Any herbicides used in the area?

tj

If you're in my part of the Bay area, it really could be herbicide. Many of my neighbors may drive electric cars and only eat organic, but they don't know or care what their gardeners use in their yards. :/

We've also had some light frost lately, depending on where you are. I don't know what frost damage would look like on these plants but it's something to consider.

I forbid roundup use in my own garden, and I am not near any major agricultural that would spray large quantities of herbicide. The damage on some of these plants was there in late Summer, so it is not a frost issue.

I think this situation may also be a lessen for me in why you should always sanitize garden shears between different plants. I strongly suspect that I have created this situation by never cleaning shears and then using them widely in the garden between different plants without cleaning.

What is the easiest way to sanitize shears without it becoming a giant hassle to keep spraying them and wiping as you switch from one plant to another?

A pint container with a 10% chlorox solution where you dip clippers for 30seconds between plants is relatively easy.

A final consideration to choosing a disinfectant treatment is how damaging it may be to your tools.
Teviotdale et al. (1991), who performed the most comprehensive study, found Lysol to be least corrosive
and Clorox to be the most harmful to pruning tools

https://s3.wp.wsu.edu/uploads/sites/403/2015/03/Pruning.pdf

@Embothrium so use spray-on Lysol in a can?

@gardengal48 Phytophthora looks like a good diagnosis. How does that disease spread?

It looks like Phytophthora is perfectly suited for this California clay soil we have that just fails to drain well during periods of high moisture. My hedges are on a very slight slope, so the water is draining right down through the affected plants. I basically have a drainage highway for the organisms to spread.

Does Phytophthora also attack Red Robin? The kind of drought stricken appearance the Red Robins have sound consistent with that condition. This could be in addition to the other Photinia disease that you cite.

How can I get a positive diagnosis for Phytophthora? Is there any way to get some soil samples tested, or do I need to find affected roots and look for tell tale signs of rot?

Some websites recommend a topical spray of the fungicide fosetyl-al (Aliette), hoping that this will move down into the roots. Do you think that has any merit?

Should I be removing any surface level sprayers and instead giving all of the water by drip irrigation? Should I be using minimum water and allowing the plants to live on the edge of insufficient watering? I was thinking of adding two or three inches of bark mulch around these hedges, hoping to provide them some nitrogen and also condition the soil. Now that looks like a bad idea because it might increase moisture and humidity around the roots?

If I plant hedges on a new property in the future, I am going to always use raised beds that give very good drainage. I have never had anything but problems with clay soil, except for very old and established plants that somehow got past the susceptible first decade and established a vast network of roots. Losing the existing hedges will be devastating to my garden. There isn't enough time left to start again from scratch. I will probably sell the home before I ever see a result from that.

@gardengal48 Regarding the azaleas, those are planted in bark with turface, a mixture that has been remarkable for growing my rhododendrons. The pots are on an automatic drip timer and during the summer I test the moisture and keep the flow rate and duration to a place that does not leave the soil saturated. The pots are well-draining. The pots might be a bit small.

I suspect the problem could be the lack of fertilizer. I will try to get them fertilized soon with an appropriate container fertilizer for azaleas.

How should I treat the lacebugs?

westes I have adobe soil and generally plant in large mounds of amended soil (with a generous amount of 1/4" lava pebbles added - sometimes up to 50%). The tree roots eventually make their way into the native soil, but they get established in much friendlier conditions.

Phytophthora is present in the soil. Some species are more susceptible than others but the key is really to make sure that your plants aren't stressed for other reasons.

Certain rhododendrons are relatively tolerant of pH over 7. So for the azaleas, do check the pH of the container medium AND the pH of the irrigation water. You may be able to get the pH of the water from the water company, since it is something they usually test for.

@Sara Malone I feel like some strategy to allow the soil to drain well is mandatory. Raised bed seems to be the way most people tackle this.

Everyone says that garden soil is not container soil, but one thing I have picked up from container gardening is that the best formulas seem to limit the organic component to about 1/3rd of the soil mixture. In gritty mix, that is 30% bark. In commercial container soils based on peat, that is about 30% peat. Using some form of rock/lava/perlite for 1/3rd and some strategy for slower water release like turface seems to balance out the other 1/3rd.

I like the idea of building raised beds with 1/3rd of the native clay soil, 1/3rd drainage rock, and 1/3rd something like a turface. Everyone will disagree with me, and at this point I have heard most of the arguments. The only thing that is 100% certain to me is that my hedges will never do well planted at surface level in 100% native clay soil. Maybe a more skilled gardener could make it work, but it is just too much work, and no one I have paid to take care of that hedge has figured out any way to get them to thrive.

@mad_gallica The pH is around 4.5 for the azaleas. One of the reasons I chose a 50% bark mixture was to keep the soil very acidic.

And the pH of the irrigation water?

Edit: Oh, and what are you using for fertilizer?

Grit is good!

1) Yes, phytophthora, if present and active in your soils, can also affect the photinia.

2) You can submit a soil sample to a professional soil testing lab to determine if phytophthora is present. Not all labs will test for pathogenic issues but here is one locally: Waypoint Analytical. But since it is next to impossible to treat, whether or not one chooses to test for it is up to you....with the problems the plants are displaying you might be just as far ahead assuming it IS present and active.

3) Drainage is almost always improved with the construction of a raised bed, just by virtue of increased elevation. It does not need to be a formally constructed raised bed - a berm or sufficiently deep mound of soil will work just as well. This method is often suggested for those dealing with a poorly draining clay soil.

4) As mentioned in other posts, it is not necessary for all the plants' roots be contained in the raised portions. Most of the important feeder roots are located right below the soil surface with only larger, anchorage roots penetrating much deeper. And they easily have the ability to penetrate even very heavy clay. As long as the drainage is decent where the bulk of the root mass is located, the plant should be fine.

5) If mounding, berming or constructing formal raised beds, you do not have to get fancy with soils mixes or adding turface or even rock or grit. It is unnecessary and overly expensive. Just importing a decent, blended bulk 'garden' soil (available at most bulk soil/landscape supply yards) will work perfectly well.

6) Finally, you can also amend the existing clay soil to improve drainage and water flow. But that is a much longer and more complicated process and needs to be done over as wide an area as possible and without the presence of existing plants. And generally the most frequent recommendation of how to do this is via the addition of coarse organic matter......like bark or unfinished (very textural) compost. The organic matter and the biology it supports will eventually react or combine with the clay to form larger peds/aggregates or individual clumps that allow for voids in between that encourage water percolation and oxygen penetration (porosity and aeration). Just using drain rock, perlite, turface or other non-organic material will not achieve the same results. They do not have the characertistics that will allow for the formation of peds.

Also, plants do not recover from phytophthora. It may not kill them off but they will continue to be infected and show physical signs of the disease - curling or dropping of foliage, dieback of stems or unthrifty and just unhealthy growth and appearance. If the disease is confirmed, you are best removing and destroying the current plants and start fresh with healthy new stock. And maybe avoid those plant choices that are known to be overly susceptible to problems or diseases.

The issue that I find, if I do not add lava pebbles, is that the vast majority of commercially available soils are way too high in organic material to support woody plants as they get established. Within even 3-5 years the amount of decomposition is significant. I don't know why all of these landscape materials places think that we are all just growing vegetables, but there it is. The one vendor who was selling a lower organic % mix has just discontinued it. And I order soil in 20-30 yd deliveries at times. It is very frustrating. Everyone thinks that compost is wonderful, and it can be, but it won't support a tree or even a shrub.

@mad_gallica pH of water is around 6.5.

The hedges were not fertilized, which probably did nothing for their overall strength

@gardengal48 I was hoping that the roots would show a clear area of rot that could be cut out prior to replanting.

@Sara_Malone exactly right. Nearly every person at a nursery tries to create a 100% organic soil or just point you to a mix that is mostly organic.

Even if I just made a soil that was 33% original clay, 33% 1/4-inch crushed rock, and maybe 33% larger-grain sand, the simple increase in drainage characteristics alone - when supported by a raised bed - is going to make the roots breath and grow faster.

Limiting the organic component of well-drained soils to about 30% or less seems to be an important idea.

Just be careful mixing sand and clay. That makes concrete! I'd use the clay, small rock/pebbles and some organic material to help break up the clay. I find that the established plants do fine in the native soil but that it is very difficult to get them started in it. And because most of my garden slopes, it does drain. I grow a lot of large succulents and for them I use maybe as much as 60% pebbles, and often plant them on mounds of single-head stones with the planting medium dumped on top. When there's a will...

@Sara Malone The general recommendation for all-around garden soil is to find a loamy soil. Loamy soils are usually defined as 40% sand, 40% silt (finer than sand), and 20% clay. One such definition is in this page. I was proposing to remove the silt, which would hopefully improve drainage, and go with 33% clay, 33% sand, and 33% 1/4-inch stone. I would be worried that my soil might drain too well if anything.

Clay is loaded with organic material, and mine is mature garden clay with a lot of worms traveling through it. By organic material, do you mean large particles of organic material, such as 1/4 inch bark? What would be the advantage of adding that?

The above soil is proposed for woody hedge plants, such as Pittosporum Tobira.

@Sara Malone I am really curious about your mound building strategy for succulents, and maybe I can try to do that in my garden as an experiment. So you are setting down a stone base? What dimension is that flat stone? I suppose I could just use pavers on compressed base rock. Then you are dumping a standard succulent mix like gritty mix on top of the stone? How could you ever get that to hold a shape of a mound?

No, not flat stones, small boulders (size of a person's head, more or less). I put 3-6 of them in a pile, then dump the planting medium over it. Then plant the succulent in that. Aloes particularly do not like wet feet in winter. It holds its shape ok. Where are you in the SF Bay Area? You could come see if you want - I'm in Petaluma.

Westes, if you are within a day’s drive of Sara’s, go visit. Having seen photos of her garden, I would go in a heartbeat if invited if I didn’t have an entire continent between.

BAbs you are always invited! I can't do much about the continent, though....;-)

@Sara_Malone Your amended soil for those mounds is native clay with up to 50% 1/4" lava pebbles added? Here is a local rockery that sells 1/4" lava. Does that look like yours?

How do you get that to stay in place? Certainly something like gritty mix wouldn't work in that situation and would just blow away over time.

I am near San Jose. If I was closer I would take you up on that! I definitely want to see some photos. Point me to those.

https://formandfoliage.wordpress.com/

I think that when I next visit my sister in San Jose, you may get a message, Sara. Thank you!

@Sara_Malone I had a look at your website. You have an amazing ability to combine color, texture, and shape. Are you doing this professionally or just for your own enjoyment?

Oh it's just me. I'm slightly crazy. I love color more than anything and enjoy combining plants to get interesting and striking combinations. I think that my skill is in plant selection and combination, not in design, which is a really different skill set and to me much more difficult. And I just love plants!

Just an FYI but gritty mix will not just "blow away" :-) Far too heavy! A heavily rock or gravel based outdoor (not container) soil mix will not blow away either......even plain old mounded garden soil will not blow away. Unless you are dealing with hurricane force winds.

Sara and Gardengal48: so if you were going to put Pittosporum Tobira into a raised bed, how wide and how deep would you make the raised bed?

One thing that concerns me if I make the raised bed too big is that it will have a hard time holding onto water. I'm concerned it might drain too well and too rapidly for this type of plant.

I make mounds - gradually sloped. The type of material will determine how fast it drains. Once a good root system develops it will help hold onto the water.

For mounds, I understand your point. But mounds usually take a larger width to allow for that gradual sloping down. I have a very narrow strip to work with. So if you were forced into using sharp vertical walls to contain the raised bed, with the bottom open to the native soil, how wide and tall would you make it for Pittosporum Tobira?

I see. I'd make the bed as wide as possible. Maybe2' high? 18"? The other thing that you can possibly do is to make your mound and use rocks in a more informal way to hold the soil in. Not a wall but groups of rocks. You may not have enough space for that, either. If the space is so narrow, is this the right plant?

@sara_malone So maybe 4 feet wide and 18" to 24" high? With roots in the ground the plant had plenty of space to grow the roots out. But the space available for the part of the plant above ground is limited.

The height probably should be determined by how high it needs to be to restrain the soil. Boards come in 12" width I think so that may be a factor too if you don't have the ability to rip a board in half lengthwise.

@Sara_Malone what do you mean by restraining the soil?

Keeping the soil in the bed.

@Sara_Malone you mean just observe the height of the root ball when I replant the existing hedges, and obviously the raised bed box needs to be a little higher than the height of that root ball?

Yeah basically. And consider the aesthetics as well. The height should look pleasing vis a vis the width and depth. The depths is going to be determined by the space that you have, and the length by how long you need it to be to include the shrubs. So determine that first and then see what you can play around with for the height.