiting for the local greenery to open up again

It’s kind of been like that starting early summer last year. Leaves started yellowing (no particular pattern, just slowly turning yellow) and then fell off. And never really came back… I like the idea of piling a large amount of compost and mulch around them though. Definitely won’t hurt…

So have you run a hose and water didn’t quickly disappear through tunnels underground, or at least you’ve stood on the soil to make sure it is firm around the roots? Also, have you have gotten your hands in the soil and made sure the water is spreading out over the entire root area?

Is it painted white?

alan - just went and verified, and we’re clear of gophers and ground is firm around the roots.

Just to make sure I understand your second question though: Do you mean digging down near the dripper/root ball? Usually, after I irrigate, the “bowl of dirt” around the trunk is we at the surface, but I haven’t dug down. I’ll check on that tomorrow as I think the irrigation will run tonight.

Yes - I painted it white after it started loosing its leaves in an effort to prevent sunburn. I used water-based latex paint.

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The moment I see my trees struggling, I stop depending on any drip irrigation. Stick a screwdriver into the soil. Does it come up with wet soil?

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The thing about container grown trees is when they are transplanted they can dry out in hot, low humidity weather in a few hours. To achieve drainage in a pot, potting “soil” has to be very coarse so not only does it hold very little water, but the soil around it will suck the water from it when that soil becomes dry through capillary pull (coarse to finer textures). Also, if you cover the potting soil with any real soil when transplanting, water tends to run around it, so you have to be sure the top of the potting soil is even or slightly above the true soil to be assured water is reaching the potting soil before the tree establishes roots in the real soil. If roots are dried out during establishment, trees can be permanently stunted.

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Alan and bleedingdirt - I’m learning all kinds of good stuff here. There is compacted dirt stuck on the screwdriver, but its more compacted than it is wet. So it sounds like we’re closing in on them having possibly not enough water (amount)? Or not frequently enough?

How do I make sure I don’t give them “wet feet” from overwatering? Would that only happen if you had standing water?

Using a decent moisture meter may help.bb

I have this one - would you recommend a different one?

I recently bought the very same one and don’t like it.The one that @ramv has,that is moisture only,is better.He should see this post and give more info.bb

I use this one
https://www.amazon.com/REOTEMP-Garden-Compost-Moisture-Testing/dp/B01L7PAEM0/ref=sr_1_29?dchild=1&keywords=soil+moisture+meter&qid=1589147265&sr=8-29

Responds fast. Definitely recommend it.

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I have this tree in my yard here in NorCal, it never defoliates in the winter. It’ll stop putting out growth, but doesn’t drop the leaves like the OP’s tree.

My guess is more slow release fertilizing is required. If you have nutrient deficient soil the liquid stuff doesn’t cut it imho. Also, I would mulch at least 2-3" deep to keep moisture from escaping. It certainly doesn’t look overwatered as the remaining leaves have good color.