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Wednesday, July 19, 2017

Challenges of Growing Tropical Plants in the Desert

MoCa Family Farm Is our farm in the Philippines. It is certified for agritourism and we are certified to teach many classes in tropical horticulture and farming through RLearniong Center. I would invite all of our friends to visit our Facebook page and become our Friends! We grow many different tropical fruits, vegetables, herbs and spices on our farm.
Q. What are the main challenges in growing tropical fruits in the desert?  Fruits like mangos, lychee, longan, jackfruit. It seems like Las Vegas has all the same conditions as Southeast Asia, except the humidity, but my understanding is that humidity is good for preventing disease. Are the 
colder temperatures in winter the only impediment to growing these fruits?

A.  Having a small-scale family farm in the Philippines and growing a wide variety of different fruits, herbs, spices and vegetables I can tell you the challenges can be many trying to grow these in the desert. There are some things we can grow quite easily while there are others that pose a lot of challenges. But I encourage people to try.

Many of our annual vegetables in the desert are perennial in the tropics. Take for instance tomato, peppers and the like.

Pruning guyabana (soursop) at MoCa Family Farm RLearning Center. We emphasize keeping our fruit trees small so they are easier to harvest.
But I think you are talking mostly about tropical plants such as banana, mango, papaya, perhaps tea, coffee. Each tropical plant presents its own set of problems. But as I tell many of my students, when you grow plants, the further these plants are from originating in the desert or desert adapted, the more time, energy and money it will take growing them.

Avocados at MoCa Family Farm
Here is a partial list of things to consider.

Temperature. Many tropical plants can handle desert heat but they cannot handle cold in any way, shape or form. Damage to tropical plants can start when temperatures drop below 50° F. Some tropical plants experience chilling injury at refrigeration temperatures. Think of putting a banana or tomato in the fridge. And of course freezing damage. When temperatures drop below freezing, most tropical plants cannot handle it. If you're growing a tropical plant that experiences these types of damage and of course you have to protect them from it. This might mean a greenhouse, hoophouse are wrapping these plants for thermal protection.

Immature rambutan growing in the Philippines
Light intensity. Sunlight is more intense in the desert and there is more of it than in most tropical climates. Planting tropical plants on the east or north side of a structure may be enough to protect them. Planting and filtered light such as from an open tree canopy or shade cloth may be enough.

Sunburn on Apple fruit growing in the Mojave Desert
Humidity. Some tropical plants and even temperate plants grow best with some humidity. In the Mojave Desert it is common to experience relative humidity at 30% or below for many days of the year. This can pose problems for some tropical and even temperate plants in flowering and fruit set. We experience fewer plant diseases in the desert because of low humidity.

Very poor fruit set on Bing cherry growing in the Mojave Desert with 12 other varieties of sweet cherry. I speculated it was because of low humidity and poor fruit set. Flowering was fantastic.
Soils. Surprisingly, tropical soils can have very low organic content and still be dark to black. Desert soils where rainfall is under 10 inches per year have unacceptable organic content even for cactus! Our soils organic content is far below 1%. The soil chemistry is usually unacceptable for many tropical plants with too much alkalinity and salts. Desert soils need organic content of 2 to 3% for lawns, palm trees, many of our trees and shrubs. 5% organics would be nice to have for fruit trees and 10% for growing vegetables. Even in the tropics, the addition of compost to the soil to grow vegetables is a very good idea if the soil has never been farmed.

Typical Mohave Desert soil in the Las Vegas Valley. Extremely low organic content.
Daylength. The amount of darkness a plant receives can act as a "trigger" for flowering in some plants. In the tropics daylength is not such a big deal since there is not much variation during the year. Instead, the alternation of wet and dry seasons can trigger flowering in some tropical plants.

I hope you can see that growing tropical plants in a hot/cold desert climate can be very tricky. How that plant is managed in our temperate, desert climate depends on which plant you want to grow. But in the very least you have to address soil barriers with compost and surface mulch, avoid planting in South or West facing exposures, keep them from freezing or possibly chilling injury and be aware of problems that might be associated with humidity. This is the bare minimum that you must think about if you plan on growing tropical plants in the desert.


  1. Is there any reference where someone can look up how much light, light intensity, humidity, soil, and growing conditions a certain plant needs?

    1. No, there isn't. It would be very helpful to people like myself if there were references about where and what type of climate plants were collected from. The best reference available that comes the closest is Hortus the Third https://www.amazon.com/Hortus-Third-Concise-Dictionary-Cultivated/dp/0025054708 and it is lacking ALOT.An example is Carolina Cherry Laurel. It is native to the southeastern United States but sold here in the desert Southwest. Then people buy them for desert landscapes and surround them with rock mulch (most of the nursery people wouldnt know so dont even go there). Then I get questions sent to me about why the leaves are scorching, yellowing and the tops are dying. Helloooo? That plant will grow here but not without a great deal of effort and putting it in the right microclimate. The same is true of citrus. We don't know the extremes that plants can endure until we try them. Then that information is passed on through experience. I don't want to get started but then we have all sorts of bad information floating around the Internet to compound the problem. There is good information out there to but the vast majority of information available is bad.