I have been back nearly two weeks but do not have much to say about my garden. I am still clearing out annuals that have flowered, gone to seed, and dried up. The tomatoes are growing into a tangled mess that needs to be staked. The grapes, heavy with green bunches, are reaching out, ready to clamber over neighboring shrubs and trees. But for the most part, the garden is holding its own.
The South Pasadena Arroyo Seco Nature Park, on the other hand, has been a real challenge. This year has been unusually wet and cool which is nice for my home garden – except for the tomatoes – and nice for the weeds at the park. For the first time in a few years we found quite a few castor bean seedlings (Ricinus communis), not a big deal so long as we keep on them. Many of the other weeds that are overwhelming the park are more difficult to control. These include tumbleweed (Salsola tragus), mustard (Brassica nigra, or is it Hirschfeldia incana?), horseweed (Conyza sp.), horehound (Marrubium vulgare), and, argh, tocalote (Centaurea melitensis), just to name a few. But I am not here to complain. Rather I would like to talk about trees that fall over.
Over the years several trees in the park have split and fallen over. The first was a large western sycamore (Platanus racemosa), next a blue elderberry (Sambucus mexicana), and most recently another large western sycamore. So what is going on and why doesn’t the city remove the dead trees?
The Nature Park, created in 2004, was intended to provide natural habitat for the respite of people and critters in our urban environment. Fallen, decaying trees are an important part of good habitat. Insects that help in the process of decomposition are themselves food for birds, lizards and other animals. The horizontal limbs provide shelter for small scurrying critters, little flittering birds and a myriad of insects. And finally, it seems that fewer weeds appear when the fallen tree is left in place. For these reasons the messiness of fallen trees is preferred to the neatness of gardens, even those populated by native plants.
The first western sycamore to topple in the park leaned precariously for quite a while before it fell over. It took some convincing to get the city to remove the part that was blocking the trail while leaving the remainder. Since that time an erect and sturdy shoot has emerged from the root system near the original main trunk. The fallen trunk supports many sprouts that make it look like a candelabra. Lizards scurry through the slowly decaying fallen branches. Had the tree been cut up and put through a chipper, I am sure we would have been fighting a whole new infestation of weeds.
Just one year later the sprout is growing straight and tall while smaller branches grow from original main trunk. (photo taken: 5/9/09)
Next a portion of a large blue elderberry split and fell during a heavy rain. The area is “messy” with decaying wood but new growth is vigorous and weeds are not taking over the area.
The most recent sycamore to bite the dust fell in two distinct episodes. The tree had two main trunks and over the years I enjoyed watching bees fly into and out of the cavity in between. If the tree were in my yard I would have been concerned, but here in the Nature Park it was no problem. It would split and fall when it was good and ready, and this year was its time. The bees are gone now that the cavity split wide open but like the other fallen trees, there is lots of new growth from the old root system.
Broken limb of sycamore (photo taken: 3/19/11)
Abandoned bee hive in cavity of sycamore before the tree split. (photo taken: 4/11/09)
It does not look like any of these trees died from disease, rather they fell due to poor growth such as crossed limbs and split trunks. Split and broken trees occur in all natural woods. In gardens and parks we attempt to prevent such events with preemptive pruning practices because they can cause damage to property and a loss to the landscape. In wild areas these events are a fact of life that should be observed with interest rather than disappointment or despair.
Spend some time in the Nature Park. Pull a few weeds, observe some birds, talk with your neighbors, and just plain enjoy!