From Aleppo Pine to Silk Tree

mimosa tree on Burbank Blvd, just west of 405 Freeway

“For about 8 years we enjoyed a lovely Aleppo pine on my hillside yard.  This tree was purchased in a large box and was quite mature when we brought it in and it flourished for many years.  We have had several types of pines in our yard over the 30 years that we 

have lived in our coastal community. When the development was first built in the early ‘60s, they brought in many Monterey pines but they struggled when we had dry periods.  Most of the original  Monterey pines have now died off, some from disease and some from old age.  The Aleppo reportedly could stand long dry spells and could easily be kept to a lower profile which is a goal for protecting the beautiful ocean and city views in our neighborhood.
“This year when the rains came, I noticed that the Aleppo seemed to start to droop.  By December about 1/3 of the needles were dry.  In January I called the arborist we have used for decades. He claimed the tree had acquired root rot and that it would unlikely survive the upcoming season.
“Now we are getting ready to have it removed since it is completely dry.  Through some research and at the advice of the arborist, we have been planning on digging out the tree along with as much soil as we can.  We were told that the root fungus can live a long time in the soil and that it should be changed out before bringing in another tree.
“We are considering perhaps something other than a pine.  The location gets sunrise to early afternoon sunlight and we would like something that will naturally stay at about 30-35 feet in height, though we are happy to trim it annually to maintain the height restriction.  Currently we like the profile of a tree where there is about a 12 to 15 foot trunk height and then the canopy.  That allows us to see our beautiful view under the tree and then gradually up through the branches.
As much as we loved our pines, perhaps a flowering tree or similar would be a nice change for us.”
Greg McMurry, Pacific Palisades
Your email raises many interesting questions and issues.  First and foremost among them is why, after flourishing for 8 years, did your Aleppo pine suddenly die?
Since its decline began with the onset of this winter’s heavy rains, it would seem likely that the rain had something to do with its demise.  You mention a soil fungus although soil fungi are usually activated in warm weather and your tree’s decline began in the winter.  In addition, Aleppo pine is on the list of trees resistant to the most devastating fungus in our area — known as oak root fungus (Armillaria mellea) — when it comes to sudden death of trees.
I think it’s also possible that the soil on your slope became saturated from the rain and the roots of your Aleppo became waterlogged.  Roots need oxygen as much as you and I and when they become waterlogged, they are susceptible to suffocation and to subsequent invasion by anaerobic bacteria, which lead to root rot.  Aleppo pine is native to the Mediterranean and gets its name from Aleppo, Syria, where the average annual rainfall is 12 inches, or nearly 7 inches less than the amount of rain that fell this winter in Los Angeles.
One way to tell whether the culprit is fungus or bacteria is by conducting a smell test, if you can dig up some of the soil around the dead roots of your tree.  Anaerobic bacteria smell like rotten eggs.  An interesting side note is that all bacterial plant diseases, from bacterial leaf spot to stem canker, have an odor of one kind or another, which is a handy way of labeling or eliminating bacteria as the disease agent when investigating the cause of any particular disease.
If your soil did not drain well, I highly doubt your Aleppo would have survived for eight years as I am assuming you gave it supplementary irrigation during the long period of drought prior to this year’s winter rain.  More than likely, you experienced a one time event where sudden excessive moisture — more than 8 inches of rain fell in January alone — brought on waterlogged and rotted roots.
It might be wise to send a soil sample to Wallace Laboratories in El Segundo.  Included in their standard test, which costs $80, is an evaluation of pH, fertility and other soil properties, along with recommendations for soil improvement.  Details for sending in a sample may be found at
I remember taking a tour of Wallace Labs many years ago and learning that gypsum is one of the best soil amendments for local use.  Our soil tends to be overly alkaline and gypsum has an acidifying affect.  You can mix gypsum into your soil when planting and then apply it topically several times throughout the year.  The fact that gypsum is probably the least expensive of all soil amendments is an added bonus.  Just make sure you wear a dust mask when handling it since its texture is fine and powdery.
There are two other issues which might not have anything to do with your particular tree but should be raised nevertheless.  You mentioned that your Aleppo “could easily be kept to a lower profile” which, I assume, meant that it could be regularly pruned.  Actually, it is not advisable to prune pine trees.  Much like oaks, cutting into the wood of a pine tree is not a good idea, even though I am aware that plenty of pine trees are regularly pruned without apparent ill effects. Nevertheless, such woody cuts are still not recommended since they can invite pests and disease organisms or simply lead to weakening of the tree in general.
Another issue concerns the quality of the tree that was planted.  You say it was planted from a large box which always raises the question of whether it could have been pot or root bound.  Just because a tree has been in the ground for 8 years does not mean it is no longer susceptible to death from a pot or root bound condition when it was planted — that is, roots were circling the container in which they grew, were not broken up at planting time, and never grew out into the surrounding soil.  In the words of veteran nurseryman and tree grower Akiva Silver, “Often pot bound trees will strangle themselves with a girdling root 10 or 20 years after planting.”
Be careful, especially, about acquiring trees under power lines from amateur growers.  Their prices may be low but that can mean that their trees have been sitting in their boxes for years and developed a root bound condition.  One nursery that I would strongly recommend is Norman’s,  whose headquarters is in San Gabriel.  Norman’s does not sell to the public so you will need to go through a landscape contractor.  Ask your contractor to email you photos of the trees you are considering to eliminate any surprises upon delivery.
As for alternative species that meet your specifications, it sounds like you are in search of a tree with an umbrella form.  Due to the shade cast by the canopy of such trees, there is no growth on underlying branches so you will have a clear view through them.    Three trees come to mind.  Silk tree or mimosa (Albizia julibrissin) grows quickly to a height of thirty feet.  It has unusual wispy pink flowers whose shape reminds me of a badminton shuttlecock.  Gold medallion tree (Cassia leptophylla) is also a fast grower to about the same height.  It will require a bit of training to adhere to the umbrella form.  Not only are its golden flowers a dazzling adornment this time of year, but they are followed by dark brown pods that you can’t miss since they are a foot long.
Australian tea tree (Leptospermum laevigatum) is another possibility.  Branches are of sculptural interest as they twist and turn away from the trunk.  Leaves are small, elliptical, and grayish green, neat, decorous and soft to the touch.  This foliage offers a stark contrast to the tree’s bark, which is shaggy and unkempt.  Australian tea tree is a misnomer in the case of this species, however, since the famous Australian tea tree oil does not come from it but from a related species (Melaleuca alternifolia).
Tip of the Week:  Both silk and gold medallion trees are legumes so they will not require fertilization.  Their seeds are easily germinated following a soak in a cup of water that has just been boiled.  Keep them in that water, as it cools, for 24 hours.  Seeds that float on top of the water have no embryos and should be discarded. Seeds that sink have embryos and should be planted in any well drained soil mix at a depth equal to their length.  Seed coats of drought tolerant trees tend to be hard and impermeable in order to withstand years of drought, but treatment in hot water usually opens them just enough so that a tiny root and shoot can break through.  However, some leguminous seeds, such as mesquite seeds, are so hard that they need to be soaked in sulfuric acid in order to sprout.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.