And you thought you knew that all trees were either deciduous or evergreen, didn’t you! Ha! Well it turns out that there is a bit more to it than that - at least as far as the “ever” in evergreen is concerned.

Anybody who grows tropical plants already knows that evergreen plants do shed their leaves from time to time - or all the time - and that it varies from species to species. Believe it or not, there is a branch of horticulture that studies the phenomonon of leaf change - Phenology.

Leaf-changing among evergreens in the humid tropics was the topic for the presentation by Dr. Francis Ng at the annual award ceremony at the Kampong. He is currently working in Malaysia but has an extensive resume including work outside the tropics in Europe.

His presentation focused on his efforts to see if he could find out what triggers leaf change in plants in the equatorial tropics. Why do they shed their leaves and flower at periodic intervals and, more particularly, what makes all flowering species do this en mass. This would seem obvious in temperate and sub-tropical areas where the climate changes from hot to cold or dry to wet periodically throughout the year. But even those of us in semi-tropical like South Florida, with obvious seasonal changes in day length and light intensity, often question what triggers some fairly extreme variations in timing and intensity of bloom as well. We may chalk it up to too much rain or dry conditions one year but no explanation ever quite seems to be perfectly predictable.

Even more curious is that there is often distinct synchronicity of bloom and leafing in the humid tropical areas along the equator where there is fairly uniform rainfall (wet or wetter) and little temperature variation throughout the year. So Dr. Ng’s study is searching for the cues that trigger trees in the humid tropics to shed their leaves and initiate flowers in flushes twice a year. Why are some flushes much heavier than others? Beyond the obvious flushes, plants in the humid tropics also produce smaller numbers of flowers and fruits continuously throughout the year. His hypothesis centers around changes in light intensity associated with more light at the semi-annual equinoxes and lower light when there is greater cloud cover during the monsoon periods.

Evergreen plants in Malaysia have two flowering peaks annually - the bigger flush in March/April and a second lesser peak in October/November. ALL plants flower synchronously during these peaks. Flowering is always associated with new leaves, but leaf change also occurs at times not associated with flowering. The intensity of the flush can be quite variable from year to year with occasional spectacular flushes once or twice in a decade. Botanists working in South America have referred to similar flushes in deciduous  wet/dry forests as “big-bang” flowering, saying it is a sight to behold.

Leaves become damaged, thin and fragile over a period of time and have to be replenished with fresh leaves in order to continue producing the chlorophyll that sustains life. Dr. Ng’s studies have shown that the more accumulated light the shorter the lifespan of a leaf.
It may be revealing to gardeners to know that there are several ways that evergreen plants change or shed their leaves.

Continuous exchange leafing describes plants whose leaves are shed and replenished continuously. Few trees in the humid tropics are truly deciduous. Some trees will drop all their leaves at once but begin to releaf almost immediately. This may happen several times a year. Others may shed their old leaves periodically as the new leaves are coming out and never be completely bare. Still others shed their leaves continuously throughout the year.

Leaf changing is associated with the intensity and amount of light the leaf receives. The more light a leaf receives the shorter its life span. Light intensity relates to its position in the canopy of a tree or in the understory. Continuous leaf exchange occurs in 90% of canopy species as well as plants like palms, papaya, Muntingia. I think Cecropia would be another example most of us know.

Flush accumulation type leafing species tend to produce new leaves in flushes which are clustered near the tips of the branches while the older leaves fall further down the branch. This is the typical habit of 90% of the species in the understory. Flushes occur more frequently in juvenile plants - up to 5 or 6 times a year and decreases as a plant ages.

Understanding these different types of evergreen leaf exchange is useful to horticulturists for understanding the characteristics of different species. How many times have we seen a young tree shed all its leaves several times in a season and worry that the leaves are yellowing or falling due to overwatering, cold, disease or dryness when they are actually just turning over leaves normally for their particular species.

[Dr. Ng's personal profile and assorted topics on horticulture can be found in his blog at http://tropicalhorticulture.blogspot.com/]

]]> http://www.tropicsphere.com/main/index.php/component/option,com_wordpress/Itemid,105/feed,rss2/p,38 http://www.tropicsphere.com/main/index.php/component/option,com_wordpress/Itemid,105/p,27 http://www.tropicsphere.com/main/index.php/component/option,com_wordpress/Itemid,105/p,27#comments Wed, 04 Feb 2009 19:08:05 +0000 spectre http://www.tropicsphere.com/main/index.php/component/option,com_wordpress/Itemid,105/p,27

Chlorotic leaf from an Improved Meyers citrus tree

Conventional wisdom says that California is a gardening paradise. According to the zone maps, one can grow whatever plant they desire within our state’s boundaries (yes, even a coconut if you happen to live on the Pacific Coast Highway in Newport Beach). As I write this on February 4, the high will be 75°F (23.8°C) on the southern California coast with inland locations reaching the low 80s (upper 20s C). If you live in central or southern Florida, Hawai’i, or in the Southern Hemisphere where it’s summer now, this is not a big deal. But for the majority of North Americans and Europeans, the today’s weather forecast is usually envied. Being the “glass half-full” kind of guy that I am, there is a flipside to our warmer than normal kind of winter if you are a gardener—especially if you love tropicals. This is the time of year we deal with “yellowing”.

Now I’m not talking about the lethal kind that afflicts palm trees in other parts of the world. The yellow I’m referring to is the sickly, dull, chartreuse that plants exhibit in California this time of year. Winter is usually tough on warm-climate plants in California unless, of course, the flora is native to a similar dry summer/warm winter (Mediterranean) or desert area. Even then, many get a pale 1970’s-like refrigerator avocado color in the leaves even though the plants are not avocados.

The causes for this are many and some are obvious. First, (of course) is that it’s just plain colder that these plants would like it. While we may be frost-free in many parts of the SoCal coast, we get colder nights and days and for a longer duration than other subtropical climates. Plants simply say, “it’s too freaking cold, I’m not going to die but I’ll pack it in until the nights warm up.” In other words, plants cells go dormant and leaves go dull. My favorite line is that your refrigerator is technically a USDA Zone 10, but you couldn’t grow anything in it.

Yellowing kentia palm (Howea Forsteriana) frond. Note the UFO in the upper left corner.

To add insult to injury, the prolonged “cool” exacerbates other challenges that SoCal gardeners face. There’s the salt air near the coast which definitely has an effect akin to sandpapering your skin and pouring alcohol on it. As if salt in the air wasn’t bad enough, we get more than our share of salt in our irrigation water, much of it imported from the Colorado River. Now you don’t need to be an geographer to know that the Colorado is the reason the Grand Canyon exists—and is still being sculpted to this day. Those really cool looking rainbow-hued layers have to go somewhere and, you guessed it, it’s in the soil your palm trees are planted in.

You’d think that all these minerals in our water would at least deposit some iron in the soil which is required for plants to photosynthesize and, in turn, stay green. Well, maybe it does but I wouldn’t know by the yellow plants I have. Another cause for yellowing leaves is what plant geeks call chlorosis which is a fancy word meaning anemia for plants. Do you remember the last shampoo and conditioner commercial you saw on TV and how they threw the term “pH” like it means something for you hair? Well, it also means something for your soil too. If the soil pH is too high (i.e., basic), you can have a ton of steel wool, nails, and Geritol composted into the dirt but the plant roots will not uptake the iron. This, of course, results in more leaf yellowing.

But wait, there’s more…. Stay tuned.

By definition, a native species is part of a specific habitat, sometimes very local and sometimes widely distributed. Each species in a habitat exists in balance and is supported by all the other species and conditions in its particular niche. The word is mistakenly used to mean plants of a general area. Here’s an example taken to the extreme just to illustrate how absurd that is: By this logic you could say a polar bear is native to the northern hemisphere. Or you could say it is native to the United States. Obviously you know polar bears are not native to Florida or even the southern states but both are within North America and the United States. Polar bears are actually native to areas of the sub-arctic region in a habitat that includes specific climactic and ocean conditions, temperature, tundra plants and the seals and other animals it preys upon.

In South Florida many people are given to equally absurd geographical slight of hand when they refer to species from specific regions within Florida as “Florida natives”. This suggests that a ghost orchid, for instance is native to all of Florida when it grows exclusively in remote areas of the Great Cypress Swamp SW Florida. It is very difficult to grow outside that habitat. That is important because it is almost impossible to grow it successfully elsewhere and removing it only leads to extinction. Obviously the ghost orchid is not a “Florida native”—a state that covers temperate to subtropical zones, swamps, hardwood forests, grasslands and several types of coastal forest and dunes, each with its own flora and fauna.

The point is that even so-called “native” species may or may not be appropriate for a particular garden depending on suitable conditions that resemble a species’ true habitat. Indeed most of the attributes of so-called “native” plants, such as water conservation, food and wildlife habitat can be found among a wide range of suitable non-native species from other parts of the world with similar climate. And some foreign species may even have advantages over local species such as being more drought tolerant or less weedy because they are sterile in cultivation or because they lack pollinators. Certain non-local species may be resistant to local diseases and insect pests than true natives.

But politics, governmental and environmental, has largely drained any meaning from the definition of the word. And at the same time people who lack a reasoned understanding of the word often treat cultivated species of plants as second class citizens no matter how benign.

An example: by misrepresentation of the term “native”, Miami-Dade County requires the planting of 60% “native species” in all new development. Believe it or not, some of the plants on the so-called “native” list for Miami-Dade County are native only to parts of different counties such as the Keys or extreme southern coast of the mainland (mahogany trees, lysilomas). It certainly is not important to the powers-that-be which species are actually native to the particular habitats where our homes now stand, former seasonal wetlands, rock pinelands, hammocks or coastal mangrove, woodlands or grasslands, as long as what we plant has been growing in South Florida for a long time. In addition, some actual natives of local habitat may be totally inappropriate for suburban life such as the scrub pines that used to cover Pinecrest. They are intolerant of lawn irrigation, construction and septic systems and may topple in hurricanes or act as lightening rods.

Consider the idea of reintroducing plants that were former natives into an area where the native oolite lime stone is now crushed and covered by truckloads of non-native fill from who knows where. Consider that the live oak (Quercus virginiana) is on the list of native plants that are allowed in Pinecrest.  This oak was never native to rock pinelands. Fires used to scour the pinelands of hardwood trees. Fire no longer is welcome in former pineland regions. Oaks now are self seeding pests in our area and crowd out many true natives that formerly grew here given their rampant suckering habit when the crown is damaged or pruned. So what that it is native to coastal hammocks and northern Florida.

In stark contrast to proprietary laws governing the use of “natives” in new landscaping there is mediocre enforcement to control invasive species sold by nurseries and a failure to ensure invasives are removed from new building sites. These species can destroy what little native habitat we have left and cost taxpayers millions to keep them in check. These species will inevitably alter the Florida landscape.  Any self-propagating species outside its habitat has the potential for becoming invasive and that includes some so-called “Florida natives”.

Because of political pressure and government failure to act quickly they have been totally ineffective in removing seriously destructive pest animal species as well. Introduced animals also lead to the destruction of natural habitat and native species of birds and other animals. While we have laws restricting our use of harmless introduced plants, feral cats are allowed to wander freely and decimate the songbird population. Some areas of Florida are overrun with iguanas, monitor lizards and pythons. In effect “native police” are often agressively barking up the wrong trees while serious conservationists have their hands tied.

Wouldn’t it be more effective and economical to concentrate our efforts on preserving wild areas that have not already been decimated by habitation? Of course but who expects reason from county government.

And what about the signs that many species adapt? Are our pols aware that bird species like the swallow-tailed kite prefer Australian pines over our native pines for nesting places? Several dozen of these magnificent black and white aerialists are no longer nesting in Pinecrest since many of the pines trees  were removed because they are invasive in beach areas such as Crandon Park. Australian pines may break in storms but they regrow quickly restoring habitat while native pines are destroyed by storms when topped and are very slow and resistant to reintroduction.  A few isolated trees do not propagate themselves readily when restricted to private property inland.

Officials must love an excuse to levy fines or they have been misled to think that there is some magic in a plant because it is described as “native”. Our landscaping codes are a farce because they are based on inaccurate assumptions and definitions. We have misplaced our priorities and continue to divert our attention to relatively minor issues instead of tackling the tough issues of urban sprawl, efficient mass transportation and preserving still wild habitat before it is too late.

Home owners should have free choice of non-invasive species. Many introduced species will provide habitat, nectar and food for wildlife. At the same time they should know that many so-called natives can and often do become as seriously invasive as any “exotic” plant. Laws requiring the planting of so-called “native species” in suburbia at the exclusion of well adapted introduced species does not prevent the extinction of a single endangered species.

It’s high time to get some perspective. It’s a fact that some introduced species can be extremely invasive and usurp native habitats. Humans are the ultimate exotic species. We depend on agricultural and animal species from around the globe for our survival.

© Kirsten Llamas

But now it looks like real life is breaking down the doors of my sanctuary and the troubles of the financial markets will impact horticulture and gardening in ways never seen in most of our lifetimes.
The economy was already stinking with housing values in the US (and now other parts of the world) tanking, the subprime mess, and the escalating cost of commodities. Though oil and other commodities have eased back from their July 2008 highs (due to speculator’s fears that demand will slacken), the latest investment firm fiasco with The US Federal Reserve Bank and Treasury playing “whack a mole” by putting out one major Wall Street fire after another has caused a financial crisis and panic not seem since the Great Depression of 1929. With the original money market fund “breaking the buck” last week (paying 97 cents on the dollar) which is unheard of, AIG essentially being taken over by the US Federal Government, and continued news of bank failures braking every day, this “[sic] sound fundamental economy” of ours as viewed by John McCain thirty-six hours before he recanted is starting to impact everyday life.

As people consider going back to stashing their cash under their mattresses waiting for the next economic boom to be dropped, people in the nursery industry are feeling the pressure as discretionary income is diverted from plants, landscaping, and horticulture to more mundane things like making sure the house paid for, there’s food on the table, and gas to put in the car to get you to that job that suddenly doesn’t seem as rock-solid secure as it did just two weeks ago.

I’ve spoken to a few folks in the trade in southern California and people who’ve been in the game since the eighties say this is the worse they’ve ever seen it. Some are wondering if they will make it to the end of the year. Add to that the water restrictions, widespread drought, and skyrocketing prices of commodities like fertilizer and 2008 is a year many growers can’t wait to end.

Up until the latest meltdown, people (at least in the United States) were already dialing back the budget for travel, opting instead for a “staycation” which means taking a rest within a few hours drive of your house (or more often, in your house). To make the staycation more pleasant, people were still forking over coin for amenities to add to the “escapist” feel—things like outdoor kitchens, patio tables, and accessories. Of course, plants were added to the mix because as all of you warm climate gardeners know, nothing says paradise like a palm frond rustling in the wind. Earlier this year, Business Week reported the big box stores ramping up the inventory and quality of the aforementioned goods and it definitely showed at my local big-box.

Now, this was bad news and bad news for our favorite growers, the independents. Yes, people did spend some money on home improvement, but they did it on the cheap which favors the Home Depots, Lowe’s, and Carrefours of the world. Instead of buying slightly-rarer, yet more costly specialty plants, the average buyer went with the big boxes. One local sold the exact same (new for 2008) bat-faced cuphea this past May for $4 more per plant that HD (differential due to volume purchases)—how can they compete with that? With the masses going with the cheap stuff, that leaves the enthusiasts like us to support them but we’ve all been screwed by the same greedy bastards on Wall Street. That means that we’re just as concerned, just as impacted, and just as tight-fisted with our money as the general public.

The big boxes will weather this financial hurricane but the same can not be said for the mom-and-pop nurseries out there that do it for the love of the plants. Unfortunately, many of them will not be around this time next year and we will be worse off for it. We can help by continiung to support these places when we can and spread the word that the plant palette is not just composed of carrotwoods, impatiens, and queen palms. In my talks, I am often asked what nursery sells a particular plant that my PowerPoint interested them in and 9 times out of 10 my answer isn’t Home Depot. I will try to do my part to use the website to make gardeners aware that these plants and vendors exist—I will use the forums, blogs, outpost and any tool at my disposal to make sure that the good nurseries continue to get some play. Unfortunately, we’re a bit small to have any real impact, but as we grow, my goal is to make this a clearinghouse for this kind of information. Obviously, I can’t do it alone—you all need to help out in anyway you can to keep the independents afloat because if you think that holy grail plant is tough to get now, just wait until 2010.

In the mean time, buckle your seat belts and make sure your seats and table trays are in their upright and locked position because our favorite haunts (as well as us) are in for some nasty turbulence ahead thanks to the free-market fanatics on Wall Street who thought they knew more about risk management and lending than the risk managers and lenders themselves.

©2008, Tropicsphere

There are a ton of new royal palms going on Ocean Avenue—and I’m not talking about the one in Miami Beach.

The DW and I spent some time up in the Los Angeles area taking in the sites after a night of primo salsa dancing, revelry, and good-ol’ wholesome debauchery. When we were deciding what to do the day after, my wife mentioned that she wanted to return to San Diego via the coastal route so she could see many of the beaches that, well she’d never seen before. Southern California has a lot to do and unless you’ve lived a hermetically-sealed time capsule for the last hundred years, you are bound to see a beach that you’ve seen on television, movies, and now videocasts.

I told her that this isn’t like Highway 1 near Big Sur (well technically, most of it is Highway 1 but that’s besides the point). The drive and scenery are what the Cabrillo Highway (SR-1) are about in central California. The Pacific Coast Highway is more like, “look that’s where Mitch Buchanan saved Pamela Anderson” or “that’s where Jack Tripper falls off the bike in the intro to Three’s Company” or “that’s where John Cusack recovers from a surf wipeout in 1408.” When I said we wouldn’t get home until 2019, she agreed just to head west and see where it took us.

So after we checked out of the hotel and made the customary pilgrimage to Leon’s excellent nursery XOTX Tropico, we headed west on Sunset Boulevard on our journey to the sea. We drove by the Sunset Strip, Beverly Hills (wasn’t that the street where Jed, Granny, Elly-May, and Jethro drove), Bel Air, and UCLA. Next came the 405 and after that Bundy Avenue. The DW said, “that sounds familiar.” I replied that Bundy was the street where Nicole Simpson and Ron Goldman were “allegedly” killed…errrrrr…not killed by O.J. Simpson. But to my delight, she said that wasn’t it—it was Ted Bundy the serial killer she was thinking of—and the Bundys on Married With Children. That made me feel great because I hate the celebrity-obsessed culture we live in and I couldn’t care less about O.J.

So a few miles down, we passed Rockingham and I noticed they removed the median barriers. That meant that O.J.’s mansion and the neighborhood returned to normal. Uhhhhhh—I think I saw that from Mystery on PBS, that’s it. We then entered Pacific Palisades and finally intersected with the Pacfic Coast Highway (or PCH as it’s known around here). We headed south towards Santa Monica and my wife saw the Santa Monica Pier. I knew what was next—”let’s stop there.” So I came the long way around before the PCH turns into the Santa Monica Freeway (I-10) and exited onto Ocean Avenue and drove north along Palisades Park.

Palisades Park is famous, not only because of the pier that anchors the southern end of it. It doubled for “Santa Rosarita” in It’s a Mad, Mad, Mad, Mad World—the steep street that they chase each other on is the California Incline, which goes from the bluffs back down to PCH. The “W” which marked the buried treasure was there. The pier was featured in Ruthless People at the end when the LAPD chase Judge Reinhold’s character to the end of pier and Danny DeVito gets kicked in ocean by Bette Midler. US Route 66 used to end there. It’s been filmed so many times, you’re bound to see something makes you go experience deja vu.

But since this is a garden and travel blog, let’s get to the plant part. Of all the things that surprised me there is the recent planting of hundreds of royal palms or Roystonea regia to be precise. Now, on Ocean Avenue in Miami Beach, this wouldn’t make grandpa’s 35mm print he sent to you because he thinks a megabyte is the new burger at Wendy’s. But Ocean Avenue in Santa Monica? Amongst the aloes, agaves, bougainvillea? Next to Mexican fan Canary Island dates, and king palms? Huh? But they were there, recently planted, double staked, and frizzy-tipped from shock. WOW! Now most tourists there that day couldn’t give a rat’s asssssssssss about these scraggly looking specimens that look better suited to be removed so there are more places to lie out in the sun. But they were there—about two miles (3 km) of them—strategically planted in what will one day be cool looking rows. Most were planted in the bermuda grass, but some made it in the beds of low-water bedding plants like Carissa, manzanita, and Ceanothus. I’m not sure how those will do, especially when I recently heard that LA’s Department of Water and Power will move to permanent rationing soon.

I know one advantage to being a gardener is the irresistible urge to spoil TV shows and movies for everyone else by pointing out the flora mismatch with the supposed locale. A famous one, even among non-plant enthusiasts, are the palm trees you see in Reno-911. Now, Reno is in Nevada’s Great Basin at the eastern base of the Sierras about 4,500′ (1,500 m) in altitude. They get hard freezes, snow, and lows that can be frosty almost any day of the year. You can watch USA’s Psych and know it’s not in Santa Barbara because there never is a palm tree (it’s filmed in Vancouver, British Columbia). The same is true with shows filmed in Florida and California. If I see royals in a show based in Los Angeles”, I know it’s being filmed in Florida. If I see a CSI-Miami with excessive Mexican fan palms and Canaries (especially with a hint of the Sierra Madre Mountains in the back), I know that was filmed in SoCal.

With these royals in Santa Monica, that destroys all of my fun. When they’re full-grown,  fat, white trunked palms, how will I know that what looks like Florida isn’t actually California? I don’t have to worry though because the lousy drivers will always give it away…. It’s a great place for them (outside of the cool marine air). Santa Monica is one of the few places in the continental USA never to have recorded a freezing temperature. That area is also one of the few parts of Cali to be Zone 11, and there are some great microclimates there that allow tropical plants to be grown that can’t survive a winter anywhere else in the state, including San Diego. This is a very interesting development and for a palm lover like myself, a great one.

Just like I thought—it’s almost 17:00 and it’s time to head home. My wife was too pooped to see Venice Beach, Palos Verdes, and (of course) the famous northernmost coconut palm in Newport Beach. She said, “just get on the 405 and go home.” Wimp.