Fairchild’s tropical garden column

Beware the invasive pongam tree

 

Fairchild Tropical Botanic Garden

Once upon a time, a seed sprouted in the corner of a suburban yard. The seedling grew and grew. Soon it overtook all of its neighboring plants and trees as they reached for the sun, competing for its life-giving light.

The man who cares for the yard noticed it when it grew into a sapling, and he wondered what species it could be. He wished the plants he tended would grow so vigorously. The man let the volunteer sapling continue, eager to discover its name.

Only a couple years later, the man noticed a huge tree that seemed to have appeared from out of nowhere, tucked into the same far corner of his yard. “Where did THAT come from,” he pondered. “Well, I’ve always wanted to build a treehouse.” That tree is now the tallest in his yard, out-competing his very tall bamboo and coconut palms.

The tree’s flowers are one of its distinguishing features, clustered into what look like groupings of small shells — like wind chimes you’d buy in the Keys — somewhat similar to the flowers of shell ginger. They are pale purple to a pearly, translucent white, almost like porcelain, and slightly fragrant.

Finding another tree with such flowers, I was able to identify my friend’s volunteer: it’s a pongam tree ( Milletia pinnata, or Pongamia pinnata).

The tree originated in tropical and temperate areas of Asia, including India, Malesia, Japan, Thailand and parts of Australia and Oceania, and it seems almost inevitable that the pongam would make itself at home in South Florida.

Seeds were first introduced into the continental United States by David Fairchild in 1910; he grew a pongam at his home in Coconut Grove. It’s an interesting and beautiful ornamental shade tree, attaining heights of 30 to 50 feet or higher with a slightly drooping, weeping and very wide canopy. Its trunk is fairly short, and starts branching fairly low to the ground — the pongam I’m acquainted with branches about five feet up the trunk.

A few months after the tree flowers, seed pods appear. Green and waxy, they mature to brown with a very tough skin. They must fall to the ground and decay to release the one or two seeds within.

The pongam’s high tolerance for salinity and occasional inundation, as well as its ability to stand up against in high winds, have led to its use along waterways. Indeed, it occurs naturally in such environments in Japan, China, Southeast Asia and India.

The pongam grew in popularity with developers in the late 1980s, mainly because it is fast growing. Initially chosen for planting along the new Metrorail, it was rejected in favor of less-messy plantings; this in turn created a glut of pongams previously slated for public planting. The resulting reduced prices were undoubtedly appealing to developers and landscapers.

Here’s why the pongam is too good to be true: It crowds out our natives and is highly invasive. It reproduces not only by producing hundreds of seed pods, but by sending up root suckers quicker than a mushroom grows after a rainstorm. In addition to the root suckers, dozens of seedlings spread out from its base. The surface roots also travel, sending up more suckers in surprising places far from the parent tree.

The tree is also a bit messy. It is temporarily deciduous, defoliating for about a month in spring. Then it flowers and flowers — and drops the flowers by the thousands everywhere. Most parts of this tree are in some way toxic; the flowers are known to stun or kill fish. You could compost the leaves and flowers, which are quite oily.

I can understand why David Fairchild investigated the pongam: He searched the world for plants that offer something of practical use, such as food, animal fodder, insect and disease resistance, or erosion control.

The pongam’s many uses are legend — in its native range. One of the products derived from its seeds is oil, which is inedible but is being considered for use as a biofuel. Its wood, bark and other derivatives serve multiple uses also, from the prosaic to the ethnobotanical.

Miami-Dade County lists it as a “Controlled Landscape plant,” meaning it may not be planted within 500 feet of native plant communities. Pinelands are listed as especially susceptible to pongam invasion. So if you identify a pongam growing on your property, keep in mind the mess, the suckers, and the running roots. You might remove it — and ideally, replace it with a native.

Kenneth Setzer is writer and editor at Fairchild Tropical Botanic Garden

Read more Home & Garden stories from the Miami Herald

  • Washington Report

    A creative way to reach a home sale

    Interest rate buy-downs, long used by home builders, are gaining traction in the resale market.

  •  
AT HOME for release JULY 2014 BY DESIGN Caption 05: Metallics, particularly gold, continue to draw the eye in home decor. A highly polished brass four-post bed with a padded upholstered headboard is a shout-out to '70s chic. The new London collection mixes tradition and Carnaby panache with surfaces that the company calls a mash-up of golds: shiny (but warm) brass, gold-leafed woods and satiny jewel-box cabinetry. The rivet treatment on the Kent buffed-brass chest of drawers echoes nailheads on the tailored upholstered drum ottoman.

    DESIGN TRENDS

    Practitioners of ‘modern’ design are softening their traditional starkness

    For minimalists, even a whisper of decoration is like a flaw on an otherwise perfect diamond. But one reason that a more modern aesthetic currently is appealing to a broader segment of consumers is because it’s showing a softer side. That may translate to a loosening of form or color — both unabashed and subtle — where something more neutral is expected.

  •  
Crate & Barrel’s Bowery queen bed has drawers underneath for storage

    Interior design

    Need more storage? Might have to sleep on that

    Restoration Hardware’s catalogs might be getting bigger, but its furniture, if you can believe it, is shrinking. In 2012, the retailer responded to growing demand for lighter, leaner pieces by introducing a line of scaled-down furnishings. This year, its Small Spaces catalog is organized by city and residence, such as Los Angeles Bungalow or Boston Brownstone.

Miami Herald

Join the
Discussion

The Miami Herald is pleased to provide this opportunity to share information, experiences and observations about what's in the news. Some of the comments may be reprinted elsewhere on the site or in the newspaper. We encourage lively, open debate on the issues of the day, and ask that you refrain from profanity, hate speech, personal comments and remarks that are off point. Thank you for taking the time to offer your thoughts.

The Miami Herald uses Facebook's commenting system. You need to log in with a Facebook account in order to comment. If you have questions about commenting with your Facebook account, click here.

Have a news tip? You can send it anonymously. Click here to send us your tip - or - consider joining the Public Insight Network and become a source for The Miami Herald and el Nuevo Herald.

Hide Comments

This affects comments on all stories.

Cancel OK

  • Marketplace

Today's Circulars

  • Quick Job Search

Enter Keyword(s) Enter City Select a State Select a Category