One of the Best Flowering Trees!

Back in my college days at Cal Poly Pomona, I took several plant identification courses as part of the educational requirements for Ornamental Horticulture.  Two trees from the same genus always stood out for their outstanding floral display and landscape use.  Back then, the genus was called Tabebuia, since changed to Handroanthus. The two useful landscape species are Handroanthus impetiginosa,(Pink trumpet tree) and H. chrysotrichus, (Golden trumpet tree).

The Pink trumpet tree in full bloom

While taking a walk, I came across a beautiful pink trumpet tree in full bloom.  I then started noticing a few other trumpet trees scattered about the neighborhoods in North Park.  I’m not to sure why, but in my view, this species is an under utilized ornamental landscape tree.  Perhaps due to a slow growth rate, medium appetite for water or its deciduous nature, the species is not heavily promoted by the nursery industry.  But it has many beneficial characteristics making it a useful ornamental landscape tree.

The pink trumpet tree requires full sunlight to part shade and grows to approximately 25-feet in height in Southern California.  The non-aggressive rooting system makes it a good choice for use in smaller confined planter areas such as a parkway strip.  It performs well in the urban environment.  Like most trees, it prefers well drained fertile soils however I see this tree flourishing under less than ideal conditions.  No noted pests or disease, hardy to 24º F, damaged below 18º F.  After spring flowering, it grows a green to brown colored pod.

A close relative to the pink trumpet tree but faster growing

A close relative to the pink trumpet tree but faster growing.  By M.Ritter, W. Mark, J. Reimer, C. Stubler

Unlike the pink trumpet tree, the closely relate golden trumpet tree is a more rapid, larger growing tree.  It too is deciduous, and like the pink trumpet, it flowers in the spring with an impressive display of brilliant, fragrant yellow trumpet flowers.

This tree grows to a larger size than the pink trumpet, up to 50-feet tall and similar width.  It has a spreading, low canopy that matures into a broad, round-headed or vase shaped crown.  It prefers full sun to part shade.

Branch strength is rated as medium to somewhat weak and root growth is more aggressive than the pink trumpet.  Unlike the pink trumpet, the golden trumpet tree should not be used in a confined planter are.

Both these trees perform well in our mediterranean climate and their different growth characteristics allow for varied use,  one in more confined areas, the other requires more room to grow.  Once established, both are relatively drought tolerant.

Hope you find this helpful, let me know if you have any questions!

 

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Worried About Your Tree?

We have gone from record drought to record amounts of snow and rain throughout California.  While the winter storms have wreaked havoc on our infra-structure (Oroville dam spillway, flooding in San Jose, etc, they have been a blessing for drought starved trees throughout the west.  Years of inadequate rainfall reduced soil moisture leading to an incredible dieback of trees numbering over tens of millions within the state.

The urban environment creates stresses not normally encountered in the wild.  In cities and suburbs, trees contend with confined planter area, compacted soils, improper or inadequate irrigation, poor maintenance practices, improper pruning, shading by homes or buildings.   Stresses created by the urban environment reduce tree life expectancy, sometimes by as much as 50%.

During the drought, I have seen an increase in tree failure, whether a limb drop or whole tree failure.  In most instances, crown, limbs, branch and twig dieback were the obvious symptoms of the drought.  Many times, clients mistakenly thought the dieback was caused by disease or insect, however root dieback from minimal soil moisture was the cause of crown dieback.

Now, with the heavy rainfall and wind, tree failure due to saturated soils are on the increase.  Trees remain upright due to their root system.  Structural and buttress roots grow outward from the trunk at the (root crown), out to the edge of the crown (known as the dripline).  At the dripline, the structural roots are 1-2″ in diameter.  They continue to grow outward, branching into the small, fine feeder roots that absorb moisture and nutrients.  Depending on local conditions, tree roots may extend 1.5 times the tree crown diameter.  Based on San Diego soil conditions, most roots grow within the upper three feet, typically 80% of the roots are within the top 18-24″ of the soil.

Roots in dry soil are held in place by friction.  However, when rain saturates the ground, it acts as a lubricant, lessening the soil friction holding roots in place.  When wind combines with excess weight from rain or snow, the energy is transmitted down the trunk to the roots.  Soil root friction reduced by saturation causes roots to loose anchorage, resulting in a failure.  When roots fail to support the tree, it is assessed as a root failure.  When the entire root ball rotates up from the soil, it is a soil failure.

Homeowners with large trees in close proximity to their property should examine their trees for any change in condition as a warning sign of a potential problem.  Changes to be aware of include:

  • Is the tree leaning?
  • Are there soil cracks at the base of the tree?
  • Is the soil lifting, tilting or rippling at the tree base?
  • Are there dead limbs or branches in the crown?
  • Is there a progression of twig, branch and limb dieback?
  • Did the tree drop it’s leaves abnormally early?
  • Did the tree not leaf out as in the past?
  • Any obvious open cavities, cracks or splits?
  • Any animals or insects nesting within a hollow, cavity or crack?
  • Any fluids, abnormal sap flow or other discharges from the tree?
  • Has irrigation been reduced or eliminated to the tree?
  • Has there been construction activity near the tree?
  • Have the roots been disturbed by any nearby utility or sidewalk work?
  • Is the tree sitting in water, is there proper drainage?
  • Has there been a change in grade near the tree?

If you can say yes to any of the above, your tree may have acquired defects that increase the risk of failure.  The increased risk of failure may result in property damage or personal injury to your family, friends, or any pedestrian near the tree.  A tree with a history of previous failures possesses an increased risk of failing.  Trees may not present any obvious signs or symptoms of a defect.  Unseen decay may exist within a limb or trunk, or as a root rot.

Whether commercial or residential property, if you are concerned about the health and safety of your trees, you should contact an arborist certified by the International Society of Arboriculture, (ISA).  Once certified, the ISA allows arborists to enroll in specialized training to earn the credential of a Tree Risk Assessor Qualified.  While anyone may attempt to assess the health and structural integrity of a tree, certified arborists who are qualified in tree risk assessment represent the industry standard and best management practice for tree risk assessment.

Tree risk assessment is the current best management practice to determine tree risk of failure associated with defects.  The assessment utilizes a level two basic visual assessment and a two page ISA format for the assessment protocol.  The assessor may determine more advanced assessment techniques are required, however usually a basic visual assessment will suffice.

If you have noticed a change in the health or condition of your tree, take proactive measures before a catastrophic accident, call a certified arborist knowledgeable in tree risk assessment.

Click here to read an article published in the LA Times Risk Assessment article.

Reducing Irrigation During the Drought? Don’t Forget Your Trees!

I have been getting an increased number of calls from people concerned about their tree(s) starting to dieback. They want a certified or registered consulting arborist to evaluate the tree health condition, determine the cause of the tree decline, and recommend treatment options or removal.

For the past two to three years, I have noticed the increasing number of declining trees throughout San Diego. Especially noticeable is the tree dieback in the backcountry as well as local canyons and open spaces. Even drought tolerant Eucalyptus, Oak and Pines trees are struggling to survive.

The cause of our tree decline and dieback is the ongoing California drought. With yet another year of little winter rain, soils throughout San Diego county have little moisture reserve remaining. The drought is affecting native as well as ornamental trees used in the landscape.

Indeed, certain trees in our area are struggling due to insect infestation. The gold spotted oak borer attacking Coast Live Oak, as well as a host of ornamentals including Olive and Liquidambar trees have been infected with fusarium vascular disease introduced from borer and insect infestations. Therefore, it is not uncommon for most people to assume their tree must be declining due to some kind of insect or disease.

I have observed people rarely consider the effect of the drought as being the primary cause for tree decline. The tree living in the back yard or slope area for the past several decades may be dying simply because there is no more water in the soil profile!  Even the deepest rooted trees cannot survive accumulated years of consecutive drought.

I recently received a call from a gentleman complaining his fifty year old Jacaranda tree was dying. The new foliage had germinated then died back, now small twigs and branches were dropping. The bark on the trunk was exhibiting uncharacteristic roughening. The tree was located at the bottom of a slope near a turf area. Months ago, the turf sprinklers had been turned off, now the tree was struggling to survive.

Tree roots seeking moisture grow well beyond the drip line of the tree crown. Under drought conditions, soil moisture is not being recharged from winter rains. Unless a tree is receiving supplemental irrigation, it is reliant upon finding soil moisture by growing into irrigated turf and planter areas.

With increased water restrictions and rates, people are reducing or eliminating irrigation to their lawns and shrub beds without considering the effect on nearby trees. Trees that adapted their root systems to getting water from nearby irrigated areas that no longer get watered will begin to decline as the remaining soil moisture is exhausted.

A tree weakened by drought becomes increasingly susceptible to secondary pest or disease infestations. Many beetles can detect stressed trees from miles away. However, attempts to eradicate secondary insect infestations will not resolve the underlying cause of the tree decline.

So, if you notice your tree starting to decline, here is a brief check list of considerations:

-Is the tree irrigated or non-irrigated?
-If non-irrigated, does the tree get water from a nearby irrigated source?
-Has there been recent re-programming or turning off the irrigation?
-Any recent construction or trenching nearby the tree?
-Any grade change such as fill soils placed over the tree roots or cuts?

A well maintained, mature street tree in the front yard of a property may add an additional 7% to the assessed value of a property, a dead or declining tree obviously reduces street appeal and real estate value.  Trees can be retained and successfully survive the ongoing drought, contact a certified or registered consulting arborist to provide a tree health evaluation and recommendations on how to protect your tree investment value.