Pond Apple in Seabranch
Today John Bradford* and George Rogers** continued a
year-long botanical exploration of Seabranch State Park by slogging up a muddy
creek straight out of Jurassic World amid eight-foot sagittarias, jungle-sized
grasses and sedges, and leather ferns fit for a dinosaur. We were seeking an old friend from that creek,
Eelgrass (Vallisneria americana),
but not a blade in sight. Still there
were plenty other good things to see. Rounding
a bend, John said, “oh look, pond apples have knees.” Lining the creek are some of the biggest
gnarliest pond apples we know locally, reminiscent of 1920ish black and white
photos by botanist John Kunkel Small when uncut pond apples ruled. Those in Seabranch aren’t that size, but they’re
headed that way.
We like tree’s knees because we’ve scratched out heads over
bald cypress knees. Pond apple knees differ.
Those we saw are arched roots, and they were predominantly hollow, or with
ultra-soft tissue “aerenchyma” at the core.
Thus they are far more credible air pipes than cypress knees, often split
open, which may be pathological, or may be direct ventilation. Tree
physiologists have suggested the massive sizes of the pond apple root systems to compensate for the sacrifice of so much root tissue to ventilation. The trunk makes external roots that dangle
and rejoin the main trunk. And to enhance the overall gnarliness there are burls.
Pond apple (Annona glabra) is well known for its soft wood, even being classified
in a unit called “Section Phelloxylon,” which means “cork wood.” Let’s
run with that a moment. What now follows is specific speculation based on
factual generalities:
A lot of swampy trees have soft wood. Trees living with wet-dry water availability tend toward disproportionate amounts of soft wood. This is especially so of those making most of their new leaves during the dry season. The water they need for that wet job during dry times is partly stored in the wood.
A lot of swampy trees have soft wood. Trees living with wet-dry water availability tend toward disproportionate amounts of soft wood. This is especially so of those making most of their new leaves during the dry season. The water they need for that wet job during dry times is partly stored in the wood.
Pond apple, including the one in my back yard, makes most of
its new leaves and big fleshy flowers in springtime before the rainy months. To make the boom-bust more challenging, pond
apples often grow in places that are intermittently flooded, and
even periodically salty, both conditions prone to interfere with root water
uptake and probably favoring water-strorage in the wood. The boom-bust of water availability may be
tidal and daily, or sporadic as the creek rises and falls, or seasonal following
dry/wet seasons. As researcher G. Zotz and collaborators*** pointed
out, shallow roots make pond apple especially vulnerable to water shortage
during dry times. In all those cases, the tree needs a water
checking account.
Zotz’s research showed pond apple to have, “a large margin of safety from embolism [internal damage from drying], which may provide protection against rare drought events, or may be an adaptation to brackish mangrove habitats.” I’ll bet water in the corky trunk is a component of the safety margin****.
The big fleshy flowers are among the finest in the swamp, primitively pollinated by beetles. The expensive thick blossoms, fleshy lumpy “apple,” and its large seeds seem to represent the rough tendency of dominant forest species to make a heavy investment in relatively few offspring, giving each a competitive head start (such as large seeds packing plentiful food reserves) in the shaded forest environment. Such as a mature pond apple forest. The fruits and seeds probably disperse largely by floating, although they are animal food too.
The distribution of pond apples is so broad I don’t know where they are “natural” as opposed to introduced. They occur in south Florida, tropical America, and in Asia. The tree was deliberately introduced to Australia as a grafting rootstock; it escaped cultivation there and became an invasive exotic pest…revenge for melaleuca!
Zotz’s research showed pond apple to have, “a large margin of safety from embolism [internal damage from drying], which may provide protection against rare drought events, or may be an adaptation to brackish mangrove habitats.” I’ll bet water in the corky trunk is a component of the safety margin****.
The big fleshy flowers are among the finest in the swamp, primitively pollinated by beetles. The expensive thick blossoms, fleshy lumpy “apple,” and its large seeds seem to represent the rough tendency of dominant forest species to make a heavy investment in relatively few offspring, giving each a competitive head start (such as large seeds packing plentiful food reserves) in the shaded forest environment. Such as a mature pond apple forest. The fruits and seeds probably disperse largely by floating, although they are animal food too.
The distribution of pond apples is so broad I don’t know where they are “natural” as opposed to introduced. They occur in south Florida, tropical America, and in Asia. The tree was deliberately introduced to Australia as a grafting rootstock; it escaped cultivation there and became an invasive exotic pest…revenge for melaleuca!
*Webmaster for this site, photographer, and founder of the Friends of Seabranch. John took all of today’s photos.
**Repulsive swamp creature
***Tree Physiology 17: 359. 1997
**Repulsive swamp creature
***Tree Physiology 17: 359. 1997