Sahara in South Florida?

June did not waste any time coming and going, and we're already pushing mid July.

Though it's been raining about a mile inland, we've been unusually dry here on the coast. The westerly seabreeze from the Gulf is keeping the summer storms from making it to us. According to our rain gauge, we got only 2.39 inches of rain in June, and most of that fell in one enormous thunderstorm. The rest of the rain fell in increments of a few hundredths of an inch, not enough to wet more than the very top layer of sand.

 So far in July, we've had 1.01," with little chancce of more before the end of next week. ( I have to be careful about what I wish for. I was lamenting the drought in May, and we ended up with over 15 inches here at the house). I save as much rainwater as I can, but I have containers for only 40-50 gallons, and I've used it all. I irrigate as little as possible, almost on a triage basis, but if this dry spell lingers too much longer I definitely will have to drag the hose around.

Dune Sunflower, Helianthus debilis, a semi-vining, scrambling beach native.  It takes  major drought to slow it down.

It's hot. Hot and humid, with heat indices in the 100's for most days. The whiteflies are going to town, and it's time to dispose of  expiring tomato and pepper plants. Native plants are far from immune, one reason I pulled out bushels of spent Gaillardias about a month ago. In Florida Weather, Morton D. Winsberg writes, "... air over Florida in summer becomes so humid that conditions are similar to those during rainy season in the Amazon or Congo basins." (p.94). By afternoon in summer our skies typically are hazy, even milky due to the humidity.


The weather may have been keeping me indoors for much of the day, but life in the garden continues at a frantic pace. The Lignum vitae, Guajacum sanctum, completed a glorious flush of blooms the last week of June. The blooming period is short - only about a week - but the intensely blue-to-violet flower petals are so gorgeous that I can't mourn the briefness of their stay. Besides, there will be more flushes as the year progresses.

Lignum vitae, Guajacum sanctum

This very slow-growing tree has shiny evergreen compound leaves and deeply textured grayish bark. It will grow tall and spindly in deep shade, but given more sun, it often develops a somewhat spreading habit. The trunk of the one in our yard is virtually prostrate. It had to grow out instead of up to get the light it craved, and two hurricanes enhanced the lean.  The plant definitely adds to the garden even out of bloom. Birds love to perch in it. The ornamental seed pods remind me of small golden turbans. They open to expose shiny black seeds covered with a fire-engine red flesh which mockingbirds and cardinals relish.

Open Seed Pods and Shiny Red Flesh Covering the Seeds

Since this tree has such a slow growth rate, it's not surprising that the wood is extremely tough. It is so heavy it won't float. The high resin content - about 30% - means that items made from the wood are self-lubricating, and it has been used for centuries, especially in shipping, for bearings and pulleys, and in food-handling machinery to avoid contamination. Gil Nelson writes, "Hinges made from lignum vitae served the locks of the Erie Canal for over 100 years." (The Shrubs and Woody Vines of Florida, p. 371).

 The resin gives it great tensile strength as well. Belaying pins, cricket balls, croquet mallets, British police truncheons, and mortars and pestles are some of the many other items made from this wood. Lignum vitae wood was used for the "aft main strut-bearings for the USS Nautilus," the first nuclear sub in the world. An item of trivia : images of the flowers, which are the state flowers of both Jamaica and the Bahamas, were embroidered in Meghan Markle's wedding veil. (Most of this information is from the Wikipedia article on Lignum vitae).

The discovery of the wood's qualities coupled with the fact that its sap could be used to treat symtoms of syphilis, meant that from the 1500's on, vast quantities were cut and shipped to Europe. This native of tropical America, from roughly northern South America to the Florida Keys, is now endangered. Fortunately it can be grown from seed, and grows well in cultivation. If you ever get the chance to visit Lignum Vitae Key State Botanical Park, don't miss it! Lignum vitae key has one of the very few, perhaps the only, virgin tropical hardwood hammock left in Florida.

Now, back to the Sahara. In spring, summer and early fall, vast clouds of dust from the Sahara desert collect in masses 1-2 miles deep, and 5,000 - 20,000 miles high in the atmosphere. These clouds of dust can be as large as the continental US. The Saharan Air Layer, as it is called consists of hot, very dry dusty air containing much mineral dust, and can be associated with strong winds. It tends to weaken or depress tropical storms, especially tropical cyclones moving across the Atlantic. (article by Jason Dunion. I can't get a direct link to the article to work, but you can find it on the NOAA website. In the search box type "Saharan Air Layer," and it should take you to the article). Because it blocks the sun's rays, it also diminishes local convective thunderstorms, which along with seabreeze collisions are a major source of Florida's summer rain. While the SAL is in place, we can pretty much forget about rain. I don't think the SAL extends much farther north than South Florida in the U.S., but I haven't been able to confirm that yet.

For a fascinating overview of the contents of Saharan dust, and the effects it has on the earth, including fertilizing the Amazon and sequestering carbon in the ocean, read Jason Adetunji's article, "What Dust from the Sahara Does to You and the Planet." (I can't get a link to work for this article either, but it appeared appeared in theconversation.com. You can find the article by entering the title in the search box).


The reddish soil in an agricultural area in Miami-Dade County known as the "Redlands" is possibly the result of tons of deposited Saharan dust, which contains iron particles.

Scarlet Sage and Dune Sunflower