Not having first-hand sight I would guess that you are getting a caterpillar invasion. Have you tried spraying the poor thing with Bt?

I haven't. I did spray it last year with Captain Jacks as this issue has been going on for years, that spray didn't make a difference. I do have little mini spiders on the tree but I do not see any caterpillar. I will try BT and keep my fingers crossed. Thanks for the advice.

Spiders or spider mites? Take some to your nursery and ask for identification and treatment.

Follow the watering suggestions above and check for spider mites. Witch's broom is a symptom of other problems and indicates the tree is stressed. It doesn't look like your tree has that.

Pests of Palo Verde

I tell people that the road to a green thumb is paved with the corpses of dead plants. I've killed more plants that you'll probably ever own. So don't feel too bad. Everyone has to start somewhere.

If the drippers are right next to the trunk, you'll want to move them away from it, probably about a foot away at least. Drippers should never be right next to the trunk. Irrigation needs to water an area not a tiny little patch next to a plant. This is because woody perennials like shrubs and trees have wide and shallow roots that only go down about 2 feet and extend out past the canopy about 3-4x. So a tree in a narrow planting strip is going to fill every square inches of that bed with roots. So if you only have a couple emitters near the trunk you will have to add more to cover the whole area.

If you don't want to use a drip system for the tree, you could just handwater once a week to start weening it off the shallow crown watering. After a month I would move to every two weeks. Here is the reference evapotranspiration chart for San Diego. The numbers are inches of water per month that is needed to grow fescue grass.

The tree wants moderate (50% ET0) amounts of water during the wet winter season and low (20% ET0) amounts of water during the dry summer season. Seeing as how 20% of 5.7 is only about 1-1/8" that is pretty easy to do by hand once a month if you can flood the bed. An inch of water is not going to 'saturate' the ground btw.

In order to ID spider mites you are going to need a 10x magnifying glass or loupe at minimum. 30x will make it a lot easier to see the mites. Loupes can be picked up cheap on Amazon.

Bayer 3 in 1 is a miticide that is a lot safer for your plants than neem. I never use neem anymore, too many bad experiences.

The only fertilizer you should use without a soil test is shredded wood mulch. You need to send a soil sample to UMass for testing before I can recommend a fertilization schedule.

https://ag.umass.edu/services/soil-plant-nutrient-testing-laboratory

You should put the water somewhere between edge of the canopy and halfway between the edge and the trunk. You can chain multiple emitters together to make a big circle and then water the way Nil13 recommends. You do not want to dribble water into the area several times per week. I only water one of my trees and I use a soaker hose which I hook up to a hose monthly during the hot months. Your Palo Verde should be able to tolerate no supplemental water in a few years although it may lose its leaves in the summer.

Think about where these trees come from - desert conditions. The rain there is violent and infrequent, analogous to a huge drenching and then drying out. I water my PVs overhead for 30-45 minutes roughly every two weeks in summer. I planted them on mounds in very gravelly soil as they do not want to be wet and cold at the same time, an issue in my NoCA zone 9b in winter. Drip is great for water conservation and weed suppression but it does not resemble anything that occurs in nature. As Gilda Radnor said 'It's always something!'

Also wonder if you have sufficient heat for 'Desert Museum' being 10 minutes from the ocean in mild San Diego. Have you seen healthy ones in your immediate area? Mildew might be inevitable in that location.

There are some PV in my neighborhood, close to the water in northern SD county. They don't bloom quite as exuberantly as in Arizona, but they're still attractive trees. Temple Solel, just to the east of 5 in Encinitas has beautiful PVs in their parking lot.

Remember parking lots, especially asphalt ones, produce a pretty serious heat island effect.

Honestly, there aren't too many PV close to us, maybe for this reason. Husband corrected me and we live 4 miles from the beach which doesn't help our case. After listening to all of you wise folks, we changed our watering routine and I bought some stuff to help with the spider mites. Next month I have someone coming by to prune them slightly and I hope all of this helps. If you haven't figured it out, I am an all or nothing gal. I'm taking all of your advice and putting it to work. I will have to report on the progress made. The way these two trees are planted, they get a lot of sun and I anticipate they will never have as many flowers as trees in the east but I at least hope for some leaves and less webs. Positive thoughts.

Pruning in the heat of summer is a bad idea. Wait until you see new growth in the Fall to prune. Pruning in summer will force new growth when it should be going dormant.

Hi Christie, I have some suggestions for you.. First I'd like to recommend you get a good reference book on California native plants. One that I like a lot, and is good for beginners, is "Care & Maintenance of Southern California Native Plant Gardens" by Bart O'Brien, Betsey Landis, and Ellen Mackey, 2006. I bought mine at my local botanic garden, RSABG, for $15.

Moosa Creek Nursery, a wonderful CA native plant nursery, has an excellent and very informative website. Here is their page on Desert Museum, palo verde: Desert Museum
And a quote from that page, " Like its parent
plants, ‘Desert Museum’ loves blazing full sun and is impervious to
heat; it can take wind, poor soil and temperatures down to 15 degrees
Fahrenheit. It is a trouble free, fast growing tree and can reach its
full height in as little as 3 to 5 years. Once established, needs only
occasional watering at the most, and none in many circumstances." Yours isn't used to getting watered like this yet and needs to be transitioned gradually.

Another suggestion I have if you are interested in a small trip, is to come to the Rancho Santa Ana Botanic Garden, in Claremont (next to Pomona) for a class being held there on July 11 called "Intro to Irrigation for Native Plants". Here's the link, Irrigation for Native Plants
And the details,

"Wednesday

Jul

11

6 pm - 8 pm

How
much and how often? Sprinkle
or drip? Which emitters are best? What to look for in a control panel?
Can I modify my sprinklers designed for lawn to devise a new system that
will work well for natives? How to troubleshoot an older system. What
about my oak tree? These are some of the topics that RSABG Director of
Horticulture Peter Evans will go over in a two-hour class on Irrigation
for Natives." (there is a registration fee, see site for that)

I have three plants of Desert Museum that I bought at RSABG in 2011. They are now big and well-established. They start blooming when the weather warms up in spring and flower off and on until winter. I just deep watered all three of them about two weeks ago. I might deep water them once this summer--or not. They will be fine without any summer water, but my plants are used to this. I have never fertilized any of them.

Here are some photos I took on May 8:

Melissa

If you don't mind a drive, come to the Garden Expo at South Coast Research and Extension Center in Irvine, Ca. on Sept. 29th . Garden Expo

Below is a photo of part of the demonstration garden where you can see a Palo Verde and other drought tolerant plants. There will also be informational booths, lectures, and a plant sale.

I was always told that Desert Museum is not a good choice for coastal California. It probably has a hard time dealing with nighttime moisture from coastal fog and prefers hot weather.

I live in Torrey Hills, just west of the I5 and Del Mar. Our palo verde has never done well, always has mildewed leaves and never blooms. Forget trying to grow this too close to the coast. I am pulling it out and putting in something that likes it here.

SPRAY WITH WHOLE MILK! i kid you not....our poor tree was plagued with powdery mildew for the year we've had it and pithing one week....all new beautiful green growth everywhere

I believe the climate of the desert SW where the palo verde does best is dry w/ distinct 2 rainy seasons: a wet winter and an even wetter summer in the form of thundering monsoonal rain as seen in AZ. In coastaal CA our summer is dry and our winter is very wet w/ high moisture. The seasonality of the rain sets the growth cycle. Without it the tree stalls.

Hi the same exact thing happened to our Pv. We were so fed up as it didn’t flower at all. It’s so heavy under the spider web of some sort. What have worked for us was blowing the tree with the leaf blower. It was like a miracle. The tree lost some leaves as well but now a week later it already grew new ones and looked greener and taller. I wish we knew this before.

Now it’s so much bigger and teller and healthy. Will be blowing again soon.

wow, good to know. I was doing the same thing with water but don't like to waste. leaf blower, who would have thought. so far with so much sun, more consistent watering and fertilizer, we have had the best year yet but still random webs. thanks for the suggestion

Hi there!  I live in the San Diego State University area, and my Desert Museum is doing the exact same thing!   Weve had a ton of rain since December and my DM looks dry.  Curious what yours is looking line these days?

we abandoned ours after watching it struggle for 2 years, pulled it out and planted something else. It is a desert plant, and coastal humidity without big heat just doesn't meet its needs.

San Diego county can have coastal fog, 70 degree heat inland in El Cajon, and snow in the mountains of Julian in the same day - it's not all surfboards coastal air.  I live inland on the border of San Diego City proper, and La Mesa, and there are plenty of DM's thriving in my neighborhood, just not mine.

I live in San Diego about 10 minures inland, too too, and i am experiencing the EXACT same problem!! Did you find a solution?

I havent received a response from the original poster.  I decided to reach out to the free helpline with Master Gardeners Association in San Diego and I'm waiting for a response.  Here is their website mastergardenersd.org/solve-a-problem/

Thanks for the reply! ill check out the link provided. appreci appreciate your help!

Noting the same issue with my PV in Cardiff, east of the 5. Spraying with water seems to work, but also seems temporary and wasteful. Looking like i need to pull. :(

I found that spraying mine with the highest pressure setting to ”clean” the tree helped remove any mites/dusty looking stuff and cutting back to less frequent, deeper waterings have helped but still not great. we pulled one of the three trees. one tree is doing better than the the other remaining—so odd since both came from moon valley nursery—not sure why one is doing better than the other but we are going to keep them and hope they keep growing. they are two years old.

This thread has been so so helpful! We had this issue and I thought this was witches broom but good to know it might be mites. I'm in escondido so it's plenty hot - definitely we were overwatering with drip.

So happy I found this thread! Excited to spray out my PV and use the neem oil. Thank you all for the info. Super helpful!

My DM is happy right now. I had lots of conflicting feedback from the San Diego Master Gardener - some said not watering deeply enough, others said watering too much. I hosed out my tree, several times last year and noticed lots of worms that would suddenly descend from the branches, and white moths fly away. I just religiously sprayed the tree weekly with water, even using some bug spray on the worms (I was afraid to use neem or systemic). Eventually the worms were gone, and my tree seems extra happy this year. I'm glad I was patient.

Oh, forgot to mention, last year I noticed several praying mantises on my tree, so they were feasting on something. I'm really glad I only sprayed the worms directly when I saw them if I had sprayed the whole tree, I would have killed them. I'm wondering if the PM's were another reason why my tree looks happy this year.

Hi all, referring back to this post (regarding the application of neem oil):

Nil13 usda:10a sunset:21 LA,CA (Mount Wash.)

Bayer 3 in 1 is a miticide that is a lot safer for your plants than neem. I never use neem anymore, too many bad experiences

I’m in Simi Valley with a beloved Desert Museum in the backyard. I had a couple of years of caterpillar infestation and sprayed the tree with jets of water. Last year the caterpillars didn’t return but the tree still seemed a bit stressed and did not have a good bloom. This year (2024) it had renewed itself with beautiful lush green leaves and I’ve been hopeful … but now the leaves have faded to a pale gray and are becoming brittle to the touch. I’m expecting them to drop.

I’m so sad because this is how the tree has looked in the past!