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.
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 March 19:
Spring will start a bit soggy, but there’s still plenty to do between showers:
* Fertilize roses, annual flowers and berries as spring growth begins to appear.
* Watch out for aphids. Wash off plants with strong blast from the hose.
* Pull weeds now! Don’t let them get started. Take a hoe and whack them as soon as they sprout.
* Prepare summer vegetable beds. Spade in compost and other amendments.
* Prune and fertilize spring-flowering shrubs after bloom.
* Feed camellias at the end of their bloom cycle. Pick up browned and fallen flowers to fight blossom blight.
* Feed citrus trees as they start to blossom.
* Cut back and fertilize perennial herbs to encourage new growth.
* Seed and renovate the lawn (if you still have one). Feed cool-season grasses such as bent, blue, rye and fescue with a slow-release fertilizer. Check the irrigation system and perform maintenance. Make sure sprinkler heads are turned toward the lawn, not the sidewalk.
* In the vegetable garden, transplant lettuce and kale.
* Seed chard and beets directly into the ground.
* Plant summer bulbs, including gladiolus, tuberous begonias and callas. Also plant dahlia tubers.
* Shop for perennials. Many varieties are available in local nurseries and at plant events. They can be transplanted now while the weather remains relatively cool.
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