Hidden by too much ‘mulch,’ crown rot revealed by wind gust
With almost no roots left to hold it in place, this photinia fell over in Saturday's storm.
Debbie Arrington
Why do trees (or large shrubs) suddenly fall during a big storm? The problem often lies at the roots.
Right after warning Sacramento Digs Gardening readers about trees that are leaning, I lost one of my 12-foot photinias. Blasted by wind, it fell over during Saturday’s storm.
This was a red-tip Fraser photinia – one of the most common hedge shrubs in Sacramento – and seemingly healthy. As an evergreen, it still had lots of foliage. And that canopy also was part of what led to its sudden downfall; the broad leaves apparently caught a sudden gust and that toppled the tree right over.
My first thought when I saw it: How do I get this big shrub up and stabilized? But this photinia was a goner.
On closer inspection, I discovered the photinia had snapped off at the base of its multi-trunks – it was a victim of crown rot. Only one healthy (albeit very thick) root had been holding the tree upright. There were signs of rot all around the crown (where the trunks meet the soil).
Unfortunately, it took the shrub falling over to reveal the rot. And I feel partly responsible.
Planted when our home was built in 1980, the photinia was under a gigantic coastal redwood that hangs over the fence and dumps loads of debris. That redwood litter had accumulated between the fence and the trunk of the photinia, mounding around the crown.
While the redwood litter mulched the shrub and helped it through drought, it also kept too much moisture around the crown, allowing fungal disease to take hold. (Yes, you can have too much mulch.)
Crown rot is caused by funguslike water molds, according to the UCANR pest notes. Above-ground signs of this infection include twig or branch dieback, undersized or discolored leaves and dropped foliage. Mature shrubs or trees infected by these molds grow slowly and gradually decline.
My photinia had shown some twig dieback, but I attributed this to the drought. It also grew much slower in recent years; for a shrub that needs regular pruning, I thought that was a good thing.
But now there’s a wide hole in my photinia hedge. While I couldn’t save the fallen photinia, I’m raking out that redwood debris from under the remaining shrubs so their crowns can dry out.
For more on crown rot: http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/DISEASE/pchphytoph.html.
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Dig In: Garden Checklist
For week of Sept. 24:
This week our weather will be just right for fall gardening. What are you waiting for?
* Now is the time to plant for fall. The warm soil will get these veggies off to a fast start.
* Keep harvesting tomatoes, peppers, squash, melons and eggplant. Tomatoes may ripen faster off the vine and sitting on the kitchen counter.
* Compost annuals and vegetable crops that have finished producing.
* Cultivate and add compost to the soil to replenish its nutrients for fall and winter vegetables and flowers.
* Fertilize deciduous fruit trees.
* Plant onions, lettuce, peas, radishes, turnips, beets, carrots, bok choy, spinach and potatoes directly into the vegetable beds.
* Transplant cabbage, broccoli, kale, Brussels sprouts and cauliflower as well as lettuce seedlings.
* Sow seeds of California poppies, clarkia and African daisies.
* Transplant cool-weather annuals such as pansies, violas, fairy primroses, calendulas, stocks and snapdragons.
* Divide and replant bulbs, rhizomes and perennials. That includes bearded iris; if they haven’t bloomed in three years, it’s time to dig them up and divide their rhizomes.
* Dig up and divide daylilies as they complete their bloom cycle.
* Divide and transplant peonies that have become overcrowded. Replant with “eyes” about an inch below the soil surface.
* Late September is ideal for sowing a new lawn or re-seeding bare spots.
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