Trees of Cloudbridge
Ulmus mexicana (Tirrá,
palo baqueta, Mexican elm)
Description:
One of the
spectacular forest trees of Cloudbridge, having a clear straight
bole, unbuttressed and generally unbranched until near the top,
sometimes nearly 35 m tall -- one of the tallest trees of the area. The
crown is deep, with very dense foliage; almost no light passes through.
Our
first observations were made in June
and July, and on our next visit in December we were shocked to see our
favorite tree denuded, and felt anxious as to its health. A few months
later we were back at Cloudbridge, and with relief, saw that once again
the
tree was in its full leafy glory.
Ecology: The tree is shade
tolerant and grows slowly until a break in the forest allows
it to
reach its full canopy or emergent stature. The
leaves are host to a variety of lichens, and the crotches of branches
are frequently filled with epiphytes -- including strangler figs, which
can often be seen establishing a tangle of roots. One often finds U.
mexicana growing near Clethra mexicana
and Billia colombiana.
They grow in
pre-montane and montane humid forests, with an annual rainfall between
2500 and 4000 mm.
Distribution:
A common canopy tree in the old forest on the western slopes of the
Talamanca range, it is often found on steep slopes alongside rivers and
canyons. On Cloudbridge, a tall example with light-colored bark and
silvery leaves may be seen opposite our house Casa Amanzimtoti, and
others across
from Cloudbridge Falls. Many grow on Cloudbridge North. In Costa Rica,
at medium altitudes of the Central Pacific region, the Tilaran range,
the central volcanic range and the Escazú peaks, as well as the
Talamancas. They are found between 600m and 2000m elevation from Mexico
to Panama.
How
to recognize: Distinctive leaves with much-serrated borders.
Uses: Tirra is not one of the most commonly harvested timber trees
of
Costa Rica
because the trunk is often indented and less useful for lumber. Because
of deforestation, the species is getting scarcer but is
not yet threatened. Apart from at Cloudbridge, few if any are grown in
plantations.
Sources and Links:
INBio description
SysTax
Scientific Information:
Division: |
Magnoliophyta (Flowering plants)
|
Class: |
Magnoliopsida (Dicots)
|
Order: |
Rosales
|
Family: |
Ulmaceae (Elm family)
|
Species: |
Ulmus mexicana
(Liebm.) Planch (alt. name
Chaetoptelea mexicana) |
Photo
Identification Guide: Ulmus
mexicana
(Tirrá, Mexican elm)
Leaves.
Simple leaves, alternate arrangement. Shape is elliptic or ovate.
Edges are serrated. Leaves have petioles. The surface of the leaves are
glossy, with the underside dull.
The
leaves have prominent midribs and veins in
the abaxial surface and have arcuate venation. The
size of the leaves can vary from 3.5 cm to 16 cm in length and 2 cm to
7 cm in width. The petiole of the leaves
can
vary in length from 5 to 10 mm.
|
©Barry Hammel
Missouri Botanical Garden
|
Flowers. Flowers are pale green and
lighter in tone than the leaves, and they flourish between December and
February. |
|
Fruit and Seeds. Fruits have a green-yellowish
tone, are flat, lightly elongated and
dry, and are 6 to 8 mm in length. The
fruits
are all covered with long and straight hairs. There
is one seed per fruit, which is approximately 2 mm in length and of
yellowish and flat configuration. The fruit appears in February and
March.
|
|
Trunk. The tree trunk
is grayish, long and straight and approximately 1 m in diameter for
mature trees. The trunk is characterized
by
demarcated longitudinal indentations all along its length, which makes
it less desirable for the timber industry |
|
Form. A
clear straight
bole, unbuttressed and generally unbranched until near the top, where
the leafy brances spread out into a hemisphere.
|
|
Saplings. Seedlings
and saplings display a characteristic zig-zag stem with well-formed
serrated leaves similar to those of the mature plant.
|
|
Cloudbridge: Bridging
a Costa Rican cloud forest