Category: hot gardens

Should you get gardening advice from an A.I.?

You’ve probably already heard about ChatGPT, the new artificial intelligence program by OpenAI that is being called “scarily good.” Well, okay, I thought, maybe it is scarily good about techy stuff but how good is it with gardening advice? So I asked it this fairly basic question.

chlorosis shrub leaves

What causes plant leaves to turn yellow with green veins?

Here is what ChatGPT answered:

“Leaves on plants that turn yellow with green veins is a condition known as chlorosis. Chlorosis is caused by a lack of chlorophyll, which is the pigment that gives leaves their green color. The green veins on the leaves indicate that the plant is still producing some chlorophyll, but not enough to fully color the leaves.”

Okay — so far so good, I thought. And it continued…

“There are several causes of chlorosis, including:

  1. Nutrient deficiencies: A lack of iron, manganese, zinc, or other essential nutrients can cause chlorosis. This is often due to a lack of these nutrients in the soil, or a pH imbalance that makes it difficult for the plant to absorb them.
  2. Disease: Some plant diseases can cause chlorosis, such as leaf spot or rust.
  3. Pest infestations: Pests such as spider mites or aphids can suck the sap from the leaves, causing them to turn yellow.
  4. Environmental factors: Extreme heat, cold, or drought can stress plants and cause chlorosis.”

Item 2 is where ChatGPT begins to slip off the track. Leaf spot or rust do not look remotely like chlorosis; they are orangy yellow round spots on leaves not yellow leaves with green veins. Spider mites and aphids can damage plants but the effect is also spotty leaves–smaller spots–not leaves yellowing.

Then Chat GPT goes for the solution:

“To fix this issue, you need to find the root cause of the problem and take appropriate action. A soil test can help you determine the pH and nutrient levels in your soil and make recommendations for correcting any imbalances. You can also consult with a local nursery or botanical garden for help identifying and treating any diseases or pests that may be affecting your plants.”

That’s where ChatGPT ends.

My conclusion is that it offers basically good advice–as I did in an earlier post about yellowing leaves. But it falls short of the detailed information I wrote about, including short term, fast fixes to out-of-season yellowing leaves. ChatGPT clearly hedges its bet by suggesting that one should consult with a real local human being. (Or maybe a Master Gardener!)

Is ChatGPT trustworthy?

OpenAI, the company that developed this A.I. warns not to trust what ChatGPT says completely — that it sometimes just makes things up. This is a failing of other artificial intelligence programs, too. My guess is that it doesn’t want to appear ignorant — which, of course, opens the question about whether an artificial intelligence computer program can behave as if it is embarrassed by a lack of knowledge — but that is for another blog. Not this one.

I have another gardening question for ChatGPT — one that should be more challenging, but, unfortunately, the Open AI website is so busy that I haven’t been able to get on it again. I’ll report about it, if I can talk with it again.

Our 8 most popular newsletters

  1. Best and beautiful native shrubs for extreme heat
  2. Five fragrant plants for your garden
  3. Where to get free or cheap trees for your garden
  4. Six distinctively different landscapes to replace a lawn
  5. Cover up that naked wall
  6. Nine trees to combat climate change
  7. Four desert trees good for soil, 4 toxic ones
  8. Plants that bloom even in mid-summer scorching heat

Where to get free or cheap trees in L.A., Phoenix, San Diego and…

The push for increased tree planting in cities around the world swells with each disruptive weather event. Whether it is reflected in nation-drowning floods in Pakistan or wildfires sweeping mountainsides bare in California, climate change has arrived. And ordinary people are saying: “We gotta do something.”

In response to clamor from citizens to “do something”, several U.S. Southwest city mayors have begun to set goals for the number of trees that should be planted in their communities. And they have enlisted the aid of organizations–usually utility companies–to help them by offering free or discounted small trees.

Before I go into how to get free trees locally, however, I want to answer a basic question.

Why plant trees?

Tree planting in cities has gone on for decades, mostly for aesthetic reasons. People like living and walking along tree-lined streets. There are now two other reasons to plant a tree at your home.

A street lined with Palo Verde trees that bloom brilliant yellow in April.
  1. As I wrote in the previous post, trees can become green canopies, natural umbrellas to cool hot city streets, sidewalks and other hardscape. It is a simple mechanical process: tree leaves blocking, reflecting or minimizing sunlight means cooler air and a cooler landscape underneath.
  2. There is also a chemical process that occurs when a new tree is planted. As they grow, trees absorb carbon dioxide, a gas that is a major contributor to climate change. Trees are carbon capturing plants that remove CO2 from the air and keep it stored in their leaves, trunk and branches. Less CO2 slows climate change. And the oxygen plants emit is the breath of life for people like you and me.

Trees planted for both these reasons make the world a pleasanter place for humans.

Ok. Now for those free trees

In Los Angeles, the Green New Deal identifies a goal of planting 90,000 trees. To reach that goal an organization called City Plants will deliver up to 7 free trees to your door. You have to plant them yourself but they provide instructions.

Crape myrtle

Don’t have space for another tree? They will also plant a street tree in front of your home or business, including obtaining the proper city permits.

City Plants also offers many “Adopt a tree” events for same day pick up of one fruit or shade tree. Check their website for details.

So who is picking up the tab for all this? The LA Dept. of Water and Power.

In Phoenix the goal is to plant 5,000 trees every year to increase the citywide tree canopy to 25%. It’s currently around 10%. Working in conjunction with Salt River Power and Trees Matter, Phoenix residents can take home 2 free desert native trees — mesquites, palos verdes, desert willows–after attending a Zoom meeting about planting and caring for trees. This program is underway for 2023.

San Diego is going in a different direction: homeowners receive a $35 rebate from San Diego Gas and Electric for each tree purchased up to a total of 5 annually. And–happy news for renters and condo owners–you don’t have to plant the tree in the ground. Put your 1 or 5 gallon starter tree in a big pot on your balcony or patio and you qualify for the rebate.

Chines pistache tree hot gardens

In Tucson, the goal is an ambitious Million Trees planted by 2030. Trees for Tucson, a part of the environmental organization, Tucson Clean and Beautiful, is selling locally grown trees for $30 each. You will have to plant the tree yourself.

A better tree deal comes from Tucson Electic Power. You can order up to 3 starter trees through their website for $5 each. They will send you an email about where and when to pick up your tree to take home and plant.

Like San Diego, Albuquerque uses a rebate program to help homeowners plant new trees. The ABQ Tree-Bate plan will pay a homeowner 25% of tree planting costs up to $100 as a rebate on the water bill. Better yet, the rebate can cover tree maintenance expenses and irrigation installation as well as the tree you plant from the city’s authorized list. Be sure to check the website before you rush out to buy a new tree.

And San Antonio, which really isn’t in a desert but I’m including it anyway, gives away free fruit trees at various special events around the city. (If you want more info about growing fruit trees in the desert go here.)

memoir writing guide ebook paperback

Big goals but not involving homeowners

El Paso also has a goal of a Million Trees planted, but is working through a non-profit organization which solicits cash donations and does the planting itself. I couldn’t find anything about free or almost free trees for homeowners.

Another example of a non-profit soliticiting donations and doing the planting is Las Vegas where the mayor wants the city to plant more than 60,000 street trees by 2050 to provide shade and bring temperatures down in areas most impacted by the urban heat island effect. Nothing on the website about tree planting assistance for homeowners.

Now about those huge national and international tree planting organisations

I am suspicious of some of the organizations who will for a dollar or two or more promise to plant a tree on your behalf somewhere around the country or around the world. You may not be helping who you think you are. Some are commercial tree growers who plan to harvest the “tree you paid to have planted” in 15 to 30 years. “Your tree” may well become a roll of bathroom tissue! These people are not restoring permanent forests!

Our 8 most popular newsletters

  1. Best and beautiful native shrubs for extreme heat
  2. Five fragrant plants for your garden
  3. Where to get free or cheap trees for your garden
  4. Six distinctively different landscapes to replace a lawn
  5. Cover up that naked wall
  6. Nine trees to combat climate change
  7. Four desert trees good for soil, 4 toxic ones
  8. Plants that bloom even in mid-summer scorching heat

Visit my author’s site to see the books I’ve published.

Winterproofing palms to survive climate change

You have probably already seen one: a tall palm tree wrapped in strips of burlap which the owners hope will protect the tree during winter cold. In truth, this burlap bandage going from the ground to where the fronds begin is unlikely to have any impact at all.

There is, however, a proven way to “weatherproof” and protect palm trees in areas where winter temperatures sometimes fall below freezing–places like Palm Springs, Tucson, Las Vegas and London. That’s right–palm trees are now being planted and thriving in London in the U.K., a city that is further north than Seattle.

Climate change is definitely having an impact on gardens worldwide and on which plants will thrive where. While we think of palms as warm climate trees, they are now being planted in areas where cold, freezing winters are normal. And future changes in weather conditions are becoming more unpredictable, except that it looks like extremes of hot and cold will become normal.

The Proven Way to Protect Palms

So here is how to look at the situation: The best way–the proven way–to winterproof palm trees, which thrive in warm to hot weather, is to start off right and plant one of the palms that are also hardy–one that has built-in DNA resistance to winter chill. And you may be surprised at how many palm trees fit this requirement.

Mediterranean Fan palm for identification purposes
This Mediterranean Fan Palm (Chamerops humilis) in Las Vegas is shrub-like – not tall and stately.

Let’s start with my London friend’s palm tree which she was told by her local garden center was a “New Zealand palm”. I recognized immediately that New Zealand had nothing to do with it. Her palm was and is a sturdy, hardy multi-trunk Mediterranean Fan Palm (Chamerops humilis).

Ideal for small gardens, this short shrub-like palm has survived brief cold spells down to zero F. (-18 C.) And “brief” is the important factor; their survival depends on daytime warming after a night of chill. It has been 14 years since she planted it in a sheltered corner and, growing slowly, it still survives, and recently has even bloomed and produced fruit.

The next on this list of chilly-weather survivors is the Date Palm (Phoenix dactylifera), a native of the Middle East. It’s the tree you probably think of when someone says “palm tree”. Tall with long pinnate (rather than fan-like) fronds, this 75 foot high giant is very hardy. It has been known to survive and regrow after experiencing temperatures down to 5 F. (-16C.) Dates are, obviously, edible and the difficult-to-find Bahri dates are the very best. Unlike the chewy Medjool dates you buy in a store, Bahri dates are soft, delicious and taste like caramel.

Next is the Date Palm’s cousin, the Canary Island Palm, (Phoenix canariensis). While a few of these palms have reached a mature height of over 130 feet, that is uncommon. But they still are among the tallest palms. It will withstand temperatures to 20 F. (-7 C.) at least for a short time.  After a cold snap the fronds will turn brown and may very slowly regrow.

Tall palm trees native to the West

More common in gardens here in the West are two fan palm trees. The California and Mexican Fan Palms, (Washingtonia filifera and W. robusta), natives of Southwestern U.S. and northern Mexico, are also rugged, surviving cold weather as low as 18 F. (-8 C.)

Trimming the “hula skirt” of dead fronds off these trees may make them look a bit more tidy but that “skirt” offers the palms some protection, some insulation from severe weather. The downside of not removing dead fronds is that Mother Nature may do it for you during our fierce Spring and Fall windstorms. And falling palm fronds are very dangerous. The thorns on these fan fronds are also hazardous.

Like the date palms, the Washingtonias can reach heights of 60 to 100 feet, making them not particularly suitable for residential gardens although we see them planted around homes everywhere. After a few years’ growth they are more like architectural columns in a yard than trees.

Shorter palms for home gardens

A native of Mexico’s rocky Guadalupe Island, the Guadalupe Fan Palm (Brajea edulis) is a distinctive palm with a smooth grayish-brown trunk and silvery fronds. It grows about a foot a year to a mature height of only 25 feet tall, ideal for a residential garden. It flowers in summer from long drooping stems and the blooms are fragrant. Because it is a native to a small island with variable weather conditions, it tolerates heat, wind and drought, and it is one of the hardier palms, to 18 degrees F. (-7.7 C)

Pindo Palm (Butia capitata) , a native of dry South American savannahs, is another short palm, growing only to 20 feet. In Florida where it is popular in home gardens, it is known as the Jelly palm because people make jelly with its fruit. It tolerates temps as low as 5°F (-15 C) In this photo a very young Pindo palm was planted at the same time as the Washingtonia behind it. They have very different growth rates.

Originally found in high altitudes in China, Japan, Myanmar and India, the Windmill Palm (Trachycarpus fortunei) is a semi-dwarf palm with windmill-shaped fronds. Slow-growing to 15 feet tall, this tree loves our summer heat but will withstand winter temperatures of -10F (-23C).

My favorite fails the chill test

My favorite is the graceful Queen Palm (Syagrus romanzoffiana) a native of South America commonly planted in Southern California. It does not do well at all in cold weather. While I’ve seen it planted in hot dry Palm Springs, but with the weather uncertainty stemming from climate change, it may not survive there at all, except in a local micro-climate. Nearer the California coast, it grows beautifully and is ideal for home gardens.

And finally…

If a freeze comes and your palm tree ends up with browned fronds, do NOT remove it right away. Give it a few weeks or even a month or two of Springtime weather and it may very well produce green fronds again. And if you have to replace it in the end, choose one of the palms on this list.

Our 8 most popular newsletters

  1. Best and beautiful native shrubs for extreme heat
  2. Five fragrant plants for your garden
  3. Where to get free or cheap trees for your garden
  4. Six distinctively different landscapes to replace a lawn
  5. Cover up that naked wall
  6. Nine trees to combat climate change
  7. Four desert trees good for soil, 4 toxic ones
  8. Plants that bloom even in mid-summer scorching heat

Is it an attractive weed, a native plant or tasty edible?

Rather than giving you gardening advice for March today I’m going to tell you about one plant, which turned out to be more interesting than expected.

Moving from one desert, the Mojave, to another, the Sonoran, has meant that I am learning to identify many new native plants, among them, the Common Mallow (Malva neglecta). The name “neglecta” is so apt because my neglect has resulted in massive growth of this plant in a narrow yard beside my house.

Surprise! Not a native

Yesterday afternoon, after I wrote the headline for this post and the paragraph above, I discovered that while this variety of Mallow is as common as dirt here in Southern Arizona it is not a native at all. Not even a native plant of the Western Hemisphere. It’s origins are in Egypt, probably in Nile marshes. That makes sense because the leaves are so large and dark green which is very untypical of desert plants, for example, the Desert Mallow (Sphaeralcea ambigua).

mallow plants growing wild

Since like most of you I am home all the time because of COVID-19, I tentatively planned to start removing at least some of this mallow mini-field.

But after learning more I’m not sure what to do about it. If anything.

How to eliminate weeds 3 ways–or not

Should I listen to the Round-up folks who claim to make it easy to exterminate with a quick spray? (We all know about Round-up so I won’t write more about this option.)

Or how about going extreme like some here in Arizona and blowtorch the weeds–uh…the mallow? You read that right: some gardeners here use flaming blowtorches on weeds because that will kill the seeds, too, even ones that are under a layer of gravel. No blowtorch among my garden tools, so that eliminates this one.

Then came the suggestion of a third way for weed elimination. A couple of gardeners recommended mixing 55% vinegar with water and a dash of liquid soap, then spraying it on the weeds. I am tempted to test this idea–someday when I feel I can risk using the vinegar in my emergency pantry for something other than salad dressing.

The next option is re-wilding

Inspired by a British gardening movement to let wild native plants thrive along roadsides and in city squares, should I simply let my Mallow continue to grow? In the U.K. a Back-to-Natives trend is growing (pun intended!) in an effort to support other native species, including bees, badgers and other wildlife. I wonder if here in Arizona, rattlesnakes and scorpions may find the mallow mini-field a friendly habitat.

Or should follow the advice of two forager friends who pick leaves of dandelions and mallows for their salads?

Behold the multi-use vegetable

mallow blossoms and seeds

They have assured me Mallow is edible, that its seeds tastes like its cousin, Okra (Abelmoschus esculentus).

“Use it in a salad or cook it to thicken soups like gumbo,” they tell me.

Then they go on to add: “It’s really high in Vitamins A, B, and C as well as calcium, magnesium and potassium. Like kale.”

Like kale?

No thanks. (And please don’t reply with a list of all the health benefits of kale. Broccoli, which I love, also is vitamin-packed.)

This morning I was informed by yet another Arizona gardener of one more use for Common Mallow’s big, soft leaves: as toilet paper! Eureka! That’s the solution to the hoarding problem. Plant Mallow now and have a lifetime supply of t.p.

And if the coronavirus situation and the hoarding get worse, maybe I’ll start picking the Mallow leaves and selling them on a street corner as a multi-purpose vegetable for kitchen and bathroom.
Respect the weeds. Stay safe. Happy Gardening.

Our 8 most popular newsletters

  1. Best and beautiful native shrubs for extreme heat
  2. Five fragrant plants for your garden
  3. Where to get free or cheap trees for your garden
  4. Six distinctively different landscapes to replace a lawn
  5. Cover up that naked wall
  6. Nine trees to combat climate change
  7. Four desert trees good for soil, 4 toxic ones
  8. Plants that bloom even in mid-summer scorching heat

Composting is an unnatural act…

Well, composting is unnatural in a hot dry climate where plants produce small leaves with waxy or oily exteriors, where grassy lawns are few and far between and where the air is, more often than not, dry as a bone.

Those are things that are antithetical to the natural composting that occurs in cooler, more forested zones where big leaves and/or lots of pine needles, weekly grass clippings from the lawn, and damp air make composting a normal part of the environment and is fairly easy for a gardener to do.

So because it is not a natural function in a hot dry climate, I’ve never written about it.

During this last month, however, I received an question about it so if you want to start composting, even though you are living in a hot dry climate, here is some advice.

First: the good news about compost. Compost is food for the soil. It loosens the soil hardened by heat and dry air and makes it easier for plant roots to grow deep. It enriches the earth with long-lasting nutrients. Used as a mulch on flower beds it can be protective.

But compost should not be used in place of fertilizer. Its carbon to nitrogen ratio is too unstable, too unpredictable to count on as a fertilizer. In fact, if the compost process isn’t fully complete, the compost may suck nitrogen right out of your soil. Compost that is “complete” is crumbly, not smelly, dark brown or almost black and will, very gradually over years, release some nutrients to your plants and help balance the pH in your garden.

composting food waste

Now to get started the first thing you are going to need is a place or a container to hold the garden and kitchen waste you want to turn into compost.

From left: beginning, middle and done with composting!

When I had a compost heap in my Santa Barbara garden, it was just that, a heap of grass clippings and leaves in the far corner of my backyard that had been started by the previous owner. If I was doing it again, I would have either set up attractive wooden bins or put everything into metal canisters that could be turned. (Live and learn!)

Then begin by adding biodegradable stuff, such as grass clippings, leaves, coffee grounds, sawdust, faded flowers, dead annuals, and even newspapers torn up into little bits. You need a mix of one part green stuff to 3 parts brown stuff for the best composting process. For green stuff you add things like grass clippings; brown stuff are things like chopped straw or old dead dry leaves.

Next, toss in a shovel or two of your native soil to jump-start the process. NO need to buy compost bacteria or fungi starter. Your native soil has what you need.

And dampen the whole thing. Don’t soak it. Just keep it damp like a sponge that has been wrung out. This is especially important in our dry climates. You may have to dampen it daily…or more often. If possible, keep your compost in the shade so it won’t dry out as quickly.

Be sure to turn it regularly so the decomposing process continues on all materials, not just those on outside. When you turn it you may discover it is warm or hot in the center. The center of the compost bin may heat up to 130F, which should kill all the wild seeds that ended in it. If it becomes too hot, that is a sign of excess carbon and you should add more green stuff, like grass clippings or weeds you pulled from your garden.

raccoon by wall

Now about food waste. If you are composting in a container, especially a revolving one up off the ground, toss in all the food waste you have. BUT, if your compost “bin” is actually a compost heap you may find wild raccoons and other hungry animals visiting it. They love those old apple cores, orange peels, rotting pumpkins, bananas and other food leftovers.

Do NOT put meat or dairy in your compost pile. It will not decompose quickly, will smell hideous and may attract vermin or dangerous bacteria to your garden. Also avoid leaves of oleander, they are poisonous. And avoid adding eucalyptus and salt cedar leaves.

I strongly recommend acquiring some type of plastic or metal compost bin. Some cities offer residents free compost bins, so call your local government to see if you can get one or two for free. There are also several on Amazon that look good, including a pink compost bin. One even claims to be able to make compost in two weeks! That’s fast! Composting usually takes months. Happy composting!

Our 8 most popular newsletters

  1. Best and beautiful native shrubs for extreme heat
  2. Five fragrant plants for your garden
  3. Where to get free or cheap trees for your garden
  4. Six distinctively different landscapes to replace a lawn
  5. Cover up that naked wall
  6. Nine trees to combat climate change
  7. Four desert trees good for soil, 4 toxic ones
  8. Plants that bloom even in mid-summer scorching heat

Ask Me Anything and tree planting deception

Sorry, but “Ask Me Anything” has been canceled because there have been too many trolls.

In my Hot Gardens newsletter in the winter of 2006 I suggested that my online gardening friends do just 2 things for the new year: 1) plant a tree and 2) change one lightbulb to LED.

Rio Grande Fax Tex Ash autumn
The large Fan Tex Ash tree thrives i hot dry climates and has gorgeous golden leaves in Fall.

Asking people to change light bulbs seems terribly out of date now–everyone has already done it.
But planting a tree in your own garden is as smart and timely now as it was then. Especially since many ads about tree planting around the world and the U.S. are, as I have recently learned, somewhat misleading.

Deceptive ads about tree planting

We’ve all seen the ads telling us that Nepal or Ethiopia or some other country or a mega-international company has planted millions of trees.

And those claims of tree-planting are true and so inspirational!

But the ads tell only part of the story. As it turns out, some uncounted number of these millions of trees are being planted in ‘tree plantations’ and will be harvested in 10 to 20 years.

In a tree plantation there is no attempt to restore a natural forest which is more complicated than just sticking little trees in the ground lined up in neat rows. Trees in a plantation create a monoculture, rather than a diversified ecosystem. Each tree is like the next one all spaced for optimum growth with no smaller trees or shrubs in between. That means in 10 to 20 years when these more mature trees are cut down and hauled away the benefits of the trees will revert back to zero. Tree plantations are a short-term fix to a long term problem of rapidly increasing carbon dioxide in the air and climate change.

Crape myrtle Lagerstroemia indica hot pink
When most other plants are wearing summer green, the Crape myrtle bursts into colorful bloom. In dry climates it is a relatively small tree.

So I urge you to plant a tree or a few trees or long-lived shrubs in your garden in 2020. Become part of a long-term solution.

Happy gardening in 2020!

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  2. Five fragrant plants for your garden
  3. Four trees good for soil; four toxic ones
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The bee-friendly Tucson Botanical Garden

The Tucson Botanical Garden has become very bee friendly. Yes, of course there are still displays of cacti and other desert plants as well as their famous ramadas and winding shady paths. Their efforts to support bees, however, are non-traditional for a Botanical Garden and should be applauded. And, in my opinion, should be emulated by other public gardens!

Here are some of the efforts they are making:

solitary bee homes Tucson Botanical Garden

Above, what appear to be tall, whimsical garden ornaments are actually homes for solitary bees–the kind of bees that do not live in hives and do not produce honey–but pollinate flowers and fruits and vegetables nonetheless. These bees are non-aggressive because they do not have hives or honey to protect.

As you can see these homes are holes drilled into the wood. It is something so simple almost any gardener could do it. Or you can purchase an economical bee home online and easily hang it up on any branch in your garden.

What to do about honey bees

Bee trap in tree Tucson Botanical Garden

Working in conjunction with a local Tucson beekeeper, this box up in the tree is a bee trap — not a bee house. When a swarm of honey bees has entered the box, the beekeeper comes and removes it to transfer the bees to his apiary because honey bees can become aggressive. The bee trap in the tree is then replaced with an empty one.

flowers to attract bees at Tucson Botanical Garden

The Tucson Botanical Garden is noted for its shade-producing ramadas in several designs. Beside this one is a bed of flowers to help provide food for bees. Not to mention the flowers are visually appealing.

Mediterranean herb garden Tucson Botsnical Garden

One of my favorite places in the garden is the Mediterranean herb garden under its blue pergola. It was one of the first gardens created in 1964 by the plant collector Harrison Yocum who founded the Tucson Botanical Garden at his home. Since then the garden has been expanded with purchases of neighboring properties.

And here are some other photos of the garden, including the docent who gave me a private tour. Thank you, Carolyn.

colorful ramadas at Tucson Botanical garden

As I was leaving I discovered this amazing decorative wall by a local Tucson artist. No bees that I could spy but there are hummingbirds, red peppers, butterflies and magical angels. If anyone knows the name of the artist, please let me know.

Decorative wall Tucaon Botanical Garden

Just a reminder. Until the daily high temperature falls below 90 F (32 Celsius) the only thing your garden plants need is regular watering. It’s inadvisable to fertilize or transplant during hot summer months.

Our 8 most popular newsletters

  1. Best and beautiful native shrubs for extreme heat
  2. Five fragrant plants for your garden
  3. Where to get free or cheap trees for your garden
  4. Six distinctively different landscapes to replace a lawn
  5. Cover up that naked wall
  6. Nine trees to combat climate change
  7. Four desert trees good for soil, 4 toxic ones
  8. Plants that bloom even in mid-summer scorching heat

The dirty truth about yellowing leaves when Fall hasn’t even arrived

chlorosis shrub leaves

It is a subtle change but one day you notice that the leaves on one of your shrubs (or maybe a tree) are turning yellowish and as far as you know yellow leaves are not natural to this plant–even in Fall. You look closer and see that the veins in the leaves are still green as you can see in this photo.

Well, what you are looking at is chlorosis, a kind of iron-deficiency in plants that inhibits the development of chlorophyll, the stuff that makes green plants green and keeps them alive and growing.  It is most common in plants grown in alkaline soils with high pH.

The problem begins in the dirt, the soil in your garden.  Even in hot dry desert-like gardens there is ample iron in the soil, but unfortunately plants can’t access it. The technical causes for the iron/soil problems read like a chemistry textbook so I will skip it, but advise you to take steps to reverse the condition before it gets worse. After all, you don’t want to lose an expensive plant or tree, especially to a plant problem that is curable.

What you need to do at this time of year is apply a foliar spray of iron chelate (pronounced “key-late”) to the leaves of your plant. It is available online and probably at a local big box gardening or hardware store for less than $15. It may take repeated applications of the spray to green up your shrub again.

But even a foliar spray is a temporary solution, effective for two or three months.

The next steps are to

  • Test the pH of the soil around the plant with chlorosis using an inexpensive pH testing kit which you can easily find online.  You may want to test other parts of your garden too.  (In fact, you may want to check the pH every year!)
  • Add chelated-iron fertilizer to the soil around the plant or tree IN SPRINGTIME (not Fall).  This is a longer term solution than the foliar leaf spray.
  • Dig in extra amounts of organic materials in the Fall and the Spring to balance the soil in your plant beds to a neutral 7 pH.  If you can get it to 6.5, all the better. Plants love 6.5 pH!  Keeping a high level of organic materials in and around the plants is a long term solution to chlorosis.
Rio Grande Fax Tex Ash autumn

BTW, if you have a Fan Tex Ash tree the leaves on it will naturally turn yellow in Fall. It is one of the very few trees for hot dry gardens that has lovely Fall color. (Of course, there are the aspen trees that grow in the mountains around the deserts and also become golden in Fall.)

CLIMATE CHANGE UPDATE

In an abrupt about-face the Australians tossed out their Prime Minister who announced last week that keeping fuel prices low was more important than meeting Paris Accord climate change limits. Among the first things the new PM stated was that climate change came first–particularly in light of the severe drought that is impacting ranchers in New South Wales, outside of Sydney.

Our 8 most popular newsletters

  1. Best and beautiful native shrubs for extreme heat
  2. Five fragrant plants for your garden
  3. Where to get free or cheap trees for your garden
  4. Six distinctively different landscapes to replace a lawn
  5. Cover up that naked wall
  6. Nine trees to combat climate change
  7. Four desert trees good for soil, 4 toxic ones
  8. Plants that bloom even in mid-summer scorching heat

Before and After: A surprising drought tolerant succulent garden

Just after I earned my Master Gardener certification I saw a low water usage succulent garden while visiting Long Beach, California.  It really stood out because most of the gardens in the area, less than 3 blocks from the edge of the Pacific Ocean, showed a strong tropical plant influence. Well, tropicals with roses.

Naples Island garden
Many gardens near the ocean in Long Beach used to be filled with tropical plants and roses. A small patch of grass as a “front lawn”was common. 

Back then there were no significant water restrictions and most homes had small lawns in front. Long Beach today has some of the most rigorous water restrictions in Southern California and it shows in the changed gardens.

A couple of weeks ago I was back in the same neighborhood and saw that drought-tolerant succulent/cactus garden again and took a photo thinking that I would show the change and maturation of the plants over the years. At home on my computer I looked closer and recognized that many plants in the garden now are almost entirely different from the ones back in 2003.

I realized that I had always thought of drought tolerant succulent gardens as being “eternal”–requiring almost zero upkeep and lasting forever. Not true–as this garden in its 2 incarnations shows:

Succulent garden BEFORE 2003:

Long Beach drought tolerant garden 2003

This garden in 2003 had the tropical giant bird-of-paradise (Strelitzia nicolai), on the left, but most of the other plants are drought tolerant succulents and cacti. The reason I never published this photo on Hot Gardens is because of the many New Zealand Flax (Phormium tenax) plants. These upright grass-like plants seem to simply die in hot, desert-like conditions which is too bad because they come in many sizes and great colors ranging from red to green to black and some nifty striped ones. Agave plants make up another important upright feature in this garden.

 SUCCULENT GARDEN AFTER 2018:
Low water usage garden Long Beach (

The giant bird-of-paradise plants are still in the garden, but now they have tall trunks leading up to the leaves at the top. Gone are the blue-green iceplants (Delosperma) that lined the sidewalk as are the New Zealand Flax plants. The Agaves have survived. And there are some tall tree-like plants in the parking strip that appear to be new. (Sorry I don’t know the names of them.)  It is, in a way, the same garden only different. And to be honest, I really like the 2003 version of this garden much better.

Our 8 most popular newsletters

  1. Best and beautiful native shrubs for extreme heat
  2. Five fragrant plants for your garden
  3. Where to get free or cheap trees for your garden
  4. Six distinctively different landscapes to replace a lawn
  5. Cover up that naked wall
  6. Nine trees to combat climate change
  7. Four desert trees good for soil, 4 toxic ones
  8. Plants that bloom even in mid-summer scorching heat

How much should you feed and water your garden in scorching summer heat?

For months now in 2018 the daily high air temperature has been above 90 degrees (F)  (32C) which means that plants in hot dry gardens in the Northern Hemisphere have gone into summer dormancy. Even drought-tolerant plants and natives just hunker down and try to survive until Fall when the air and earth cool down. (One of the few summer bloomers is the Crape Myrtle tree, shown above.)

As your garden’s best friend and caretaker, you should water the plants regularly, but do not fertilize the plants in your arid garden in an attempt to make them bloom or grow. They are thirsty at this time of year but not hungry now so deep irrigation is best. They do not want to grow. They do not want to produce seeds. And only a few bloom during summer dormancy phase.

Blooming color in summer

Crape myrtle white and pink
Crape Myrtle blooms in hot pink and white, both shown here. They also have paler shades of pink and even one with lavender blossoms. Best of all they love the heat!

My absolute favorite of the summer bloomers is the hot pink Crape myrtle (Lagerstroemia indica), a native of India and China that thrives all across the southern U.S. in both dry and damp climates.  By nature the Crape Myrtle prefers acidic soil, not the alkaline soils of the American West.  In the South where the soil is acidic and it rains in summer, the Crape myrtle grows to 20+ feet tall. In the very dry hot Southwest, the trees bloom beautifully but rarely reach that height.

If you are planning to plant a Crape Myrtle tree this fall after the weather and earth cool off, be sure to add a lot of organic materials to the soil around it and water the root ball thoroughly–soak it through–before it goes into the ground to encourage good root growth.  It’s a good idea to mulch around the tree every year so it remains happy and blooming every midsummer.

Climate Change Update

During this last month in the summer of 2018, people in Spain, Japan, and countries around the world experienced record-breaking temperatures of 117 degrees (F) (47 Celsius) and higher. Off the coast of La Jolla, California, the usually cool Pacific Ocean temperature was 78 degrees which is 10 degrees above normal. At the southern end of Florida, the water temperature reached 98F (36 C) Some fish, of course, can swim away from uncomfortable temperatures, but underwater plants and slow moving and non-moving animals are stuck and may die out.

Our 8 most popular newsletters

  1. Best and beautiful native shrubs for extreme heat
  2. Five fragrant plants for your garden
  3. Where to get free or cheap trees for your garden
  4. Six distinctively different landscapes to replace a lawn
  5. Cover up that naked wall
  6. Nine trees to combat climate change
  7. Four desert trees good for soil, 4 toxic ones
  8. Plants that bloom even in mid-summer scorching heat