THE POD-BEARING TREES
The Locusts--The Acacias or Wattles--Other Pod-bearers
Whenever we see blossoms of the sweet-pea type on a tree or pods of
the same type as the pea's swinging from the twigs, we may be sure
that we are looking at a member of the pod-bearing family,
_leguminosae_, to which herbaceous and woody plants both belong. The
family is one of the largest and most important in the plant kingdom,
and its representatives are distributed to the uttermost parts of the
earth. Four hundred and fifty genera contain the seven thousand
species already described by botanists. Varieties without number
belong to the cultivated members of the family, and new forms are
being produced by horticulturists all the time. This great group of
plants has fed the human race, directly and indirectly, since the
First Man appeared on earth. Clovers, alfalfas, lentils, peas, beans
yield foodstuffs rich in all the elements that build flesh and bone
and nerve tissues. They take the place of meat in vegetarian
dietaries.
Besides foods, the pod-bearers yield rubber, dyestuffs, balsams, oils,
medicinal substances, and valuable timber. A long list of ornamental
plants, beautiful in foliage and flowers, occurs among them, chiefly
of shrub and tree form.
Last, but not least, among their merits stands the fact that
leguminous plants are the only ones that actually enrich the soil they
grow in, whereas the rest of the plant creation feed upon the soil,
and so rob it of its plant food and leave it poorer than before.
Pod-bearers have the power to take the nitrogen out of the air, and
store it in their roots and stems. The decay of these parts restores
to the soil the particular plant food that is most commonly lacking
and most costly to replace. Farmers know that after wheat and corn
have robbed the soil of nitrogen, a crop of clover or cow peas, plowed
under when green and luxuriant, is the best restorer of fertility. It
enriches by adding valuable chemical elements, and also improves the
texture of the soil, increasing its moisture-holding properties, which
commercial fertilizers do not.
Seventeen genera of leguminous plants have tree representatives within
the United States. These include about thirty species. Valuable timber
trees are in this group. All but one, the yellow-wood, have compound
leaves, of many leaflets, often fern-like in their delicacy of
structure, and intricacy of pattern. With few exceptions the flowers
are pretty and fragrant in showy clusters. The ripening pods of many
species add a striking, decorative quality to the tree from midsummer
on through the season. Thorns give distinction and usefulness to
certain of these trees, making them available for ornamental hedges.
THE LOCUSTS
Three representatives of the genus _robinia_ are among our native
forest trees. They are known in early summer by their showy, pea-like
blossoms in full clusters, and their compound leaves, that have the
habit of drooping and folding shut their paired leaflets when night
comes on, or when rain begins to fall. The pods are thin and small,
splitting early, but hanging late on the twigs.
=The Black Locust=
_Robinia Pseudacacia_, Linn.
The black or yellow locust is a beautiful tree in its youth, with
smooth dark rind and slender trunk, holding up a loose roundish head
of dark green foliage. Each leaf is eight to fourteen inches long,
of nine to nineteen leaflets, silvery when they unfold, and always
paler beneath. In late May, the tree-top bursts into bloom that is
often so profuse as to whiten the whole mass of the dainty foliage.
The nectar-laden, white flowers have the characteristic "butterfly"
form, the banner, wings, and keel of the type pease-blossom. (_See
illustration, page 198_). The bees lead the insect host that swarms
about them as long as a locust flower remains to offer sweets to the
probing tongues. Cross-fertilization is the advantage the tree gains
for all it gives. The crop of seeds is sure.
The angled twigs of the black locust break easily in windy weather.
The rapid growth of the limbs spreads the narrow head, and its
symmetry is soon destroyed, unless the tree grows in a sheltered
situation. An old locust is usually an ugly, broken specimen,
ragged-looking for three-fourths of the year. The twigs look dead,
because their winter buds are buried out of sight! The bark is dull,
deeply cut into irregular, interlacing furrows, roughened by scales
and shreds on the ridges. In winter the pods chatter querulously,
as the wind plays among the tree tops.
The black locust is found from Pennsylvania to Iowa, and south from
Georgia to Oklahoma. The lumber is coarse-grained, heavy, hard, and
exceptionally durable in contact with the soil or water. This makes
it especially adaptable for fence posts and boat bottoms. Crystals,
called _raphides_, in the wood cells, take the edges off tools used
in working locust lumber. Yet it is sought by manufacturers of mill
cogs and wheel hubs, and railroad companies plant the trees for
ties.
The locust-borer has ruined plantations of this tree of late years,
and trees in the woods have become infested except in mountainous
regions not yet reached by the pest. Trees become distorted with
warty excrescences and the lumber is riddled with burrows made by
the larvae. Until the entomologist finds a remedy in some natural
parasite of the locust-borer, the outlook for locust culture seems
dark enough. No insecticide can reach an enemy that hides in the
trunk of the tree it destroys.
=The Clammy Locust=
_R. viscosa_, Vent.
The clammy locust has beautifully shaded pink flowers in clusters,
each blossom accented by the dark red, shiny calyx, and the
glandular exudation of wax, that covers all new growth. A favorite
ornamental locust, this little tree has been widely distributed in
this and other temperate countries of the globe. Its leaves are
delicately feathery, with the dew-like gum brightening them, as it
does also the hairy, curling pods that flush as they ripen. In
winter the twigs are ruddy. The trees grow wild on the mountains of
the Carolinas and nowhere else.
=The Honey Locust=
_Gleditsia triacanthos_, Linn.
The honey locust is a tall handsome flat-topped tree, with stiff
horizontal, often drooping branches, ending in slim brown polished
twigs, with three-branched thorns, stout and very sharp, set a
little distance above the leaf scar of the previous season.
Occasionally a thornless tree occurs.
Inconspicuous greenish flowers, regular, bell-shaped, appear in
elongated clusters, the fertile and sterile clusters distinct, but
on the same tree. The leaves are almost full-grown when the blossoms
appear. Their feathery, fern-like aspect is the tree's greatest
charm in early June. When the pods replace the flowers they attract
attention and admiration as their velvety surfaces change from pale
green to rose and they curve, as they lengthen, into all sorts of
graceful and fantastic forms. The sweet, gummy pulp of the honey
locust pods is considered edible by boys, who brave the thorns to
get them. As the autumn approaches, the pulp turns bitter, and dries
around the shiny black seeds. The purple pods cling and rattle in
the wind long after the yellow leaves have fallen. One by one, they
are torn off, their S-curves tempting every vagrant breeze to give
them a lift. On the crusty surface of snowbanks and icy ponds, they
are whirled along, and finally lodge, to rot and liberate the seeds.
It takes much soaking to prepare the adamantine seeds for sprouting.
The planter scalds his seed to hasten the process. Nature soaks,
freezes, and thaws them, and thus the range of the honey locust is
extended.
In the wild, this tree is found from Ontario to Nebraska, and south
to Alabama and Texas. It chooses rich bottom lands, but is found
also on dry gravelly slopes of the Alleghany Mountains. Trunks six
feet in diameter are still in existence, preserved from the early
forests of the Wabash Basin in Indiana. They tower nearly one
hundred and fifty feet above the ground, and their branches are a
formidable array of thorns (_see illustration, page 198_), that have
grown into proportions unmatched in trees of slender build and fewer
years. Such a veteran honey locust is one of the most picturesque
figures in a winter landscape.
Honey locust wood is hard, coarse-grained, heavy, and durable in
contact with water and soil. It is made into wheel-hubs,
fence-posts, and fuel. In all temperate countries this species has
been used as a shade and ornamental tree and as a hedge plant.
=The Kentucky Coffee Tree=
_Gymnocladus dioicus_, K. Koch
The Kentucky coffee tree is the one clumsy, coarse member of a
family that abounds in graceful, dainty species. Its head is small
and unsymmetrical, above a trunk that often rises free from limbs
for fifty feet above ground. The branches are stiff and large, bare
until late spring, when the buds expand and the shoots are thrown
out. The leaves are twice compound, often a yard in length and half
as wide; the leaflets, six to fourteen on each of the five to nine
divisions of the main rib. No other locust can boast a leaf
numbering more than one hundred leaflets, each averaging two inches
in length. When the tree turns to gold in autumn, it is a sight to
draw all eyes.
The flower spray is large, but the flowers are small, imperfect,
salver-form, purplish green--the fertile ones forming thick, clumsy
pods that dangle in clusters, and seem to weigh down the stiff
branchlets. The fresh pulp used to be made into a decoction used in
homeopathic practice. The ripe seeds were used in Revolutionary
times as a substitute for coffee. How the pioneer ever crushed them
is a puzzle to all who have tried to break one with a nut-cracker.
In China the fresh pulp of the pods of a sister species is used as
we use soap.
The wood is not hard, but in other respects it resembles other
locust lumber. It is sometimes used in cabinet work, being a rich,
reddish brown, with pale sap-wood.
The range of the coffee tree extends from New York to Nebraska, and
south through Pennsylvania, Tennessee and Oklahoma, with bottom
lands as the tree's preference. Nowhere is this species common.
Occasionally, it is planted as a street tree, in this country and
abroad.
=The Redbud=
_Cercis Canadensis_, Linn.
The redbud covers its delicate angled, thornless branchlets with a
profusion of rosy-purple blossoms, typically pea-like, before the leaves
appear. The unusual color, so abundant where little redbuds form
thickets on the outskirts of a woodland, leads to a very general
recognition of this tree among people who go into the April woods for
early violets. It vies with the white banner of the shad-bush, in doing
honor to the spring. Later, the broad heart-shaped leaves cover and
adorn the tree, concealing the dainty tapering pods that turn to purple
as the polished leaf blades, unmarred by insect or wind, change from
green to clear yellow before falling.
[Illustration: _See page 159_
SERVICE-BERRY IN BLOSSOM
The flowers appear in April, before the leaves]
[Illustration: _See page 161_
THE HACKBERRY
Leaves, berries, and (A) pistillate and (B) staminate flowers]
Tradition has given this charming little locust tree the name,
"Judas-tree," from its European cousin, rumored to have been the one
upon which the choice of Judas fell when he went out and hanged
himself. It is an unearned stigma, better forgotten, for it does
prejudice the planter against a tree that should be on every lawn,
preferably showing its rosy flowers against a bank of evergreens.
Its natural range extends from New Jersey to Florida and west from
Ontario to Nebraska and southward. The largest specimens reach fifty
feet in height in Texas and Arkansas, in river bottom lands, and in
the Southwest the tree is an abundant undergrowth--making a
beautiful woodland picture in early spring.
=The Yellow-wood=
_Cladrastis lutea_, K. Koch.
The yellow-wood was named by the wife of a pioneer, surely, for she
soaked the chips and got from them a clear yellow dye, highly prized
for the permanent color it gave to her homespun cotton and woolen
cloth that must have gone colorless, but for dyestuffs discoverable
in the woods.
The satiny grain of the wood, and its close hard texture, commended
it to the woodsman, who used it for gun stocks. But the tree is too
small to be important for the lumber it yields.
In winter the smooth pale bark of the "Virgilia," as the nurseryman
calls it, reminds one of the rind of the beech. The broad rounded
head, often borne on three or more spreading stems, is formed of
drooping graceful branches, ending in brittle twigs. Summer clothes
these twigs with a light airy covering of compound leaves, of seven
to eleven broadly oval leaflets, on a stalk less than a foot in
length. In autumn, the foliage turns yellow.
White flowers, pea-like, delicate, fragrant, in clusters a foot
long, and so loose that the flowers seem to drip from the twig ends,
drape the tree in white about the middle of June, when the young
leaves show many tints of green to form a background for the
blossoms.
This is the supreme moment of the year for one of the most charming
of trees, in any park that cherishes one of these virgilias. In the
wilds of eastern Tennessee, northern Alabama, and central Kentucky
the species is found in scattered places. But the wild trees have
scant food and they show it. The full beauty of the species is seen
only in cultivation, as one sees it in the Arnold Arboretum, and in
private gardens near Boston. Even the little pods, thin, satiny
pointed, add a harmonious note of beauty; their silvery fawn color
blending with the quiet Quaker drab worn by the tree all winter.
Fortunately, this hardy beautiful park tree is easily raised from
seeds and from root cuttings. It thrives on soil of many different
kinds. It has no bad habits, no superior, and few equals among
flowering trees.
THE ACACIAS, OR WATTLES
Australia has contributed to southern California's tree flora a
large number of forms of the acacia tribe, shrubs and trees of
great variety and beauty of flowers and evergreen foliage. They are
hardy and perfectly at home, and are planted in such profusion as to
be the commonest of all street and ornamental trees. The leaves are
set on a branching pinnate stem, making them "twice compound" of
many tiny leaflets, fascicled on the sides of the twigs, alternate
on the terminal shoots of the season. The lacy, fern-like foliage of
most acacias would justify the planting of them for this trait
alone. But the abundant mass of bloom usually overwhelms the
tree-tops, obscuring the foliage with a veil of golden mesh.
Sometimes white, but oftenest yellow, the individual flowers are
very small; but they crowd in button-like heads or elongated spikes,
set close in axillary clusters. In their native woods these trees
flower much less freely than in the land of their adoption. The
curling pods are in most species and varieties ornamental, as they
pass through many color changes before they finally discharge their
seeds.
Acacias compose a genus of four hundred species, and an untold and
constantly increasing number of cultivated varieties. The continent
of Australia has the greatest representation of native species.
Others belong to Africa--tropical, northern, and southern regions.
Asia, in its warmer southern territory, and in southwestern China,
has many native acacias. Tropical and temperate South America, the
West Indies, Central America, Mexico, the southwestern region of the
United States, and the islands of the South Pacific, all have
representatives of this wonderful and far-scattered genus. There is
no country interested in horticulture that does not grow acacias as
ornamental shrubs and trees, even if they must be grown under glass
the year round. In southern England the acacias, grown in open
ground, and known as "tassel trees," attain good size.
Valuable lumber, tanbarks, dyes, perfumes, and drugs are yielded by
acacias. Gum Arabic is the dried sap of several oriental species,
particularly, _Acacia Arabica_, Linn. of Egypt and southern Asia.
As a rule, acacias have slender branches armed with spines. Often
these are too small to attract notice, or to make the species useful
as a hedge plant. All spines are modifications of the stipules at
the base of leaf or leaflet. Thorns, however, are modified twigs,
strong, stiff and sharp, often branched. The honey locust shows true
thorns, not spines or prickles. The armament of canes of blackberry
is only skin deep. This means of defence is best called "prickles."
=The Black Acacia=
_Acacia melanoxylon_
The black acacia, called at home in Australian woods, the
"blackwood-tree," for its black heart-wood, is a familiar street and
shade tree in California. In narrow parkings it is likely to
surprise the planter by outgrowing in a few years the space allotted
to it, and upheaving both cement walk and curb, by the irresistible
force of its thick roots. It is one of the large timber acacias, and
even in the cool climate of England reaches fifty feet.
In suitable situations in California it grows much higher, and its
compact conical head of dense evergreen foliage, gives abundant
shade at all seasons. The flowers are white or cream-colored,
lightening the yellow-green of the new shoots and the dull, opaque
of the older leaves, with abundant clusters in earliest spring. The
succeeding fruits are curling thin pods that hang in brownish
sheaves, giving the tree a rusty look. Each seed is rimmed with a
frill of terra cotta hue that serves as a wing for its flight, when
detached by the wind. The roots send up suckers and the seeds are
quick to grow. So any one can have black acacias with little trouble
or expense. Its shedding of leaves and pods makes much litter,
however, a trait sometimes overlooked which seriously diminishes its
desirability as a street and shade tree.
=The Silver Wattle=
_A. dealbata_
The silver wattle of nursery catalogues is named for its abundant,
silvery-pubescent, feathery foliage. Its flowers--fluffy golden
balls, small but abundant--make this a wonderfully showy tree.
Sea-green and turquoise-blue leaves, with abundant canary-yellow
bloom, are traits of many different acacias in cultivation, all of
which are rapid growers, and soon repay the planter who wants quick
results. From being mere ornaments they rise to the stature of shade
trees, and merely multiply the charms that made them admired when
young. Varieties with sharp spines are employed as hedge plants.
Curious leaf forms and unusual, edgewise position of the foliage,
make us wonder at some of the glorious "golden wattles" and
"knife-leaved acacias," that bring us glimpses of the forests of
Australia and other strange far countries.
OTHER POD-BEARERS
=The Mesquite=
_Prosopis juliflora_, DC.
The mesquite or honey pod is one of the wonderful plants of the arid
and semi-arid regions from Colorado and Utah to Texas and southern
California. At best it is a tree sixty feet high along the rivers of
Arizona. In the higher and more desert stretches it is stunted to a
sprawling shrub, with numerous stems but a few feet high. Its leaves
are like those of our honey locust but very much smaller, and the
tree furnishes little shade. The bark of the trunk is thick, dark
reddish brown, shallowly fissured between scaly ridges. In winter
the tree looks dead enough, but the young shoots clothed with tender
green bring it to life in early spring, and the greenish fragrant
flowers, thickly set in finger-like clusters, appear in successive
crops from May to July. These are succeeded by pods four to nine
inches long in drooping clusters, each containing ten to twenty
beans.
Not its beauty of leaf and blossom but its usefulness is what makes
this tree almost an object of worship to desert dwellers, red men
and white. The long fat pods supply Mexicans and Indians with a
nutritious food, green or ripe. Cattle feed upon the young shoots
and thrive, when other forage is scant or utterly lacking. The fuel
problem of the desert is solved by the mesquite in a way that is a
great surprise to the newcomer. His sophisticated neighbor takes
him on a wood-gathering expedition. Stopping where a shrubby
mesquite sprawls, he hitches his team to a chain or rope that lays
hold of the trunk, and hauls the plant out by its roots. And what
roots the mesquite has developed in its search for water! There is a
central tap root that goes down, down, sometimes sixty feet or more.
Secondary roots branch out in all directions, interlock, thicken,
and form a labyrinth of woody substance, in quantity and quality
that makes the timber above ground a negligible quantity. This wood
is cut into building and fencing materials--two great needs in the
desert. The waste makes good fuel, and every scrap is precious.
Posts, railroad ties, frames for the adobe houses, furniture,
fellies of wheels, paving blocks, and charcoal are made of this
wonderful tree's root system. A gum resembling gum-arabic exudes
from the stems.
=The Screw-bean=
_P. pubescens_, Benth.
The screw-bean or screw-pod mesquite is a small slender-trunked tree
with sharp spines at the bases of the hoary foliage. The marked
distinction between this species and the preceding one is in the
fruit, which makes from twelve to twenty turns as it matures, and
forms when ripe a narrow straight spiral, one to two inches long;
but when drawn out like a coiled spring the pod is shown to be more
than a foot in length. These sweet nutritious pods are a most useful
fodder for range cattle, and the wood is used for fencing and fuel.
This tree grows from southern Utah and Nevada through New Mexico and
Arizona into San Diego County, California, western Texas and
northern Mexico.
=The Palo Verde Acacia=
_Cercidium Torreyanum_, Sarg.
The palo verde is another green-barked acacia whose leaves are
almost obsolete. Miniature honey-locust leaves an inch long unfold,
a few here and there in March and April, but they are gone before
they fully mature, and the leaf function is carried on entirely by
the vivid green branches. Clustered flowers, like little yellow
roses, cover the branches in April, and the pointed pods ripen and
fall in July.
In the Colorado desert of southern California, in the valley of the
lower Gila River in Arizona, on the sides of low canyons and on
desert sandhills into Mexico, this small tree, with its multitude of
leafless, ascending branches, is one of the brightest features on a
hopelessly dun-colored landscape.
=The Jamaica Dogwood=
_Icthyomethia Piscipula_, A. S. Hitch.
The Jamaica dogwood is a West Indian tree that grows also in
southern Florida and Mexico. It is one of the commonest tropical
trees on the Florida West Coast from the shores of Bay Biscayne to
the Southern Keys. The leaves are four to nine inches long, with
leaflets three to four inches in length, deciduous, vivid green,
making a tree fifty feet high an object of tropical luxuriance. Its
beauty is greatly enhanced in May by the opening of the pink,
pea-like blossoms that hang in drooping clusters a foot or more in
length. The necklace-like pods are frilled on four sides with thin
papery wings.
The wood of this tree is very durable in contact with water, besides
being heavy, close-grained, and hard. It is locally used in
boat-building, and for fuel and charcoal. All parts of the tree, but
especially the bark of the roots, contain an acid drug of
sleep-inducing properties. In the West Indies the powdered leaves,
young branches, and the bark of the roots have long been used by the
natives to stupefy fish they try to capture.
=The Horse Bean=
_Parkinsonia aculeata_, Linn.
The horse bean or retama, native to the valleys of the lower Rio
Grande and Colorado River, is a small graceful pod-bearing tree of
drooping branches set with strong spines, long leaf-stems, branching
and set with many pairs of tiny leaflets.
The bright yellow, fragrant flowers are almost perennial. In Texas
the tree is out of bloom only in midwinter. In the tropics, it is
ever-blooming. The fruit hangs in graceful racemes, dark
orange-brown in color, and compressed between the remote beans. As a
hedge and ornamental garden plant, this tree has no equal in the
Southwest. It is met with in cultivation in most warm countries.
=The Texas Ebony=
_Zigia flexicaulis_, Sudw.
The Texas ebony is a beautiful, acacia-like tree of southern Texas
and Mexico. One of the commonest and most beautiful trees on the
bluffs along the coast, south of the Rio Grande. Its leaves are
feathery, fern-like, its flowers in creamy clusters, its pods thick,
almost as large as those of the honey locust. The seeds are
palatable and nutritious, green or ripe. Immature, the pods are
cooked like string beans; ripe, they are roasted, and the pods
themselves are ground and used as a substitute for coffee.
The wood is valuable in fine cabinet work, and because it is almost
indestructible in contact with the ground, it is largely used for
fence posts. It makes superior fuel. Besides being more valuable
than any other tree of the Rio Grande Valley, though it rarely
exceeds thirty feet in height, it is worthy of the attention of
gardeners as well as foresters in all warm temperate countries.
Prof. Sargent calls it the finest ornamental tree native to Texas.
=The Frijolito=
_Sophora secundiflora_, DC.
The frijolito or coral-bean is a small, slender narrow-headed tree,
with persistent, locust-like leaves, fragrant violet-blue flowers,
and small one-sided racemes. The pods are silky white, pencil-like,
constricted between the bright scarlet seeds. The tree grows wild in
canyons in southern Texas and New Mexico, forming thickets or small
groves in low moist limestone soil and stream borders. It is a close
relative of the famous pagoda tree of Japan, _S. Japonica_,
universally cultivated; and it deserves to be a garden tree
throughout the Southern states.