I'm in Sonoma County and have dozens of these (two long hedges), assuming you mean Dodonea viscosa. Pruning will not hurt these plants at all - you can hack away, shear, standardize, espalier, etc at will. They are pretty bullet proof here, with the exception of frost damage, which is rare here and I would think unknown where you are, and not keeping them irrigated as they are getting established, when they indeed, dry up and die. I irrigate them in the summer as I find that they (like so many 'drought tolerant' plants) do better with a bit of water. Is there any chance that yours were receiving summer irrigation that suddenly stopped? That could account for it, but why just the four and not all? Sunset says that they can take regular water, fyi. Other thing to check is gophers if you have them there. Usually they leave enough soil disturbance so that they are immediately suspect, but not always. If possible you could dig one up and see what the roots look like.

Just wondering about your posts. I have some dodoneas that are about 6 years old. They got really big and I cut them back hard last year. Three (of the four) died. I really like them, so I bought some new plants, but I also think that the hard pruning killed them. I do irrigate them in summer, as it is really hot and dry here (Walnut Creek), and last year the deer ate them for the first time, but I was surprised that 3 of them did not make them through the winter. I think that I pruned them too hard and I will be more careful from now on.

I have pruned like crazy on some and had no problems. They can be standardized and sheared and per Sunset they can be espaliered and trained into a small tree. Neither the East Bay MUD book on plants for dry summers or the Am Hort pruning and training book mention any problems with pruning them; both suggest similar treatment - ok for hedging, shaping, etc etc. (Am Hort sez late summer or early spring for pruning). They are frost tender - really don't want to go below 32 for more than a brief period - you should be ok in zone 15, but if you had a hard freeze that could have done the second batch in, especially if they didn't get enough water. I think that the 'secret' to these is that people think that they are drought tolerant and then don't water them and they really need some summer water. The biggest ones that I have ever seen are at SFBG, despite their being native to Arizona and Hawaii and thus suggesting hot climates.

a hedge should never be one kind of anything ... ken

Gonna have to disagree with you on that one, Ken. To me-and I know I'm not alone here-a hedge is almost by definition a monotypical, linear, and very often sheared planting, intended to screen and to have a formal appearance. Now if you're talking shrub border, then yes, by all means, vary things up, use different elements. But in my world, hedges are exactly that-single species plantings. They exist in this form all over the world.

+oM

After two years of Arizona pines just dying we changed them all for purple hopseed, eight in all. Had them Professionally planted, as were the previous plants. This was back on May 11, 2017. Now we find that the hopseed are also dying, some barely hanging on. The ground was prepared for excess salt and for grubs, again by the plant company. The plants were healthy when planted and we irrigate them via soakers daily. Is there a way that they could be getting overwatered??? We live in the Arizona desert so it's really hot.

dig a few small holes.. in and around the plants ... AND FIND OUT HOW MUCH MOISTURE IS IN THE SOIL ... that is how you find out .. not by asking us ... adjust watering protocol appropriately ...

also talk to your installer ... they should still be under warranty ...

see link for general planting info ... not specific to AZ.. but interesting enough for you to talk with your seller on an informed basis ...

you probably should have started your own post.. and included some pix ... welcome to the forums.....

ken

https://sites.google.com/site/tnarboretum/Home/planting-a-tree-or-shrub

Replying to Cynthia, I do think that yes maybe you are overwatering. Even in Arizona I don't believe Hopseeds need water very day. It is interesting because mine that died (i'm the original poster) were in a semi shaded area, and the neighbors next door, on the other side of the fence where they were growing, i discovered were watering so much that it was soaking up and destroying the block wall there. I think now that overwatering is what killed them.

Thank you for your answer. We have cut the watering down and perhaps we might save some. We will wait and see. New to Arizona gardening and the heat. Much different in SoCal and Michigan.

I have had Purple Hopseed Bushes for about a year now. They are planted as a screen at our house in coastal SoCal. I had the same problem as some folks on here so I'm posting in case my story helps someone else. We had a happy little bush that had been growing for about 8 months, suddenly drop all its leaves and start to shrivel up. Despite all my efforts to figure out what was wrong, it kept declining and eventually we pulled it out. About a month later, the bushes growing to either side of that plant also started to lose their leaves. This time, I reacted much earlier and combed through each branch to look for the cause. I immediately found small, hard bumps saturated at the base of the bush and in clumps along the branches to about halfway up the bush. I had a bottle of Bayer Advanced 3-in-1 from a battle to save an Olive a few years back. The arborist we brought out to advise on the Olive told me about the Bayer concentrate, said I could get it at Home Depot and that it was a wide spectrum insecticide/fungicide. I went to work during non-bee hours (it is harmful to bees) and kept the spray directly on the branches and base. Scale matures in cycles so you have to spray at least 3 times, 1 to 2 weeks apart. After 3 sprays, they were all dead. I trimmed the base of the bushes so I could easily see if the scale was attempting a comeback and pruned the body to let more air and sun in (they don't like warmth or light). All are looking happy, healthy, bushy and are back to growing taller. Hope this helps!

It's true scale is a horrible problem with these guys, at least in So Cal. So gross! Glad you were able to save a couple of them!! I ended up planting all new ones, they all died.

It's been a few years that this problem started so I will finish the story by saying I am giving up on hopseeds. All of the new ones I planted thrived for (hmmm interesting) 8 years again and now they are one by one starting to die. No overwatering is happening, no scale, no trimming. All about 10 feet tall. I just pulled out the second one and I've got 5 left that are alive, but it's starting in on one. Very mysterious, very sad. But I need a screen more than anything now as our jerk neighbors built a second story. Hello Carolina Cherry Laurel!

i just pulled mine out today, died over the last few months, the other one about 5 feet apart is beautiful green, its summer here in the central valley with temperatures in the hundreds, no hard pruning no over watering, all the other landscape plants are doing great???

Mine started to dry up and looked stressed. I noticed a lot of ants, put down ant poison and problem solved. Plants look great now