Saturday, June 30, 2012

July Plant Information Class Will Be on the 11th at 1:30

Hey everybody just a reminder,  my plant information class held usually on the first Wednesday of the month,  will be held this month on the second Tuesday, July 11th at the usual time; 1:30 pm. This class is going to cover cactus and succulents. We're going to look at the major types of cactus and succulents (selected families and genus) and talk a little bit about strategies for developing a cactus and succulent garden like the ones you see at the Arboretum and the Huntington.  As always we're going to look at some of the most interesting, entertaining, and even strange plant information questions that the plant information volunteers and myself have fielded over the last month. I'm also going to be talking about a new pest, the 'shot hole borer'. This is an interesting pest that has already killed and damaged trees here in the San Gabriel valley.  you don't want to miss this meeting. Lastly,  it's hot, so were going to be, as usual, in the well air-conditioned plant information headquarters located in the library building here at the Arboretum. See you there!

Wednesday, June 13, 2012

One Messed Up Mulberry

A gentleman brought in a Mulberry (Morus alba) shoot from a tree that was having problems. The new foliage was distorted and seemed to wilt over the course of one to two months. According to him the onset was sudden and no other nearby trees (this was the only mulberry) seemed to have the problem. We ruled out a gas leak and upon viewing the shoot under magnification no insects or insect debris were noted.
Distorted Mulberry Shoot
After ruling out insects and diseases the last thing left was to investigate physiological (nutrition, salt burn, etc.) causes and finally, herbicides. Going through the list the only description I found that matched the damage to the shoot was that for 'phenoxy' herbicides (the giveaway was the curly-queue stems). One of the most common scenarios where this type of herbicide damages trees and shrubs is when 'weed and feed' lawn fertilizer is applied to the lawn under the canopy of a sensitive tree. The owner of the damaged tree however did not apply any of this kind of fertilizer on the lawn under the tree. Another cause of this kind of damage is a disgruntled neighbor spaying an herbicide intentionally on the tree, but the tree owner denied having any tiffs or feuds with fellow neighbors. 

So the most likely cause of this damage to his tree was a neighbors spraying accident. 'Phenoxy' type herbicides (those containing 2-4 D and similar compounds) are notorious for causing damage to trees from spray drift caused by applicator error or applying the spray in windy, hot conditions. All it would take would be a neighbor spritzing weeds in his lawn with a hose end, pump, or hand pump sprayer in a light breeze; and to top it off Mulberries are notoriously sensitive to these types of herbicides. 

The treatment? If the accidental dose is not to great the tree should grow out of the damage either before the summer or next spring when the tree re-leafs after its winter dormant period.

Saturday, June 2, 2012

This Wednesdays Plant Information Class -Tree Donor Tour - Plumeria Question

This Wednesday's Plant Information Class

This Wednesday, June the 6th Plant Information Class will be held in my office at 1:30. The topic will be about plant allergies and how to design a landscapes for those of us who dread spring for the pollen firing squad it is. I will also be introducing all plant information volunteers in attendance to an exciting new project that should get us all published.

Tree Donor Tour

I was honored to be a co-presenter on today's Tree Donor tour. We had about 50 people take the tour which gave an overview of the horrendous damage that occured as a result of the December 1st windstorm. In all we lost over 245 trees and 26 days of operation due to the storm. Arboretum Director Richard Schulhof, Superintendent Tim Phillips, Senior Biologist Jim Henrich, and myself hosted the 90 minute tour which also covered some of the new collections we'll be initiating as a result of the wave of donations recieved and the art exhibit curated by Leigh Adams that uses wood from the felled trees as the material for art created just for  the exhibit.  Here's a video 

The Damage

The tour covered the vast magnitude of the damage to the Arboretum and why some trees failed and others didn't. One of my favorites (in terms of examples of preventable tree failure) is the 150+ year Blue gum that failed as the result of the damage the tree suffered when a metal conduit was installed next to it in the 1960's. Other interesting tidbits were the decapitation of palm trees by the flailing limbs of the huge cypress trees next to them and the inability of large, tropical ficus to stand up to the wind.  

The Recovery

Right after the windstorm large areas of the Arboretum were inaccessible to vehicles, so the first thing that had to be done was road clearance. County fire crews and other county crews were invaluable for this. Brush clearance crews from parks, public works, agricultural commissioner's office and other county department personal came to our aid immediately after the storm. Call me a sentimentalist but it really struck my heart how these crews all seemed motivated by a feeling of admiration for the Arboretum. These guys were really motivated to get the Arboretum open again so that people could enjoy this place. Now all this enthusiasm and sentiment was great, but  the real stars, in my opinion, were Tim Phillips and Jim Henrich who both were able to steer the extremely enthusiastic crews in the right direction and ensure that the more sensitive parts of the L.A. Arboretum's collections were not compromised by that enthusiasm. 
One of the strategies Tim put in place that really helped keep the clean up from being more damaging than the windstorm was to make sure only Arboretum crews worked in sensitive areas. This included most of the road-inaccessible parts of the collection and the Tropical Forest area. 

Another incredible and heartening result of the disaster was the outpouring of support from the Arboretum from the public. We had hundreds of phone calls, emails and inquiries wondering what that individual could do for the Arboretum. That's when we started the tree fund; since then the fund has accumulated over $70,000 in donations. 

New Collections Started, Old Collections Renewed

Besides the tree fund one positive result of the storm has been an invigoration of our collections programs on several fronts.

Seed Acquisitions  

Jim Henrich has been acquiring seeds from index seminum (seed index)  lists from various botanic gardens around the world with concentrated focus on:

  • Australian Plants
    • Will probably focus on trees and shrubs that are less messy, less fire-prone, and flower more than previous Arboretum acquisitions as well as flowering perennials, both herbaceous and bulbs. 
  • South African Plants
    • The Southern California-like climate of the South of Africa and the Cape of Good Hope area will continue to be a source of acquisition for non-invasive specimens for our collection. 
  • South American Plants
    • With special emphasis on Chilean, Argentinian, Brazilian and Peruvian plants from climate zones similar to ours. One tree in particular that we hope to increase our collection of; the genus Tabebuia a south and central American flowering tree that has quite spectacular blooms and shows great potential as street tree here in L.A. County. 

Engelmann Oak Grove

The Arboretum's Engelmann oak grove is the northernmost pure stand of a remnant oak population that spanned an area from northern Mexico up into Arizona and over to the coast of southern California. In that the stand is unique and that part of the trees range has been shrinking due to development it is an ecological treasure. Jim Henrich has started a program that will help to ensure that this treasure is available for generations to come. Ever the Arboretum was started in 1948 very few oak seedlings have established in the Grove located on the south side of Talac Knoll. This is because the fires necessary for oak establishment, and the dominance of invasive non-native grasses, coupled with the use of string trimmers by contract maintenance crews, have combined along with a large population of seed and seedling eating ground squirrels to keep establishment of Engelmann oak seedlings to a next to nothing level. In the last two years Jim Henrich's oak establishment program has lead to an increase in survival in these seedlings which you can see if you go up to the grove on the Knoll and observe the number of chicken wire encased seedlings that are now growing there. For more information pick up a copy of the 2012 early spring edition of Pacific Horticulture in which Jim details the Arboretum's oak conservation efforts. 

Erythrina Collection

One of the hardest hit trees in the Arboretum were the coral trees, genus Erythrina. As a result it is one of the collections that will be greatly expanded here. In 1966 the city of Los Angeles made Erythrina the official city tree but did not specify a species because it was thought that between the many species of the genus that there would be a greater flexibility in cultural conditions for the many micro-climates of Los Angeles.  Already we have planted E. corraloides  in the spot where several E. crista-galli were first burned from the bad frost of two years back and then decimated by the windstorm. On Tallac knoll where frost is not much of a problem new plantings of Erythrinas including E. speciosa have been installed. 

Art from Disaster

Leigh Adams is curating an exhibit scheduled mark the anniversery of the windstorm. Over 70 artists have selected wood from storm-felled Arboretum trees and tree limbs to fashion into artworks that they will later donate back to the Arboretum for the exhibit and to raise funds through the artworks sale. 

Plumerias from Cuttings

Q. My friend wants to plant Plumerias from cuttings now by cutting them and placing them in water; can she?

A. Although now isn’t a bad time to take Plumeria cuttings, it’s just not the best; the best time is when they are just starting to leaf out in the spring. If you decide to root them now they should be about 8-12 inches in length. Make a clean cut with a sharp knife and disinfect the knife between cuts (very important) the best way is to dip the knife in grain alcohol and flame it with a propane torch until all the alcohol burns off. The second best way is to use a 10% Chlorox solution (hard on the knife; make sure you wash and DW-40 the knife before you put it away). After you make the cuttings take off all of the leaves and flower buds and store them in a cool dry place for at least two weeks to allow the cut end of the stem to heal over. This is very important if you don’t want to see your Plumeria cuttings deflate like punctured balloons after they are planted. After they are healed dip the bottom of the cutting in water and then rooting powder before planting it about 3-4 inches deep in the potting soil in 1 gallon containers (this should be cactus mix; there is also a method of using pea gravel to stabilize the cuttings shown on the first link below. Put your potted Plumerias in at least half day sun (they need heat to root). Water your Plumeria cutting only once until you see new growth, then water regularly. Check out the video, as the author talks about using dark rocks as a mulch to warm up the soil to encourage rooting.  
However, if your friend insists on placing freshly cut Plumeria shoots in water she runs a good chance of brewing a batch of rotten Plumeria tea. 

This site talks about planting the cuttings.

This video talks about the healing process and demonstrates how to root the cuttings. Also talks about using dark rock mulch and when to water the cuttings. Very good video: