Ficus Tree pruning and fire danger

Question from Ann:
I have a few large ficus trees (25-30 ft tall) that are providing shade and a very dense privacy screen from my neighbor. I want to top the tree in the fall to 15 ft which will hopefully fill in for shade the following summer. I’m worried about fire danger since I live on a hill in a high fire danger area. An arborist was against topping, stating this would cause the lower leaves to drop and I’d lose my privacy screen. Will the lost leaves eventually fill in?

Your advice is greatly appreciated.

Answer from Pat:
In order to advise you intelligently I need to know what species your ficus trees are. Some ficus species lend themselves for use as screens and others do not. Weeping fig (Ficus benjamina), for example, often begins life as a houseplant and later is planted outdoors. Leaf drop often occurs when moving this tree from indoors to outdoors or when it goes too dry. I have not seen leaf drop occur as a result of pruning. It can be pruned into a large hedge or screen. Indian laurel fig (F.microcarpa) also takes to pruning as a hedge. I have seen as much as ten feet cut from the top of these species when they are already growing as a screen or hedge and there has been no leaf drop as a result. Either of these species can be topped and sheared when grown in appropriate climates and kept watered.

Moreton Bay fig (F. macrophylla), however, is an enormous tree and does not lend itself to hedging. This species needs careful and knowledgeable pruning. Topping a Moreton Bay fig would severely harm it and destroy its shape. Rustyleaf fig (F. rubiginosa), a commonly planted garden tree, is densely foliaged but in general not a good subject for a hedge or screen. This tree also can be harmed by over-pruning but I have seen it extensively laced out without harm. I have also seen it drop-crotched in order to lower the height. In this case it took a few years to recover. F. rubiginosa drops many figs. They get onto sidewalks and can get tracked into the house.

There are many other ficus species other than the ones I have mentioned here in addition to dozens of named selections. Since your arborist suggested the lower leaves might fall off if you topped the tree, this sounds to me as if he thought the pruning you contemplate is too drastic. Instead of topping the trees so drastically, why not drop-crotch the tops of the trees and prune more lightly, pinching back all branches. This should stimulate growth lower on the tree without shocking the tree into loss of foliage, but first think about this a bit more and decide if this is really what you want to do.

Perhaps your idea to lower the trees to save them from fire damage might be the wrong approach to fire protection. Consider this: Though any tree can burn in a hot enough fire, rubber trees are not high on the list of combustable trees. Pine trees, eucalyptus trees, cypress trees, and palm trees are far more combustible than ficus trees. Additionally, trees that have foliage lower to the ground are a greater danger than those that have tall trunks with foliage lifted high off the ground. One thing to avoid is a “ladder” effect made by plants offering a way from ground fires to jump up from the ground and spread into the tops of trees. In a recent fire in San Diego county a ground fire burned through the neighborhood. On one lot it burned down the house and it burned all the plants on the ground but it left three or four free-standing ficus trees. These were rustyleaf fig trees (F. rubiginosa), and they were barely singed. They were left standing on the lot with no apparent damage to them. This would indicate that though ficus trees may not be a defense in a wild fire, most likely they do not pose a danger either.