Protecting the Urban Forest

Anna's hummingbird

A week ago the ironbark tree across the street burst into bloom. It was one of the few ironbark or eucalyptus trees in the neighborhood that was doing well. Most have been severely impacted by CA's continuing drought.

The blooming tree was an oasis for migrating birds - Hutton's vireo, Anna's hummingbirds, yellow-rumped warblers, Townsend's warbler, a black-throated gray warbler, and ruby-crowned kinglets. All of these species were documented in a single morning last week. The resident Allen's hummingbirds were also imbibing of the flower nectar. This single tree was providing natural food and sanctuary.

This morning the ironbark and its neighboring red gum eucalyptus are savagely reduced to skeletons. The red gum has been poorly trimmed before. Because of it, its shortened limbs have been forced to send out new growth that is unstable and tends to break off in winds. To reduce the dropped limbs the home owner made the same mistake again, repeating a cycle of mismanaged trimming that will cause this tree to regrow fragile limbs and result in shortening its life. Each chopped off limb is now open to insect and fungal invaders. It is a cycle I have witnessed throughout my neighborhood for twenty-five years.

Twenty-five years ago our neighborhood was renowned for its tree-lined streets. We were typically cooler than other neighborhoods. Today 90% of our large trees are gone and Woodland Hills frequently records the hottest temperatures in the west San Fernando Valley.

In the remnant of a single blooming branch a small Hutton's vireo sat bewildered. (circled in green)

How do we stop deforesting our urban forest? How do we teach people the value of their trees and the shade they provide? What steps can we take to plant trees that both provide habitat for native wildlife and are compatible with urban needs?

Who speaks for the urban forest?

Success With a Native Plant - Western Redbud

Isn't it beautiful?

This western redbud (Cercis occidentalis) is blooming in our north-facing front yard. Our success with native plants has been sporadic. Planting this redbud was part of a long-term plan to replace an ornamental plum tree that was declining. We loved the spring blooms, but the increasing summer heat in the San Fernando Valley had become too intense for the plum.

Five years ago I planted a 5 gallon redbud in the dappled shade of the older tree. Gradually the plum was thinned to provide the redbud with more light. I wasn't sure that the plan was working. The redbud was still small and didn't flower much.

Just over a year ago, the plum became precarious. We were sad to see the old tree go, but it was dying and riddled with termites. The tree trimmers carefully removed the old tree without harming the four-foot redbud.

Over the summer and fall, the redbud grew several feet and really came into its own. With the winter rains, it has burst into brilliant purpley blooms. The redbud hasn't completely filled into the spot in the yard vacated by the ornamental plum, but it will. Finally, a real native plant success.

other natives doing well:
ceanothus  
white ceanothus
Douglas iris
Douglas iris and gophers 

Managing Your Backyard Treescape

Daintree Rainforest, Cape Tribulation, northern Queensland, Australia

When you look into a forest, like the rainforest in northern Queensland Australia, it can be hard to see the individual trees from the forest. 

In man-made woodlands around our homes and workplaces, we get used to a specific look–big tree with smaller shrubs and ground covers. But a wild forest is forever changing and there is a progression of plants: small trees growing up under still standing larger trees. Too often we forget that trees have a lifespan or can be compromised by drought, disease, or poor management.

In our neighborhood we have seen these three variables reduce the large trees dramatically over 20 years. Our once tree-lined streets, now are sunny and mostly treeless.

During a botany walk a few years ago with representatives from some of the major botanical gardens in Southern California, I learned a valuable lesson–think like a forest and plan for succession of large trees. Several of these destination gardens had learned the hard way that wind storms and unexpected disease can wipe out your man-made forest in short order and regrowing those valuable trees takes time.

I know I have two trees that are past their prime. Our flowering plum tree (Prunus cerasifera) can put on a beautiful display in spring, but it is not a long-lived species and termites are now compromising this tree. She probably has a few more years, but it is time to think about succession. What will take this tree's place? Five years ago I planted a native redbud (Cercis occidentalis), just down hill of the plum tree. Finally, it is really taking hold and starting to grow. It too will offer flowers in the spring, but it will also offer food to native birds and insects. And three years ago I discovered a native coast oak (Quercus agrifolia) coming up as a volunteer. I'm grooming these two trees to take the place of the flowering plum.

Last year the arborists discovered a hollow in the Chinese elm (Ulmus parvifolia) that threatens to weaken the tree over the next few years. It will be a loss to our backyard shade when it goes, but we are planning ahead. We planted a native California sycamore (Platanus racemosa) just uphill to eventually take the elm's place.

Succession is natural in wild landscapes and with a little thought, you can make it natural in your landscape as well.

green ant from Australian rainforest

Intrigued by the Australian rainforest. 

Take a 1 minute escape to this far away landscape at TheEarthMinute.com