A Miner Problem

The first call of the morning today was a request to bring in a leaf for a diagnosis of a disease on a citrus tree. I asked the caller what the situation was and they said that their citrus trees had what their neighbor called “Minor Disease”. They went on to explain how the new leaves of their citrus trees were curling and disfigured. I suggested that they send me some pictures of the problem first. Below is what I received from them:

Leafminer damage on citrus leaves (red arrows point to leafminer galleries). 

Citrus leaf miner (which is an insect and not a disease) affects the new growth of citrus. Control is mostly cultural. Avoid pruning citrus at all more than once a year. Do not feed citrus in the summer of fall, when leafminer is most active, instead feed your trees in the late winter or early spring. Feed mature trees only once a year ½ of what the label says. By keeping new growth to a minimum you can control the leaf minor because it only infests new leaf growth. Eventually over time natural predators will effect some control over the leaf miner, and it will become a low level pest on your trees.

If your citrus tree is young and just establishing levels of leafminer damage can be quite dramatic. You can remove the disfigured leaves, although doing so can harm the growth of the tree if the removal is extensive. If your tree is a sapling however, you need to control the leaf miner without removing the leaves as doing so could stunt the young tree’s growth. You could monitor for the flying moth that lays the leafminer eggs on your trees leaves and spray either Neem oil or a Spinosad containing insecticide on the leaves when the moths show up in a trap (a trap specific for citrus leafminer) . You can purchase these traps at your local full service garden center or, order them online.

UC Davis page on Integrated Pest Management of citrus leaf miner

Mentioned above (these are examples and are not recommendations)

Traps 1 2 3

Spinosad product examples 1 2

Neem oil product examples 1 2

Fall Color Still Peaking

Here at the Arboretum we have a fall color season. It's not a punctuated, Rose Parade season like the east coast or the Sierras gets where all the trees that turn color do so in a blazing display of overwhelming reds, oranges, yellows and hot pinks (the color of dogwoods when they turn), instead ours is a lazy, slow moving parade put together by the local chamber of commerce where one float after another slowly rolls by, separated by marching bands blooming trees and aloes. 

Crepe myrtle tree with red fall foliage. 

Yellow fall foliage on these Crepe myrtles. 

Wisteria vine turning color as it drapes over bamboo plants. 

California native grapevine; a brilliant red performer in the fall as it drapes over 60 foot tall palms. 

Various fall color trees in the Meadowbrook section. 

Ginkgo biloba 'Canopy'

Carpet of spent leaves under Ginkgo biloba 'Canopy'

Ginkgo biloba 'Saratoga' in the herb garden. 

Ginkgo biloba 'Cleveland'

Chinaberry tree in the foreground, Ginkgo biloba 'Cleveland' in the background.

Formosan Sweet Gum, Liquidambar taiwanensis

Putrid Plummeting Pomegranates Puzzle Patron

I just had an email inquiry that included the following:

"I have a very sick pomegranate tree that is dropping yellow leaves all over the place and producing few fruits, all of which are rotten and eventually dropping. Also, there are black spots on many of the leaves.

I've attached a photo of the tree to show you what is going on and would be eternally grateful if you could - via this photo, if possible  - provide a diagnosis and suggest a cure.  I believe this tree is 90 years old, and I'd love to preserve it if I can."

Pomegranate tree in question.  

As you can see the tree looks fairly healthy, although the fence seem to have shaded the tree's lower half, causing any leaves that might form their to appear chlorotic. I puzzled over this photo trying to find something wrong, then I saw something and blew up the photo to find out what it was.

Obvious animal damage to fruit. 

It was animal damage, most probably rats. As you can see in the upper photo the Pomegranate bush grows along a fence that most probably is providing access to the fruits for the rats.

The solution? Mine would be not to grow fruit, however this is not what I think the person making the inquiry would want. If you have a rat problem like this the key to control is to restrict the rats access to the fruit tree or bush. In this case I would trim the thing so that the no part of the tree is closer than 1 foot from any part of the fence. Also make sure the tree is not 1 foot or closer to any utility lines, if it is, trim it, unless the utility lines are power lines, then call your utility company to trim it for you as trimming trees near power lines is extremely hazardous.

As far as the black spots go, I cannot see any in the photograph, so I will have to wait until the patron brings in some leaves.

Something Bad is Happening to Our Magnolias, But There May Be Some Hope

In the last several years I've noticed that many Southern magnolias (Magnolia grandifloras) in the greater Los Angeles area are taking a turn for the worse. They're losing branches, their canopies are thinning and they are, in general, looking terrible. For example below is a picture of a southern magnolia cultivar 'Samuel Sommers' in 2012 (on the left) and just recently (on the right). Notice in the recent photo that only 50-60% of the trees canopy is left. The side-by-side photo below is one of the milder examples of how Southern magnolias have declined over the past several years.

Magnolia "Samuel Sommers" left: in 2012, right November 2018

Below also are some examples of Magnolia grandiflora street trees growing in an Alhambra neighborhood (there is nothing special about Alhambra except that they seem to have a large amount of M. grandiflora planted as street trees).

Magnolia grandiflora planted as street trees in Alhambra California

Magnolia grandiflora planted as street trees in Alhambra California. Notice the dead branches appearing randomly in the canopy of the tree, a process called 'flagging'. 

These Magnolia grandiflora trees once had much larger canopies, with some of the trees canopies shrinking to 1/2 their previous size.

What's causing these once beautiful, magnificent trees to decline? There doesn't seem to be any one cause, but there are many culprits. The number one culprit is that this tree is like a fish out of water here. Native to the deep south and south eastern portions of the United States, Magnolia grandiflora thrives in cool, but not snow covered winters and hot, humid, and rain punctuated summers that its native range provides. It does do well here it it has plenty of humidity and water, however these conditions are becoming harder to maintain. But climatic differences aren't the only culprit.

Magnolia grandiflora suffers from a significant pest and two very damaging diseases. The pest is the polyphagous shot hole borer (PSHB), for which Magnolia grandiflora is a host.  The diseases are Xylella and Botryosphaeria 

But most of the damage to Magnolia grandiflora and many other street trees can be attributed to what is essentially a very bad interpretation of a famous landscape designer's radical new idea. Frederick Law Olmsted, who previously had designed Central Park on Manhattan Island, New York, was commissioned to design one of the first planned suburbs in the United States, Riverside Illinois. His plan specified walkways and trees lining the avenues of the community. These became so popular that the idea of tree lined urban and small town streets became an archetype of America and a specification of many an urban plan. Unfortunately this vast majority of these Law Olmsted imitators did not specify the same amount of space between street and sidewalk as Law Olmsted -10 feet between the two, ample room for the the roots of most trees.

The planting of trees in spaces much smaller than the almost 300 square feet than Law Olmsted gave the Riverside trees lead to an entire nation with millions of trees stressed out. The idea of tree lined streets took off, but the idea that those trees required adequate space to set out their roots did not.  And although smaller trees like Privets and Crepe Myrtles can be planted in the small spaces between urban and suburban streets and sidewalks, larger trees planted in such small spaces are basically doomed.

So though there may not be hope for the thousands of Magnolia grandiflora planted as street trees here in the Southland, there may be some hope for the tree if it is planted with plenty of room (and regular watering) to let it grow. In fact just behind the two waning Magnolia grandifloras located just west of the Crescent garden here is a compact variety of the tree that seems to be thriving, Magnolia grandiflora 'Victoria'. Although there is a small amount of shoot dieback on the tree it is relatively healthy. The reason? I'm not completely sure, however the tree is surrounded by other trees and is next to a lawn, this would mean plenty of water and humidity. But the one thing I think is making a big difference is that the tree is free and clear of lawn or any other kind of plant underneath its canopy and the only thing there is a thick layer of its own leaves. I can't tell you the number of times I've observed evergreen trees doing better because a thick mulch of their own leaves was permitted to remain underneath their canopies.

Magnolia grandiflora 'Victoria'
Notice that the canopy of this tree is healthy and thick compared to the Magnolias pictured above. 

Closeup of Magnolia grandiflora 'Victoria'  

Substantial mulch layer under the canopy of Magnolia grandiflora 'Victoria' composed of its own leaves.  

The mulch layer of leaves is at least 3-4 inches deep. 

October 24th, 2018

Got out at 8:00 am for a walk around the Arboretum. Here's some of the things I saw. Below are some mushrooms located near Ayres Hall. These are most probably some sort of Agaricus. Agaricus bisporus is the common table or 'button' mushroom, but this one smelled kind of like chlorine or phenol, so it's probably Agaricus xanthodermus, a mushroom that, if you are able to get past the hideous smell that gets worse when you cook it, can cause projectile vomiting and diarrhea in a percentage of the people who eat it. 

In the South African section, just north, northwest of the Kiosk, I found this flower, probably a Crinum hybrid. It is one off the last things blooming in this section which just a week or two ago was dotted with dozens and dozens of white and pink Amaryllis blooms.

Located just east of the 'Roots and Shoots' building is this Ceiba speciosa. It's just listed on our database as a generic Chorisia speciosa (the old name for Ceiba speciosa).

After taking a pic of the Floss silk tree I started down the dirt road that wanders around the western edge of the Arboretum. This path winds you through the Chinese-North American tree collection which is where, if you are going to be looking for fall color here, you want to be.

Right now there isn't much color, but about a week ago we had about a 1/2 inch or more of colder rain and that usually starts the color change. If all goes well and we don't have too many heat waves between now and then, mid-November should be a good time to come to see the start of our fall leaf-color season.

The Chinese-North American collection. 

This is probably the least travelled part of the Arboretum but it can be the most beautiful at times. It is densely forested with trees like Quercus alba, the white oak native to North America, Zelkova serrata from China, a relative of Ulmus parvifolia the Chinese elm that turns an orange burgundy in the fall, and Toxicodendron succedaneum, one of the plants used to produce lacquer in southeast asia and wax in Japan. A word of caution, the substance contained in just about all parts of Toxicodendron succedaneum is urushiol, the active ingredient in poison oak and poison ivy, both close relatives of this plant.

Toxicodendron succedaneum (pic taken mid-November 2015)

Here is a compilation of fall color photos taken at various times here at the Arboretum over the last several years. 

Ceiba speciosa with carpet of dropped petals coating the ground beneath. 

A tree can have two 'shadows'; one from the light and one from it's petals, falling to the ground. There are particularly fine displays of petal carpets going on now thanks to the efforts of this and other Ceiba speciosa trees that dot the Arboretum.

Left: Pampas grass, Right: Mexican sage. 

The morning haze was particularly photogenic this morning as is evidenced by this shot next to the Queen Anne cottage.

Nothing completes this picture of gentility more than a great big red dragon skimming your lake as you sip Arnold Palmers and listen to the peacocks wail.

On closer inspection you see the lantern team putting some final touches on big red.

On the road going from the Hugo Reid adobe to the Bauer lawn, a panda tries to catch some zzzz's; however the panda's family seems to looks on in displeasure at their horizontal deportment.

The Ceiba speciosa on the gateway fountain lawn are just about all in bloom -there salute to the Dodgers winning the pennant, now if they could only develop a blue flowered version of this tree.

And finally, the peacocks have received an honor long in coming - a shrine devoted solely to them. What has amazed me about this huge and spectacularly colored lantern is that it did not budge an inch during the recent windstorms here -a credit to the solid and beautiful workmanship of the company that has built them. I am amazed at the beauty of these lanterns, so I hope, if you are reading this, you buy a ticket and enjoy the show.

Botany Boot Camp Links and Things

Thank you everybody who attended Botany Boot Camp! We had a great class and I was inspired by your enthusiasm!
Here is the link to the Plant ID blog that I was talking about. 

October Plant Information Class Notes

Grand Park Landscaping Photos

Shrub Selection

●       Reality Check

●       Function

○       Barrier

○       Fill

○       Diversion

○       Loiter Prevention

○       Erosion Control

○       Edge Softening

○       Utility Hiding

○       Neighbor Hiding

●       Water Use

○       Know your landscapes hydrozones.

○       Water saving vs. fire resistant

○       Drainage needs

○       pH needs

○       Function

●       Temperature requirements

○       Deciduous?

●       Growth Habit & Size

○       Know ultimate height and width

○       Root “invasiveness”

○       Density

○       Axillary growth potential

●       Texture

○       Hard to smooth

○       Spikey to soft

●       Color

○       Hot to Cool

■       Color can move you (literally)

●       Flowers  & Mess

○       Flower color (see above)

○       Flower size

○       Bloom period

○       Flower “mess”

●       Container Size

○       Large vs. Small

●       Planting

●       Staking

○       Proper staking

●       Pruning

○       Look up each plant

■       Some plants can take a shear

■       Other need to have their growing tips pinched

■       Pines and candles

●       Irrigating

○       In general ½ or less of the ET index.

●       Planting for fire areas.

●       Some selected shrubs

○       Juniper

○       Podocarpus

○       Syzygium

○       Ficus?

○       Raphiolepis

○       Box hedge

○       Hopseed Bushes

○       Dwarf myrtle

○       Pittosporums

○       Xylosma

○       Abelia

○       Ligustrum

○       Nandina

○       Melaleuca (was Callistemon)

○       Dwarf Abelia

○       Westringia

○       Agapanthus

○       Morea and Dietes

○       Plumbago

○       Berberis 'Ken Hartman' Hybrid (Oregon Grape)

○       Ceanothus 'Joyce Coulter' (Joyce Coulter Ceanothus)

○       Heteromeles arbutifolia (Toyon)

○       Mahonia pinnata (California Barberry)

○       Rhamnus californica (California Coffeeberry)

○       Others

            

L.A. Arboretum Lantern Festival Set Up

Here is a video I took of some of the lanterns that will be featured at the Moonlight Forest Lantern Festival at the L.A. Arboretum.  Enjoy! PS, the music stops at about 3 minutes, however feel free to hum a rousing soundtrack as you watch the spectacular display go by.

Celebration and Demonstration Garden Tour

Cantilevered patio in the old Sunset Demonstration Garden (photo by William Chrisman Aplin). 

Back in 1959 the L. A. Arboretum opened a landscape demonstration garden in conjunction with Sunset magazine.   Located just behind the administration building, it contained small, packaged idea gardens that helped inspire do-it-yourself homeowners. Here are some color photos of the garden taken in the 60's and 70's by William Chrisman Aplin, a photographer who worked for Sunset Magazine. It was designed with the help of some fairly well known landscape designers, including Edward Huntsman-Trout.

The Courtyard Garden in the demonstration garden, designed by Nick Williams. 

In 1998 Sunset Magazine funded a re-do of the Demonstration Garden. It was not so much an idea garden for do-it-yourselfers as it was a collection of well designed garden vignettes. It featured designs by several well known landscape designers.  Although Sunset Magazine no longer sponsors the garden (it has been renamed the 'Celebration Garden' and is used for parties and weddings, including the wedding of yours truly), it is still a beautiful destination and inspiration for both do-it-yourself gardeners and landscape designers.  One of the more compelling areas in the garden is the Meditation Garden designed by the late well known local garden designer Lew Watanabe. It features a weeping wall, a granite fountain that is comprised of rough granite blocks with a thin film of running water gently cascading down them.

Lew Watanabe's weeping wall fountain.

Take The Tour Here

Groundcover Lecture Notes

• Groundcovers and Lawns Origins
• The hungry hunter gatherer
• Lawns represent prey nearby
• Groundcover may represent food plants
• Flowers represent fertility and water
• Lawns
• Also represent cattle and horse ownership
• A cattle and horse owner looks out and sees the grass cut by the grazing of their animals.
• Pasturage and Golf have propelled the lawn industry
• Golf was first developed in China around AD 400
• Lawn ownership and maintenance could be a form of:
• Exercise in Dominance of territory (master of all you see with a weapon in hand to defend it), and target sport (warrior culture).
• Increase in sight lines for security
• Lawn Pros
• Highly attractive, prestigious
• Cool down the areas they are planted in.
• Unequalled for athletic play
• Huge subconscious satisfaction.
• Lawn Cons
• Huge amount of water
• Require regular maintenance
• Gas powered mowers are highly polluting.
• Most of Southern California is naturally averse to lawns
• Increased humidity
• Types of Lawns
• Summer dormant
• Fescue
• High water use but not as much as other summer dormant
• Clumping
• Susceptible to ‘melting out’
• Aerate or Dethatch every several years.
• Creeping red -California native good for shade
• Bluegrass
• High water use
• Fine texture
• Shallow roots -can dry out inland readily.
• Disease susceptible
• Bentgrass
• Very high maintenance -putting green
• Requires lots of water.
• UC Verde Buffalo Grass
• Winter and Summer dormant
• Slow growing
• Only really does well in the inland valleys.
• Grows too slow on the coast.
• Rye
• Excellent regenerative properties.
• Great for heavy use, athletic fields
• Requires regular watering
• Winter dormant
• Bermuda
• Low growing varieties make good putting greens
• Fine textured
• Go dormant in the winter: turf colorant best used as overseeding can be patchy
• Best with regular dethatching
• Dethatch in June here
• Uses ½ the water that Fescue does.
• St. Augustine
• Luxuriant, old fashioned look
• Less watering than fescue, more than bermuda
• Needs dethatching once every 2-5 years
• Dethatch in June, not Fall. Overseeding with rye not the best idea, instead consider turf colorant when it goes dormant.
• You can prevent dormancy by applying high nitrogen in the late fall before it goes dormant, however you have to water more frequently.
• Zoysia
• Marketed as miracle grass on the back of newspaper Sunday circulars.
• Long dormancy period makes it problematic for this area.
• Paspalum
• Great for salty conditions near the seashore; also for Palm Springs lawns.
• Cool season dormancy almost as long as Zoysia, slow growing.
• Kikuyu
• The ‘Surrender’ lawn
• Does not wear as well as bermuda, but can look just like it.
• Lawn like groundcovers
• Dichondra
• Impossible to keep nowadays as the herbicide that allowed it to exist without hours of weekly weeding is off the market.
• Still a great shade groundcover, as is its native cousin, Dichondra californica.
• Related to yams and morning glories.
• Kurapia (Phyla nodiflora cult. “Kurrapia”
• A sterile, low growing cultivar of  once popular water-saving California native ground cover Lippia nodiflora: Kurrapia can be grown and even mowed as a relatively low growing lawn AND purchased in easy to install rolls like sod.
• Dymondia marguerite
• Tough grey-green low growing groundcover for full sun.
• Initial prep and establishment are important: dig amendment in to 8-12 inches deep.so the plant can develop deep roots.
• After about 1-2 years of establishment you can cut the watering down gradually to once every two weeks.
• Will take some traffic after established -however limit events and parties to once or twice a year -do not play football or ball sports on your Dymondia lawn.    
• Specialty Mixes
• Eco lawn
• Patch Mixes
• Shade mixes
• Native grasses
• Bouteloua
• Festuca californica
• Carex (praegracilis and tumulicola
• Groundcovers
• Perception that bare ground is infertile, sterile.
• Fear of erosion
• The concept of ground cover is relatively recent and may have been fueled by the Dust Bowls of the 1930’s.
• Modern reasons for ground covers
• Aesthetics, ground-cover provides a green area of continuity between larger landscape elements and plants.
• Erosion control
• Can prevent hillsides from sliding down if root structure is sufficient.
• Must balance erosion control and fire prevention.
• Some plants might actually increase breakdown of bedrock.
• Always consult a soils geologist if there is a question of hillside failure
• Security
• Perceptively maintained and/or planted areas of landscape make people feel more secure.
• Sightlines created by low groundcovers increase security.
• Groundcover drawbacks
• Water need is more than just bare ground.
• Increased humidity.
• Vermin and pests
• Rats and Ivy
• Midges and Red Apple
• Discourage ground nesting bees.
• Many require maintenance
• Trimming
• Cutting back
• Fertilization
• Thinning
• Some can cause hillsides to come down.
• Iceplant
• Sedum
• Selected Groundcovers
• Iceplants
• Aptenia (Red and Pink Apple)
• Drosanthemum floribundum
• Delosperma
• Lampranthus
• Sedum etc.
• Sedum species
• Asphodelaceae
• Aloe ‘Red Riding Hood’
• Creeping Aloes
• Asteraceae
• Gazania
• Osteospermum
• Dymondia
• Achillea
• Rosaceae
• ‘Pink Carpet’ Roses
• Other low growing roses
• Lamiaceae
• Rosemary
• Salvia
• Ajuga
• Lippia
• Kurapia (see above)
• Thyme
• Sage
• Rhamnaceae
• Cotoneaster
• Ceanothus
• Berberidaceae
• Nandina
• N. purpurea, N domestica dwarf (shade and sun)
• Berberis repens (shade)
• Ophiopogon japonicus nanus