Blight, Plague, Disaster, and other Maladies of Monoculture

Panama Disease
on Bananas

Some months ago I saw an interesting public-television program called "'The Botany of Desire", which was less salacious than the name suggested. It was based on a very popular book of why we have had affinities for some notable plants such as Tulips and potatoes. What caught my attention was the amount of detail given to the visually unremarkable modern potato, the vast majority of which is grown for the fast food market, primarily McDonalds' restaurant outlets. The problem is that just 1 variety is grown, the Burbank Russet variety, to the exclusion of virtually any other variety, since its long shape is perfect for making french fries that are long enough to stick up out of the serving container. Why would well-trained potato agronomists plant all of their farms with just one variety of a plant ? The answer is "money", since that plant type is what will sell or what is demanded. Why would such an agricultural method be noteworthy for a television program? The answer is "monoculture".

Potato Blight
the same disease that caused
Ireland's potato crop to fail

Growing vast acreage or countless thousands of a single variety of anything is a prescription for trouble. Many growers and cities and landscapers use large quantities of the same plant, whether it is  a coconut palm, Oak Tree, Elm, Ficus or Ash. If an insect or pathogen is introduced into that monoculture, the invader can undergo an unrestricted population explosion. Many areas of the world have seen whole provinces wiped out due to a disease. There are numerous examples, but some of the historically larger ones have been Panama Disease in Central America; Lethal Yellowing in palms in the New World, especially Florida; Potato Blight in the UK; Dutch Elm Disease in the eastern USA; Emerald Ash Borer in the eastern and northern USA; Hypoxylon Canker throughout the USA, and the list goes on and on. In Florida, we are at the forefront of introductions of new pests, and the range is broad, including fungi, bacteria,insects, reptiles, and of course, weed plants.

Dead Coconut palms in Jamaica,
due to Lethal yellowing
Sometimes the pests are part of a suite of problems, where a weed is introduced along with a pest, or an animal + pathogen combination is introduced, such as African Giant Land Snail containing the the parasite which induces human meningitis. Left unchecked in a monoculture, any pest or pathogen can wreak havoc and in some cases, throw a country into chaos, as in the Great Famine in Ireland in the late 1800s and early 1900s. Guatemala suffered terribly as its stalwart banana crop died in the early 20th century due to a highly contagious fungus ripping through massive plantations of the same kind of plant. Jamaica has seen its coconut plantations decimated by Lethal Yellowing. There have been grain and fruit crop failures which nearly bankrupted Asian countries. The numbers of dead plants and the amount of damage from introduced pests and diseases is hard to comprehend, certainly and provably in the billions of dollars. 

Dead Dutch Elms,
killed by Dutch Elm  Disease
The evidence is clear that over-planting a single variety of plant is just waiting for a problem to occur that will wipe out that crop . Yet in so many cases, municipalities and agriculture and homeowners repeat the problem. There needs to be much greater education at levels that diversity is the key to preventing such outbreaks, along with better landscape management practices. There are far better choices available to us now for disease-resistant plants than were available 30 or 40 years ago. We have a much better understanding in the landscape trade of the importance of looking into a plant's history to see if there are disease problems, but there are still too many instances of planting susceptible plants, and planting too many of them. 

The solution to monoculture is to plant a greater diversity of disease-resistant plants. An integrated solution calls for better education of nurserymen, landscape designers, and homeowners. The University Extension services of the US perform this function, but too few people pay attention to their please for education. These Extension Services are perennially on the budget chopping block . It is these researchers and information agents who can solve these problems for us at no charge to the residents, but they are underused and underpublished. As always, I make the plea to use information resources effectively to become educated. 

Craig Morell
Pinecrest Gardens                         



The Remarkable Tillandsias

T. stricta

Having grown bromeliads for more than 20 years, I am constantly amazed at how diverse the family is. One of the more durable groups is the genus Tillandsia, often called ( wrongly) "air plants". I have grown to appreciate their durability and colorful flowers, which often last a very long time. There are hundreds of species, from petite tufted species under an inch tall to 7 foot-diameter giants that weigh hundreds of pounds. The natural habitat for this genus is quite diverse, with climates ranging from cool, high-mountain aeries to the most brutal of desert climates, but all species are New World. I see so many instances of the smaller species glued to a seashell or piece of driftwood, sometimes with a magnet attached, and sold at retail stores as plants which need no care, thriving only on air. Let me clarify the culture of these remarkable plants. 

T. duratii

 Most of the species likely to be found in the retail trade are the so-called "hard leaf" varieties, which grow naturally on trees in large clusters, surviving on fog, rain, and organic matter from the plants above them. In most cases, they grow in very bright locations, often in all day sunlight. The brilliant flowers attract insects, hummingbirds and small nectar-feeding birds. In the case of the amazing T. duratii, the beautiful blue flowers also have a strong smell of grape juice !  

one of the giant, soft-leaf species
from highland Mexico

In most cases, these plants like to be mounted on pieces of rough wood, or in a slat basket to allow the roots to breathe. The plants will grow and bloom best if they are given very bright light, with  at least a few hours of direct sunlight per day. In the case of the silver-leaved species, 6-8 hours of sun per day is required for good growth. The plants take up most of their water and nutrients through the foliage, and have very limited root systems. This allows the plants to be glued to almost anything, since the roots are functioning only as anchors, not as means to take up water or fertilizer. Spraying the plants with water or dilute fertilizer is the best water to cultivate Tillandsia species. The main mistake people make with Tillandsia culture is they shade the plants too much. In so many cases, the plants grow in very bright light or direct sunshine in nature, not sitting on a kitchen counter. Once you discover how rewarding the plants can be when grown properly, there is a world of species available at very low cost, which propagate themselves readily, require very little care, and show off some of the most brilliant and complex flowers in the plant world.     

T. jalisco-monticola
with blooms that last for months

T. prodigiosa
from misty mountain forests

T. fasciculata
native to South Florida,
in bloom for 4-6 months

T. magnispica
with a 24 inch tall flower stem
 Our native T. fasciculata comes in many color forms, the most richly colored of which are ruby-red, shining like jewels in the gray-brown forests of winter-dormant Bald Cypress Trees. Given the diversity of the genus, I am still curious as to why people have so little knowledge of what is available. The supply of plants is extremely good, although I must admit that if all you have for the supplier of bromeliads is a garden center in Des Moines, Iowa, the garden staff may not have much demand for the larger species. There are numerous suppliers of species on-line, and the service from them tends to be quite good. I encourage people to experiment with these wonderful plants, but give them plenty of sunlight. You will be rewarded with long-lasting flowers of surreal beauty

Craig Morell
Pinecrest Gardens       


The Giant Leopard Orchid

G. speciosum

The genus Grammatophyllum is fairly small, with at most a dozen species, most of which are solid, sturdy plants of a few dozen pounds. A few of them, however, are giants which can weigh hundreds of pounds. The smaller species have pseudobulbs the size of avocados, bearing 3 foot leaves, with flower spikes up to 4 feet long showing off 70-100 spotted flowers 3 inches across or more. Large plants of this section of species can be 6 feet across. The larger species, such as G. speciosum and G. wallisii, have cylindrical, cane-like pseudobulbs up to 7 feet tall, with 6 foot leaves. The plants can have flower spikes 8 feet long, bearing hundreds of heavy-texture, spotted flowers. Individual plants can span 25 feet, sometimes more, and weigh up to 1000 pounds. 

G. speciosum at the Singapore Botanical Garden

G. scriptum

G. scriptum



G. martae,
a rich chocolate-colored species

G. Tiger Paw
primary hybrid of G. elegans and G. scriptum
 Growers often say that their plant is as big as a small car, leading me to quip that perhaps they own a VolksOrchid. In all instances, though, these are big plants, not for the heat or space-challenged grower. The plants are easy enough to grow with the same care as Vandas,with similar needs for heat and light. The major difference is that Grammatophyllums need far sturdier baskets in which to plant them ! Many growers have found that these species need a semi-terrestrial culture. Interestingly, some of the growers in the northern US have found that the giant Grammatophyllums grow well using the same potting medium as for Cymbidium, to which they are closely allied. With plenty of sunlight, heat, abundant watering and a nearly continuous supply of nutrients, the Leopard Orchids are both rewarding and impressive at the same time. They are, however, unforgiving of periods of long, cool weather, lack of light, or near-tropical temperatures. This plant group grows well if you have the conditions for it, but don't expect it to easily adapt to your greenhouse in Minnesota unless you wish to pay for a lot of heat and electricity. This is the right plant for the right location, and we are lucky to live in an area with the right conditions for it. 

Craig Morell
Pinecrest Gardens         


Oil Palms--A Case of Two Identities

An American Oil Palm

In our amenable climate in Miami, we can grow many thousands of different plants. Even when speaking about plants using their specific Latin binomial names, plants can be confusing and difficult to keep separate. The use of common names in plant naming is even more confusing, and can lead to some cases where plant choices can be badly mixed up. Such is the case with Oil Palms, which can have twice-confusing names. There are the tall, slender and regal American Oil Palms, and the shorter, broader, African Oil Palms. The American group grows rather slowly, whereas the African group can grow with surprising speed, becoming a weed in some climates. I say that these groups have twice-confusing names because there are members of the African Oil palm group which are native to the Americas, leading them to have a common name of American Oil Palm ! We then have a problem of 2 radically different genera, from largely disparate continents, with the same common name in the same plant family.

 I have been taken to task rather often about my interest in using the highly specific Latin plant names since many people feel this has a snob aspect to it. I disagree, replying to those critics with "how would you describe your car? The thing with 4 wheels and shiny paint ? " People can describe their property with amazing detail, but seem uninterested to describe their valued plants with similar detail. Let me add  some clarity to this conundrum of the Tale of Two Palms. 

young American Oil Palms
in a landscape setting

The American Oil Palms, comprised within the 4 genera of Attalea, Scheelea, Maximiliana, and Orbignya, are tall-growing feather palms, often growing to 50 feet or more in height. They can grow as much as 40 feet before they even form a trunk. All species in this group grow in the New World, most are from South America.

African Oil palm
Elaeis guineensis

The African Oil Palms, all of which are in the genus Elaeis, are Old World ( usually) and one species in the New World. They are fast growing, often more broad than tall, and are the primary commercial source of palm oil, with many thousands of acres / hectares in cultivation, especially in Asia. Both are good landscape plants, although the American Oil Palm species, in my opinion, are vastly superior as regal and imposing specimens especially well suited for boulevard and park plantings. The African Oil palms are easier to locate in many nurseries, since the palms set copious seed which sprouts easily. The palms will rapidly grow to 20 or 30 feet tall in a few years with moderate care, but require more pruning care and more fertilizer than an American Oil Palm.            

seedling African Oil Palms
As with so aspects of landscaping, there are many choices available no matter where you have a landscape. So many people use the same few plants they see in their neighborhoods, and even landscape architects have a rather limited palette of plants, perhaps favoring those choices which have worked well in the past. There are such good information resources available to both professional and home landscapers--why not use the information available ? The plant world has wonderful diversity; use it to your best effect !

Craig Morell
Pinecrest Gardens     


Is it Really Possible to Stop Plants from Growing ?  

A Good Example of Growth regulation in Annual Flowers
unregulated on the left, well regulated on the right

The answer is "not really". It is possible to slow down plant growth in the case of many ornamental plants, but to completely stop plant growth is almost impossible. We hear a lot about the term "growth regulators", without which many millions of commercial plants would grow too tall and too rank to be worth selling. Millions of annual plants, Poinsettias, Chrysanthemums , and even flowering hedges are routinely treated with growth regulators to "slow down" their growth to make the plants fuller and denser.

Many Hibiscus sold in retail markets are treated this way, and the results are amazing; the plants are full and compact, with a gorgeous deep malachite-green color, and lots of flowers on a small plant. If you look closely at the stems, however, you would notice that the leaves are almost stacked on top of each other, with a very short internode space between leaves. When the growth regulation chemical wears off, the plants will grow with their normal speed and size. This effect happens with all regulated plants, and the difference can be striking, especially in a bed of annual flowers when the chemical wears off, where the plants may grow at different speeds throughout the bed, yielding some almost comical results of dwarfs-and-giants next to each other.     

A Growth-Regulated Hibiscus,
Ready for Retail Sale
 Plant growth regulators, abbreviated as PGRs, have distinct and predictable properties. The consistent application of these products to the plant surfaces, as well as the timing of the application, are key to producing a well-regulated plant crop. The products are generally not used in landscape scenarios, and rarely available for consumer usage. The products are expensive in many instances, and if incorrectly used could result in stunted and disfigured plants. Several commercial growers, as well as an increasing number of landscapers have found that using too much PGR or too often can lead to disastrous results in some very expensive plantings. as with any chemical, the right product for the right purpose applied at the right rate will have the desired effects.

One of the Most Popular PGR Products

There are PGRs for turf grass culture, especially useful in the golf industry, where height control on golf turf is important. Some of the PGRs can cost $ 500 per gallon or more. In the landscape industry, some companies are seeing the benefits of using PGRs to slow down the unruly growth of some hedges, especially Hibiscus and Ixora. In the right scenario, such products save a lot of trimming costs. For homeowners, the main thing to remember is that some flowering plants purchased at landscape nurseries and retail outlets look "better than reality". This is what I call the Cosmopolitan effect: the person you see on the cover of the magazine doesn't look like that in reality. The plant you purchased will never look as good as the day you purchased it, but will grow into a healthy "normal" plant once the chemistry wears off. This is a good case for "Buyer Beware", but in these instances, there are no hazards or hidden problems with PGR plants, just expect that like kids and baby animals, they'll grow up.