|City workers removing toppled oak tree on Sunday, June 16, 2013|
This fungus is common in southern California soils, especially in areas that receive supplemental, summer irrigation. Although the fungus caused the roots to rot, it was the pervasive wet soil conditions that provided the perfect environment for the disease to thrive. Oaks grown without summer irrigation are much less likely to succumb to this and other diseases.
|Weakened roots in soggy, compacted soil fail to support the tree.|
|Notice water collecting around the base of this tree. This is common in Garfield Park.|
The soggy grass in Garfield Park is totally incompatible with coast live oaks and many other trees and plants. I frequently jog in the park and I know that the soil never dries out, not in winter or summer. Mud puddles occur, even surrounding some mature oak trees. Grass extends right up to the base of many oaks, an especially bad horticultural practice.
|Grass extends right up to base of these trees. This is extremely damaging to coast live oaks (and other trees).
Notice the moss growing around the lower trunk.
|It is even too wet for the grass to grow under this oak. The picture was taken at around 5 PM on Monday.|
|Replacement oak doing poorly with
grass covering its crown. We need
to decide whether we want grass or
magnificent trees and act accordingly.
Although one could just shrug one’s shoulders and say, another died from Armillaria, in fact it is our excessive watering, especially in summer, that killed and will continue to kill these trees. It is not certain whether any will survive after all of these years of abuse, but if we want to preserve these beautiful trees we must stop maintaining the park as though the only important plant is grass.
I consulted with a specialist at Rancho Santa Ana Botanic Garden about the best way to save the remaining trees. He suggested that trees that pre-date the creation of the park should receive no additional water, going “Cold Turkey.” Their deep, extensive root systems already reach ground water, though the surface roots may be rotted. Trees that have matured with summer irrigation should be weaned off it more gradually.
The grass around the trees should be allowed to die and leaf litter to accumulate. Since the park is so heavily used, it may be a good idea to protect the oaks from further soil compaction by either roping off the area under the trees until leaf litter provides a protective cover, or adding organic mulch (keeping the trunk of the trees clean and clear).
There are some beautiful trees in Garfield Park. We need to decide whether we want to preserve them, or whether we prefer a less shady but very green and thirsty field. In fact we can have both since so many oaks have already died. Maintain grass in the open central areas, while cutting off water around the oaks.
Last night I went to the Natural Resources and Environmental Commission meeting to try to convince them to recommend to City Council a change in maintenance for this park. The Park Supervisor was present and he made it clear that they are way ahead of me. Gonzalo Maravilla reported to the commission that his crew was in the park checking the irrigation right after the loss. They have already turned off sprinkler heads that were located within groupings of trees. The sprinkler heads outside these groups have been adjusted to spray away from the trees. Mr. Maravilla plans to allow mulch to accumulate but will spread some now to protect the soil from further compaction. The focus will be on two groups of trees at the south end of the park, on the east and west corners.
It is likely that more oaks will fall, though these attempts to alter the soil conditions are important steps to preserving them. And finally, a word to my fellow South Pasadeneans: Don’t call the city to report that the grass in the park is doing poorly because they are trying to strike a good balance between the need for grassy fields for recreation and the need for beautiful trees for shade, beauty and habitat.
|Imagine sitting at the picnic table without this beautiful oak.|
|Shady spot with leaf litter cover. People seem to be comfortable
on this surface and it is much healthier for the trees.
|Magnificent oak fell during the windstorm of 2011. We can blame the winds, but these trees did not
have a chance living in wet soil with rotted roots. If we do not change the conditions in Garfield Park
there will be many more losses.