Wednesday, September 13, 2023

A predictable casualty?

As summers go, this hasn't been a bad one.  Yes, we've had heatwaves but my area hasn't experienced any temperatures of 100F or higher this year.  And Tropical Storm Hilary filled my empty rain collection tanks in August, which was a major boon!  So when I noticed yellow and brown leaves on a tree-sized shrub in my street-side border I was surprised.  When I took a closer look at it I was appalled.

The 2 tree-sized shrubs on the far right are Auranticarpa rhombifolia (formerly classified as Pittosporum rhombifolium, commonly known as diamond leaf pittosporum)


Just weeks ago, I'd looked at the now-sad shrub and thought I should prune the lower limbs to allow the succulents planted below to get more sun.  I hadn't noticed any signs that it was at death's door.

This is the wide shot I took of the area in early July.  The foliage may be slightly yellower than the shrub next to it but, if I noticed that at all, it didn't strike me as a dramatic difference.

 

The Auranticarpa planted directly to the right of the dead one still looks healthy.

These photos provide a direct comparison of the 2 shrubs

A closeup of their foliage tells the story more clearly.  The plant on the right is also producing a generous crop of berries, while there are virtually no berries on the plant on the left.

 

I don't know what caused this particular Auranticarpa to die off but there's a long pattern involving the plant so, while I'm disappointed, I shouldn't have been all that surprised.  I inherited numerous Auranticarpa shrubs with the garden.  According to online sources, the plants are native to the rainforests of Eastern Australia.  I couldn't find anything describing their drought tolerance but, given the plant's ancestry, it may not be the best one for a drought-persistent landscape.

 

When we moved in, close to half the street-facing hedge on the south side of the driveway consisted of  Auranticarpa rhombifolia.  The remainder consisted of Xylosma congestum, the shrub that also makes up the entire hedge on the left side of the driveway, as well as the the hedge lining the main level of the back garden.  I thought the mix of hedge material on the south side of the front hedge was odd.  When three of the inherited Auranticarpa began to decline on my watch, a neighbor told me that the prior owners had originally planted the front area entirely in Auranticarpa but removed the majority of these when the plants started dying, replacing them with Xylosma.  After failing to resurrect the dying shrubs, my husband and I removed three Auranticarpa in 2016 and another two in 2020, filling in the gap created by their removal with succulents and five additional Xylosma.

This photo taken in May 2016 shows the area after 3 of the Auranticarpa were removed and 4 of the five new Xylosma had been planted

This photo from May 2020 shows the area after 2 more of Auranticarpa were removed.  The 5 "new" Xylosma were gaining height and girth by that time but their development was slower than expected.

This photo shows the 2 remaining Auranticarpa as of May 2020

 

 

My husband may elect to remove the dead Auranticarpa himself but, if not, I'll include it on the list for the tree service to handle when our trees receive their annual pruning.  I'm tempted to give up and remove the last remaining specimen in this area but it sits on the edge of the property line with our south-end neighbor so I'm hesitant to proceed there, especially as it's still healthy.  There are also three other Auranticarpa elsewhere in our garden that seem fine.

 

My garden has actually received substantially more rainwater than usual this year, 23.74 inches in total since the start of the 2023 "rain year" on October 1, 2022.  In contrast to the Auranticarpa, other shrubs are thriving.

The "new" Xylosma have finally reached almost the same height as the original plants on the left.  The newer plants were set slightly further back to allow room for the succulents I'd planted, creating a bend in the hedge.

In addition, I think Jacaranda 'Bonsai Blue' has gained another foot in height since Tropical Storm Hilary passed through


If there's one lesson here, it's that nothing much is predictable when it comes to the evolution of a garden.



All material © 2012-2023 by Kris Peterson for Late to the Garden Party

12 comments:

  1. Nature throws your a curve ball every now and again. The silver lining, if there is one: you didn't spend a morning pruning the lower branches... The remaining Auranticarpa looks healthy as they come. My vote (if I have one :-D) is for it to remain, like the warrior that it is.
    I'm also rooting for Jacaranda 'Bonsai Blue', a reminder of my childhood. Will you eventually grow it with a single trunk?
    Chavli

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    1. As I don't want to annoy the neighbors, I expect the healthy Auranticarpa in the front garden will remain in place until it elects to exit on its own terms, which is probably inevitable. As to the Jacaranda, it's a dwarf meant to stay relatively small so I'll probably leave it alone to do its bushy thing, Chavli. I can't let it get too tall as my husband will mount a protest - he already complains about my plants blocking his view from his favorite living room chair.

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  2. How odd it kicked the bucket during a rainier year! The berries look lovely on the healthy one.

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    1. When I see a relatively fast decline like this I usually blame the pathogen that causes sudden oak death, which affects a large number of plants in addition to oaks. However, my Sunset Western Garden Book says that this particular plant is resistant to oak root fungus so I'm clueless about why these plants are prone to dropping dead, tz :(

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  3. That is the lesson for sure, plants do what they do whether it makes sense to us or not. What really jumped out to me in this post is the fact you had more rain and cooler temperatures than we had this summer. Crazy times.

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    1. Well, our only real summer rain (2 inches here) arrived courtesy of Tropical Storm Hilary but, if the ocean temperatures to the south of us continue to rise, I'm guessing that there may be more such tropical storms in our future. As it is, El Nino conditions are expected to bring us more rain during our usual rainy reason in the 2024 "water year" which starts October 1st.

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  4. With our hotter and drier weather this summer, I am losing a lot of things fairly suddenly. I am going to blame the weather and not me. In my garden, heavy seed production tends to mean a tree or shrub thinks it’s going to die and is sending out progeny for the future.

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    1. I usually assume the problem is too little water, Linda. In fact, my knee-jerk response when I noticed that the shrub was tanking was to water it but, in this case, given the plant's long history, I think its death was preordained.

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  5. Is it a dead shrub, or is it a...plant shopping opportunity?

    More seriously, here the 'Marjorie Channon' Pittos were gorgeous for a while---and then they weren't. Perhaps shrubs that have evolved in cooler wetter climates are not viable long term in SoCal. That drought we had for years surely abbreviated their life span.

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    1. Ha! I never need to look far to justify plant shopping opportunities, HB. As soon as we're on solid ground with cooler temperatures, it'll be time to get out there again!

      As I inherited the Auranticarpa/Pittosporum with the garden, I never looked up its background until now. Plants native to rainforests don't seem like good matches for our climate!

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  6. The top three things that I see kill established landscape plants suddenly are drought, disease, or insects. Drought damage has been happening a lot here in Oregon too, killing conifers like arborvitae, western red cedar, grand fir, and Nootka cedar. Sometimes the roots of evergreen trees are damaged during the previous year's drought and it just takes a while for the top part of the plant to die.

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    1. I think your last statement gets to the heart of the problem with the Auranticarpa, Jerry. Maybe it can handle infrequent drought but, as a rainforest plant, persistent drought can't be remedied with heavier rainfall now and then.

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