What is wrong with the picture above?
 
A few days ago, I decided to start writing about some of the “landscape no-no’s” that I see when I am doing landscape consults.
From time to time, I will focus on a particular “landscape no-no” and its solution.
My hope is that it will help you to avoid or fix these problems.
My first “landscape no-no” post, featured the photo above.  Readers were invited to figure out what was wrong and leave a comment.
Quite a few of you left comments, correctly identifying the problem.
But, for those of you who aren’t sure what is wrong with the tree above – look closely at the drip emitter….
The problem is that the emitter is too close to the trunk of the tree.
Initially, when trees are first planted, it is a good place for the drip emitter to be.  The roots are primarily near the trunk.
However, as a tree grows, so do its roots.  The single emitter next to the trunk of a mature tree, isn’t doing it any good.
The roots grow outward and their ends are concentrated where the branches end.
The reason for this is that when rain falls, the majority of it drips off the ends of branches – so that is where roots tend to grow out to.
So, if your tree and emitter(s) look like the photo above; how can you ‘fix’ it?
As your tree grows, you need to add more emitters, equally spaced around your tree.  They should be located where the tree canopy (branches) end. (I do recommend burying your drip line – it looks better 🙂
Below, is a photo of a large tree and I have drawn in recommended emitter placement…
You can see the emitters are widely spaced around the tree and are located where the tree canopy ends.  As your tree grows, you need to continue to move the emitters outward.
The Arizona Municipal Water Users Association has a great, free publication that guides homeowners through landscape watering, including recommended watering schedules….
The diagram above, from “Landscape Watering By the Numbers” shows recommended emitter placement along with how deeply trees should be watered.
It’s important to note that trees do not need to be watered as often as your other plants.  But, they do need to be watered more deeply – 3 feet.  
(Here is a link for how often to water your trees and other plants if you live in the greater Phoenix metro area).
**If you don’t have a separate irrigation line for your trees, you can periodically deep water your tree by turning your hose onto a slow trickle and let it slowly soak into the soil.  Move the hose until the entire outer canopy of your tree has been watered.  
 So, do you have this “landscape no-no” in your garden?  Don’t worry – now you know how to fix it 🙂

**Stay tuned for our next “landscape no-no” soon!** 
To receive your own copy of “Landscape Watering By the Numbers”
simply click the link above.  You can also view it online.  Note – this publication is written for residents of the greater Phoenix area, but the information is very helpful to anyone who lives in a hot and dry climate. 
As I began my trek through the desert, I found beautiful specimens of cacti, plants and even some wildlife, but I also found a few skeletons as well…..
   
Mature Saguaro

This beautiful Saguaro was one of the first cacti that greeted me on my walk.

The first skeleton I came across was from a Saguaro cactus; part of it still standing upright.  You can see where top part of the skeleton has fallen to the ground.

Here it is close up.  The decay is till present as you can see inside.  The woody remains of the saguaro are called ‘ribs’ and are what supports the Saguaro cactus.

Above, is a photo of a Saguaro that had just fallen.  You can easily see the ribs.  Whenever a Saguaro cactus would fall in a landscape setting, we would move it to an out of the way area where it could decay.  Then we would take the ribs and put them back into the landscape as a display.  Saguaro ribs are considered a beautiful accent in the desert landscape and are prized by many.

Native Americans used Saguaro ‘ribs’ to build roofs, walls and even furniture.  Another use was that they would make long poles that they used to knock off the Saguaro fruit, which is edible.

Saguaro are not the only types of cacti that leave behind skeletons….

 
Teddy Bear Cholla (Opuntia bigelovii)

 Teddy Bear Cholla (above), also has an interesting skeleton.

 

Above, is a photo of a segment of Teddy Bear Cholla that is in the process of decaying.  You can see the woody skeleton starting to show.

Cholla skeletons are sometimes used as walking sticks.  Artisans also use cholla skeletons to make southwestern forms of art.

It is illegal to remove Saguaro and Cholla skeletons from the desert, unless you have permission from the owner.  Specimens can sometimes be purchased at certain plant nurseries that specialize in cacti.

So do as I do…..enjoy them out in the desert and take lots of photos.

As I was walking along a desert nature trail, I came upon this unusual feature.  To be honest, I was surprised by its presence.  But then I got to thinking, don’t live things, or those things that were formerly alive belong in a garden?

What do you think it is?  Need some clues?  Here are the first ones:

I was once part of a beautiful semi-tropical forest near the equator…

My current location is quite a ways north of the equator, although I never left the land I origin from…

I was buried in layers of mud until I was unearthed…
I am much heavier now then when I died…
I used to be alive, but that was a long, long time ago…

Volcanoes, wind, and water helped to create what I am today…

When I was young, I was soft enough to be able to be cut with a knife but am now harder than steel…

Much of my color comes from iron…

You can find me in many different areas of the world, (Denmark, Mexico, China, New Zealand, and Indonesia), my home has always been in the land that makes up Arizona…

Parts of me are stolen every year by tourists…

 

Have you figured it out?

Here is the answer…

Did you guess correctly?  These pieces of petrified wood are made up of the remains of trees that are approximately 200 – 250 million years old.  They are no longer made up of any living material.  They are now made completely of stone.  The semi-tropical forest where they once stood in, has since disappeared.

Over 200 million years ago, Arizona was close to the equator, and the climate was much more humid, hence the presence of a sub-tropical forest that the trees originated from, before being transformed into petrified wood.

I came upon these beautiful specimens while I was walking along the Nature Walk, which is located next to the Mayo Clinic in Scottsdale, Arizona.  These specimens were brought here from the Petrified Forest National Park, which is in north-eastern Arizona in the Painted Desert.

More information about petrified wood and their origins can be found here at Petrified Forest National Park.

What comes to mind when you think of cactus?  

Perhaps the first thing you think of is the spines. If you have ever been unfortunate enough to have been pricked by a cactus, you’ll likely never forget that most of them have needles.  
*Did I ever tell you about the time I worked on golf course landscape and backed into a teddy bear cholla and got an entire piece lodged in the back of my leg?
 
Besides being painful to those who get too near to cacti, did you know that there are important reasons that cacti have spines?

Golden barrel cactuses (Echinocactus grusonii)

First, let’s look at the spines of cactus for what they are – the main part of cactus often functions as a modified stem, and its needles are the leaves.
 
The most obvious function of cactus spines is to protect the cacti from animals and people. There are, however, a few animals who aren’t deterred by the sharp spines of cacti such as javelina, tortoises and pack rats.

Saguaro cactus (Carnegiea gigantea) spines

 
Suprise, the primary function of the spines are to actually shade the cactus.
 
Although just one small spine would hardly provide shade, thousands of them can provide enough.
 

Why is sun protection needed for the surface of cacti? The shade from the spines let the cactus lose water through the atmosphere. This helps keep the cactus temperature relatively low.

Black-spine prickly pear (Opuntia macrocentra)

 Another function that the spines serve is that they help certain species of cacti such as cholla to root and spread.

Teddy bear cholla (Opuntia bigelovii)

Spines of the Cholla are specialized to detach and attach onto anything that comes to close. There are tiny barbs at the tips which grab on to anything that gets too close. It almost appears as if they ‘jump’ off of the main cactus as they latch on the unlucky recipient.

Segments of the Cholla are usually moved and then fall off and grow in better conditions. If you have ever seen cholla growing in large groups, this is why. 
**If like me, you are ever unlucky enough to find a piece of cholla embedded in your clothes or worse, your skin – you can use a comb to help pull out the barbs.  When hiking in the desert, it is easy to get them stuck on your shoes.  I usually grab a rock and use it to push off the Cholla segment.  When all else fails, a good pair of needle-nose pliers works.
 

Two young saguaro cactuses are emerging from the shelter of a creosote shrub.

Hopefully, you have a new appreciation for cacti and their spines.  But, it’s still important to be careful because it hurts when you get pricked!
Young saguaro cactus were peeking out from its bursage nurse plant.

As you walk through the desert, there are many opportunities to view some of the striking cacti and their unique shapes.  What is not initially apparent, are the many examples of plants helping young cacti survive.  However, if you look closely, it is all around you – desert shrubs and trees sheltering growing cacti from the harsh desert climate. 

Young barrel cactus underneath a bursage nurse plant
Despite their tough, prickly appearance, cactus are quite vulnerable.  Of the thousands of seeds that are released by each cactus, only a tiny fraction grow into new cactus plants.  Most would not survive if it were not for “nurse plants.”   These plants provide much-needed protection from the sun, cold temperatures and predators (including humans).  Nurse plants also provide much needed additional moisture for the new cacti.

Mammillaria microcarpa 

It is easy to walk by and not even notice the presence of the small cacti growing underneath nurse plants.  Most of the year, the fishhook cactus (Mammillaria microcarpa), pictured above, are almost impossible to see.  It is only in the spring when they are blooming that you can spot them.

Hedgehog cactus outgrowing it’s bursage nurse plant.

For the smaller cacti species, bursage (Ambrosia deltoidea) most often serves as the nurse plant.  It also often serves as the first nurse plant for saguaro cacti.

 
Two young saguaro cacti outgrowing their creosote and bursage nurse plants
 
Creosote (Larrea tridentata), palo verde, mesquite or ironwood trees often serve as the nurse plants for larger species of cacti.  As it grows larger, it requires more water and nutrients from the soil, which leaves little for the nurse plant.  So frequently, the nurse plant will decline and die as you can see from the photo above.

Young buckhorn cholla emerging from its bursage nurse plant.    

So next time you have the opportunity to take a walk in the desert, look around….you will most likely see examples of this unique relationship of plants helping young cactus survive.

Blue Palo Verde (Parkinsonia florida)

When people think of the Sonoran desert, hillsides studded with saguaro cactus and cholla often come to mind.   But interspersed between the cactus, you will find the iconic palo verde trees with their beautiful green trunks and branches.

The word “Palo Verde” means “green stick” in Spanish, referring to their green trunk, which is a survival mechanism in response to drought.  
 
Palo verde trees are “drought deciduous,” which means that they will drop their leaves in response to a drought situation.  Their green trunks and branches can carry on photosynthesis, even in the absence of leaves. 

‘Desert Museum’ Palo Verde (Parkinsonia hybrid ‘Desert Museum’)

Palo verde trees act as a “nurse plant” to young saguaro cacti by protecting them from the cold in the winter and from the intense sun in the summer.  Beautiful, yellow flowers are the product in the spring.    

  ‘Desert Museum’ Flower
There are three species of palo verde that are native to the desert Southwest; blue palo verde (Parkinsonia florida), formerly (Cercidium floridum), foothill palo verde (Parkinsonia microphylla), formerly (Cercidium microphyllum) and ‘desert museum’ palo verde (Parkinsonia x ‘Desert Museum’)
 

Another species of palo verde that is prevalent in the landscape are called palo brea (Parkinsonia praecox), formerly (Cercidium praecox).  They have a dusty green trunk and branches that twist and turn.  Their cold hardiness range is around 15 to 20 degrees F.

Palo Brea
PALO VERDE USES: Palo verde trees serve as beautiful specimen trees where their green trunks, branch structure, and flowers serve as an attractive focal point in the landscape.  They are drought tolerant, once established and provide lovely filtered shade year-round.  
 
When deciding where to place your tree, be sure to take into account that they need a lot of room to grow, mature sizes are listed below.  
 
Palo Verdes don’t do well when planted in grass and will decline over time.  Locate away from swimming pools due to flower litter in the spring.
Because of their more massive thorns and branching tendency to point downwards, palo brea trees aren’t recommended in areas close to foot traffic.  
  
Mature Sizes:
Blue Palo Verde – 30 ft x 30 ft
‘Desert Museum’ Palo Verde – 30 ft high x 40 ft wide
Palo Brea – 30 ft x 25 ft
Foothills Palo Verde – 20 ft x 20 ft
As with many desert trees, Palo Verde trees have thorns, except for the ‘Desert Museum’ Palo Verde.  

Foothills Palo Verde
PALO VERDE MAINTENANCE:  Prune to elevate the canopy and maintain good structure.  Avoid hedging and “topping” trees as this stimulates excess, weak growth.
 
MY FAVORITE: As a landscape manager, horticulturist and arborist, I have grown and maintained all of the palo verde species mentioned, and I truly enjoy them all.  However, at home, I have 4 ‘Desert Museum’ trees.  In comparison to the other species, their trunks are a deeper green; they produce larger flowers, are thornless and grow very quickly in the desert.  Also, they require little, if any, tree staking when planted. 
‘Double Delight’

In the Desert Southwest, we are blessed with two different blooming seasons – spring and again in fall.  

While two bloom seasons is generally one more than many regions experience, roses don’t enjoy the heat of summer and go into summer dormancy.  That means that they just exist and don’t grow or bloom significantly. Their leaves may show signs of sunburn.

 
‘Medallion’

However, once September arrives and the days begin to grow shorter and temperatures begin to cool, it is time to lightly prune your rose bushes, which will stimulate new growth. 

Begin by pruning back 1/4 of the top growth, removing sunburned foliage and any flowers present.  

As always, prune back to an outward facing bud at an angle of 45 degrees.  Seal any pruning cuts larger than the diameter of a pencil with Elmer’s glue to prevent borers.

Fall is also time to fertilize roses in preparation for their fall bloom season.  Apply an organic fertilizer formulated for roses.  Afterward, be sure to water in well.

 
‘Abraham Darby’

**For those that want to go the extra step, I would recommend soil amendments such as compost and manure in addition to rose fertilizer, which results in greater growth, lush foliage and blooms over the long term.  

To do this, first make 4 – 5, six-inch deep holes around each rose, placing them at least 1 ft. from the center (I use the end of a broom handle for this).  Then apply a mixture of aged steer manure and alfalfa pellets (rabbit food) and pour into each hole.  Water in well.  

The aged manure improves the soil structure and slowly releases nutrients.  The alfalfa pellets release a type of alcohol as they break down that roses just love.

By lightly pruning and fertilizing in early fall, you’ll enjoy a fall filled with beautiful roses.

 

In the past, people have asked me how long does a saguaro cactus arm take to grow back. The commonly held belief is that it takes 100 years before they will develop an arm.

However, as with much plant information, this answer is not always correct, it actually takes less time for a saguaro cactus to grow its arm back in a landscape setting than it’s native habitat.  

The most critical factor in determining the timing of when a saguaro will start to grow an arm is the availability of water. Put simply, the more water a saguaro receives, the more quickly it grows. In a landscape setting where irrigation is present, a saguaro will grow much more rapidly then they do in their natural desert habitat. Saguaro cacti that grow in southern Arizona (near Tucson) grow more quickly than those in the western areas of the Sonoran desert because there is more rainfall in southern Arizona. 

A saguaro growing in its native habitat can take 50 – 100 years to grow arms. In a landscape setting, arms often appear much earlier.