How Does Fruit Ripen?

I've never really known what happens when a fruit ripens, except that ethylene gas is released and somehow triggers the process. And that bananas give off a lot of ethylene as they ripen, leading to the well-known technique of stimulating ripening by enclosing fruit together with some bananas in a paper bag.

That's not a lot to know about it, so I went to the Google machine (actually, I use Ecosia, a very capable search engine that sends 80% of its surplus income to good causes, primarily tree planting). Up popped a clear and non-technical explanation of the ripening process at a website maintained by Professor Ross Koenig of Eastern Connecticut State University.

It's a complicated world out there, of course, and there are many ways that fruits carry out their miraculous transformations. But typically, as explained by Dr. Koenig, an unripe fruit contains acid (hence the sour taste), starch, pectin (basically the glue that holds the cells together, making the fruit hard), chlorophyll, and various large organic molecules. For many fruits, the ripening process begins with the release of ethylene gas, one of the simplest possible hydrocarbons (C₂H₄). This signal activates the genes that produce a host of enzymes that transform the fruit from inedible to delicious.

The acids are broken down, while enzymes called amylases convert starch into sugar, producing sweetness. Other enzymes break down the pectin, softening the fruit. Still others decompose large organic molecules into smaller volatile ones that are released, often producing a characteristic aroma. Chlorophyll is broken down, and revealed or newly produced pigments give the fruit its ripened color.

Damage such as a wound to the skin of a fruit may trigger the process too early, which explains why my lemon tree drops a few early yellow fruit that usually turn out to be no good inside. And that's why one bad apple really can spoil a whole barrel, by releasing ethylene and triggering undesired ripening of the rest.

As unpicked fruit ripens, a similar process occurs in part of its pedicel--- the stem that attaches the fruit to the tree. This allows it to drop off at the right time for an animal to carry it off and disperse the seeds to new locations. If the fruit is good enough, some social primate might even start cultivating it, propagating it, and spreading it to any place in the world it can grow.

A Walk In The (Palma Sola) Park

Last week we learned about some of the benefits of a “nature experience” such as a walk through a park. One of the best places for such an experience is, of course, our own Palma Sola Botanical Park. And a great time for it would be 11:00 a. m. on Sunday, October 25.

That's when the MRFC is hosting an educational tour through our fruit tree collection as part of the fifth annual Eat Local Week for our two-county area. Here is our event's description page at the website of Transition Sarasota, the organizer of Eat Local Week. Please spread the word to promote our event, and if you can copy and distribute some flyers, they are available on the description page.

Details of all the Eat Local Week events can be found here.

In addition to our Palma Sola tour, two other Eat Local Week events concern fruit tree horticulture in our area. The Tropical Fruit Society of Sarasota will have a fruit tree mini-sale at the downtown Sarasota Farmer's Market on Saturday, October 24. Vendor Steve Cucura will have the new SuperHass avocado, said to be just like the Hass but highly productive in our climate. On Tuesday night, October 27, the TFSS monthly meeting will feature Noris Ledesma speaking on jakfruit. I expect that her presentation will be similar to the one she gave to the MRFC some months ago, but if you missed that one, or just want a refresher, this is the opportunity.

Many other Eat Local Week events are of interest to plant lovers. Geraldson Community Farm--- which adjoins Palma Sola Park to the south--- holds its Fall Harvest Fest on October 24. There will be not just one, but three plant walks to learn about wild native plants, including this one directed by clinical herbalist Bob Linde at Palmetto's Emerson Point Preserve on Thursday, October 29. The plant walks require pre-registration for a limited number of openings, so don't wait until the last minute.

With a diverse slate of 28 events, Eat Local Week has something for everyone: fruit trees, school gardens, cooking, aquaculture at Mote Aquarium, charity harvesting for the food bank, tasting local craft beers, and more. It's yet another benefit of living here on Florida's Suncoast.

A Walk In The Park

Writers have been praising the joys of experiencing nature for a while now. Aristotle wrote that “In all things of nature there is something of the marvelous.” More to the focus of today's post, nineteenth-century environmentalist John Muir said that “In every walk with nature one receives far more than he seeks.” Speaking of walks, playwright Noel Coward said “I like long walks, especially when they are taken by people who annoy me.” But now we're wandering off-topic.

OK, so it's not news that a walk out in nature is a pleasure, but a recent New York Times article headlined as How Walking In Nature Changes The Brain tells about some recent efforts by scientists to pin down just why it is that a stroll through the grove can be such a balm for the spirit.

Stanford University graduate student Gregory Bateman and four collaborators recently published an article in the Proceedings of the National Academy of Sciences that describes more precisely what happens in our brains during a “nature experience”, as they call it.

As summarized in the Times article, the key is the mental state we call brooding--- the unhealthy internal fretting over what is wrong with us, with our lives, and so on. Physiologically, brooding is strongly associated with increased activity of a region of the brain called the subgenual prefrontal cortex.

The scientists divided their research subjects into two groups. Each member of the lucky group took a solitary 90-minute walk through a quiet, parklike area of the Stanford campus, with no iPods or other distractions allowed. The others took a similar stroll along a noisy highway.

A post-walk questionnaire showed that the forester hikers were not dwelling as much on the negative aspects of their lives as the road walkers. This was corroborated by a post-walk brain scan showing less blood flow to the subgenual prefrontal cortex in the first group.

The scientists are the first to admit that many questions remain about just what is going on here, let alone about how much walking under what conditions gives the beneficial effect. I do applaud their work, and especially their choice of subject matter, but a description of the brain chemistry that goes on when one walks in the woods--- or eats a mango--- doesn't really get at the experience itself. Let the science proceed, but let's not leave aside the poets.

Florida Hills

I live on the top of a hill. It's a Florida hill, about two feet higher than the surrounding land, made of fill trucked in to meet building code requirements. In fact much of the eastern half of my property is hilly, with a gradient of at least one foot from north to south, and a central valley that became a 3-inch deep lake for a while in the summer of 2013.

OK, so it's not much by the standards of most locales, but I've observed that even gentle slopes and the almost imperceptible peaks and valleys of a “flat” area can have a horticultural impact. When the soil on the slope down from my house is dry, or even when it isn't, the lion's share of the heavier rainfalls runs off. Where there is turf, more is captured. But turf is a tough competitor best kept away from favored trees--- just lift a shovelful and you'll generally find the soil bone dry below its tightly-packed roots. Either way, precious little water finds its way to tree-root level.

To remedy this, I took to terracing those of my slope-dwelling plants that needed frequent watering, or seemed to languish for no apparent reason. Often, the results have been dramatic. To the left is a young Bougainvillea glabra--- the upright growing and less-thorny Tree Bougainvillea--- that I nearly pulled out after it defoliated last fall and went well into spring with no sign of activity. In fact, the shovel was in my hand when I noticed a few low buds, so instead I used the shovel to lay in some concrete edging and level off the surrounding soil. Besides giving rain or hand watering a better chance to soak in, the little wall retains a thicker layer of mulch, with its attendant benefits. As you can see, the effect has been dramatic, with the vigorous bloomer now on its way to being a showpiece.

I prefer the 2-by-6-inch “scalloped” edging with three decorative arches on one side, but I like to put that side in the ground to produce a nice, straight look, and to make it easier to clear off intruding grass and weeds. It comes in 2-foot straight sections and in 90-degree turns. It may be a bit hard to find--- in the north half of Sarasota I know only one place that sells it--- and it costs a few bucks more. The smaller, lighter product found in big-box home-and-construction stores would work, but I think the extra height and thickness cut the maintenance effort and enable one to keep a thicker layer of mulch around the plant. In sandy soil, either kind is easy to lay in (unless oak tree roots are in the way), but I do need to use a level to keep the top even.

To the right is an Irwin mango planted last May on a high spot. Once its tap root is established, it won't need any help staying hydrated, but this mini-terrace made it very easy to get the four-footer established.

To the right of Irwin is part of a self-maintaining stand of Sauropus androgynus (Katuk), an excellent-tasting perennial green. I just clip a bit of this and scissor the leaves directly onto a salad, for flavor and nutritional diversification.

I could go on and on, but let's just close with a couple more photos. First, Cogshall and Fairchild mangos and a Raggedy Ann copperleaf on the slope by the driveway, all looking happy as can be with no irrigation, and second, a non-irrigated green sapote tree behind the house. Even here in Flatland, terracing can be a useful technique.