GARDENING\Planting trees can be first step toward a better world.

Byline: Joshua Siskin

"You can tell the health of a country by the health of its trees."

"Show me an area without trees, and I will show you an area of unrest."

These statements by Dr. Alex Shigo, an internationally recognized authority on trees, are full of sad truth, but also of realistic hope. The truth is in the correlation between the health of neighborhoods and the health of the trees that grow in them. Where there are few trees in a certain part of town, that's where you're likely to find unrest. In cities, urban blight visits neighborhoods where trees are blighted, slighted or absent altogether.

Yet, hope is in the proposition that underlies Shigo's words: Plant trees and neighborhoods will get well again. Plant trees and people will be healed.

Trees pacify the landscape and the cityscape. They provide a buffer against winter wind and summer sun. They are images of stability and tranquillity, contradicting the hectic and the chaotic, the traffic and the noise.

Let's not just plant trees in Los Angeles. Let's be very specific and plant California live oaks, trees native to this area that will be here a long time and live in harmony with their surroundings.

Can you imagine what this city would be like today if some visionary mayor 50 (or even 10) years ago insisted that more oaks be planted in Los Angeles?

Yes, these trees get massive, but so much the better. The old oaks that sill stand in the Valley - at Ventura Boulevard and Louise Avenue, at Balboa and Magnolia boulevards, or at Orcutt Ranch - are beloved by those who live or work near them. There is nothing that enhances the quality of life more than a California live oak. Can you imagine if there were just a thousand more of these trees scattered around?

There are too many mophead palms in this city. They symbolize easy money and contrived elegance. Let's replace every palm with an oak tree and transform the ethos of our city.

Shigo informs us city dwellers that we really can't understand trees because "trees became trees not as singles but as groups." The ecosystem of a tree is a forest. Our uphill fight to grow individual specimen trees - in asphalt, in concrete, or even in the back yard - is understandable, considering the adverse surroundings that they face. So let's plant urban forests and find out what trees are all about.

The oak forest in Descanso Gardens needs to be planted several times over. Every time I read about downtown L.A. and what needs to be done to save it, I think, "Let's start by planting a forest there, a Bois de Boulogne. Is there anyone who wouldn't want to live or work next to a forest?"

The longevity of oaks, sycamores and redwoods is explained by their capacity for self-healing. When a limb breaks off one of these trees, wood that protects against disease is formed right at the breakage point, near the outside of the trunk. Short-lived tree species form protection wood further inside the trunk, making them more susceptible to disease and decay. This is why the life expectancy of Prunus trees - peach, apricot, plum, cherry and almond - is only about 40 years; they are not very good at healing themselves.

Another secret of trees' success is their ability to mix with different communities. This is especially true, said Shigo, in relation to the communities of organisms that live in the soil. The soil bacteria with which tree roots live provide systemic defense against pathogenic fungi and insects, also in exchange for carbohydrate manufactured by the tree.

When we plant the great Los Angeles Forest and learn how it works, the city that is built around it will be a community from which all can benefit.

Tip:According to Shigo, once a tree is established, it should not typically require fertilization. (Fruit trees, of course, are different.) Also, he said, trees can be pruned at any time of the year as long as they are pruned correctly. Finally, never root prune a tree. The tree could fall over and, even if it doesn't, you will have taken away its dignity and may as well remove it completely.

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Photo Trees pacify the landscape and the cityscape. They provide a buffer against winter wind and summer sun. They are images of stability and tranquillity, contradicting the hectic and the chaotic, the traffic and the noise.