The Tree (31 page)

The Apocynaceae family is again big and highly various, with around 3,700 species of trees, shrubs, vines, and herbs in 335 genera, again mainly tropical and subtropical, with just a few in temperate lands. Most of the genera contain poisonous species, which, as is the nature of things, are often converted to valuable drugs—none more so than the Madagascar periwinkle
(Catharanthus)
, the source of some of the most effective drugs against leukemia, and
Rauvolfia,
which provides a drug that’s used to treat hypertension. But the Apocynaceae also include some pleasant and quaint ornamentals, including periwinkle
(Vinca)
, oleander
(Nerium)
and the carrion flower
(Stapelia),
a peculiar worm-like succulent whose evil-smelling blooms are pollinated by flies and yet is beloved of collectors (among whose ranks I once was, and perhaps will be again). The trees of the Apocynaceae, all tropical, are often huge and impressive. The genus
Dyera
includes
D. costulata,
of Malaysia and Indonesia, known as jelutong. It stands up to 60 meters tall and yields creamy timber that matures to the color of straw, excellent for sculpting and carving, not least of wooden clogs. It also yields a latex that is extracted for chewing gum—and the process of extraction commonly leads to a fungus infection that colors the timber, which, as in beech, or indeed in blue cheeses, can increase its value. Species of
Aspidosperma
from southeastern Brazil are marketed as rosa peroba. The trees stand around 15 meters tall; the sapwood is creamy yellow, the heartwood rosy red, hard, heavy, very dense, and used for everything from building ships to parquet floors, turnery, and very beautiful veneers.

Best known of all the trees of the Apocynaceae, however, is the frangipani,
Plumeria rubra,
alias the temple tree or pagoda tree, sometimes growing as a small tree up to 6 meters and often as a large bush. The frangipani was imported to India from its native Jamaica, Mexico, and Ecuador. Mrs. Cowen, in
Flowering Trees and Shrubs in India,
writes that with its “pale swollen limbs the tree is in itself no thing of abundant beauty.” But “It claims affection for its sweet-scented flowers which, nearly throughout the year, open, bloom, and fall to lie immaculate on the earth beneath. To both Buddhists and Mohammedans the tree is an emblem of immortality because of its extraordinary power of producing leaves and flowers after it has been lifted from the soil. For this reason it is frequently planted near temples and in graveyards, where daily the fresh, creamy blooms fall upon the tombs. Hindus make use of the flowers in worship and they are frequently given as votive offerings to the gods.” Frangipani finds many uses in medicine, and its yellow-brown and reddish timber, though it comes only in smallish pieces, is easily worked.

Among the 970 or so species (in 84 genera) in the Gentianaceae are the gentians, for which the whole family and order are named. These are not trees but ornamental herbs. Some members of the family are extreme parasites with small leaves and no chlorophyll (showing once again that flowering plants have a considerable predilection for parasitism). Some are pleasant shrubs. Many provide medicines and flavorings. But there would be precious few significant trees among the Gentianaceae were it not that the Loganiaceae, which is the last family of the Gentianales, has recently been reexamined and reorganized. So the tropical Asian genus
Fragraea
has been transferred to the Gentianaceae from the Loganiaceae, where it traditionally resided; and
Fragraea
includes some significant timber trees, one of which
(F. fragrans)
has particularly huge flowers and is also planted as an ornamental. The plants that remain in Loganiaceae include nothing that need occupy a book on trees.

O
LIVE
, A
SH
, J
ACARANDA
,
AND
T
EAK
: O
RDER
L
AMIALES

Taxonomists have got seriously stuck into the Lamiales this past few years. The order has grown: it now embraces the traditional order Scrophulariales, which included the antirrhinums and foxglove; and subsumes the old Bignoniales, which contained some magnificent trees, as will shortly be described. In addition, there has been much chopping and changing of genera between the different families that made up the original three orders that are now included within the Lamiales. I will not go into details because most of the changes do not involve trees—and I am mentioning all this only to provide continuity with traditional texts. (If you read Heywood, for example, as everyone should, you will find the order Scrophulariales, and you might wonder what happened to it if it wasn’t mentioned here.)

The new-style, expanded Lamiales now includes 17,800 species in 24 families. Nineteen of those families contain mainly herbs, some of which are parasitic, like the serious tropical weed
Striga
and the temperate wayside broomrapes,
Orobanche.
There are many epiphytes (notably in the African violet family, Gesneriaceae) and also some vines and shrubs (the garden favorite
Buddleia
has been imported into Lamiales from its former position among the Gentianales), but at best these families include only a few small trees. Among five of the Lamiales families, though, there are some very significant trees indeed.

The Avicenniaceae family includes
Avicennia,
which is described in the discussion of mangrove swamps in Chapter 11. Until recently,
Avicennia
was sometimes placed within the Rhizophoraceae, alongside what is perhaps the best-known of the mangrove genera,
Rhizophora.
Now it is clear that its resemblance to
Rhizophora
is an example of convergent evolution—two plants with a similar way of life, adopting similar solutions to it.

The Myoporaceae family—about 150 species in four genera from Australia and the South Pacific, with a few in South Africa, southern Asia, and Mauritius—are mainly trees and shrubs. Best known are the highly drought-resistant genus of
Eremophila,
which includes the colorful emu bushes and some useful timber trees, and
Myoporum,
also with some pleasant, aromatic shrubs and some timber trees.

Ecologically and economically, though, the Avicenniaceae and Myoporaceae families are minor. Of supreme importance in all ways is the Oleaceae family. It includes 600 or so species in 29 genera, grows in tropical and temperate climates, and includes vines, shrubs, and trees. The shrubs include privet, lilac, forsythia, and jasmine. The trees include the 60 or so species of ash
(Fraxinus),
and the 20 or so species of olive
(Olea).

The European ash,
Fraxinus excelsior,
is one of the great trees. If it weren’t for human beings changing the landscape so radically, present-day, post–ice age Britain would be covered virtually from end to end with forests of Scotch pine, oak, and mixtures of oak and ash. The timber is creamy white to light brown, sometimes with dark heartwood that is marketed as “olive ash.”
F. americana
is the American or white ash. The timber of both species is wonderfully springy—excellent for oars, tool handles, and baseball bats—and also lends itself to steaming and bending: and so it turns up too in bentwood furniture, umbrella handles, and so on.
F. ornus
is cultivated in Sicily for the sweet gum that it exudes, known as “manna.”

The olive of the Mediterranean,
Olea europaea,
is the species grown for its delectable, oily fruits—not just a treat in those parts but traditionally a staple. The trees are generally small and misshapen, but other olive species from Kenya, Tanzania, and Uganda, such as
O. hochstetteri
and
O. welwitschii,
grow to 25 meters and provide valuable “olivewood”: pale brown with attractive dark, curly streaks; highly resistant to abrasion; and valued for floors, furniture, sculpture, turning, and veneers.

The family Bignoniaceae includes some very important trees—although most of the family are vines and many more are mere shrubs. The 800 species (in 113 genera) are mostly native to South America, but others come from throughout the tropics and subtropics, and a few are temperate. The forty-odd species of
Jacaranda,
from South America, include
J. mimosifolia,
a native of Brazil but grown throughout the tropics and subtropics for its beautiful blue flowers. Jacaranda has fine timber too: pleasantly scented, often patterned with dull purple streaks, and favored for pianos in Egypt, for some reason.
Catalpa
is one of the Bignoniaceae that grows in temperate climes and in Britain is sometimes called the “Indian bean” because its fruits are long pods, although it is neither a bean nor (I believe) Indian. The extraordinary sausage tree,
Kigelia,
has fruits that are indeed like big fat salamis hanging from the rafters of some Italian kitchen, though biscuit-colored. I have seen it in India, and my wish list includes a possible meeting in its native Africa. The tulip tree,
Spathodea campanulata
(not to be confused with
Liriodendron
from the Magnoliaceae), comes from tropical Africa but was introduced to India in the late nineteenth century, both for its shade and for its marvelous masses of scarlet flowers, which earned it the soubriquet of “flame-of-the-forest.” Some Bignoniaceae are useful timber trees.
Paracetoma peroba,
from the coastal forest of Brazil, grows to 40 meters; its pale, golden-olive heartwood is known as white peroba and is highly favored for furniture, boats, floors, and veneers. Even catalpa provides fence posts.

Now comes scope for possible confusion, which I will do my best to ameliorate. In traditional texts you will find two families that have long been thought to be closely related: the Verbenaceae and the Lamiaceae. (Confusion is compounded because the Lamiaceae was formerly known as the Labiatae, and members of the Lamiaceae are still commonly called “labiates,” at least by people like me, in whom old habits die hard.) The Verbenaceae family was named after the perennial
Verbena
and also included
Lippia,
the lemon verbena, and
Lantana,
the South American ornamental that is now the mother of all pests, taking over tropical waysides and forests just about everywhere it has been introduced, and spurned by elephants, which gives it even more scope to grow. The traditional Verbenaceae was best known, however, for
Tectona grandis,
alias teak, which, when both quantity and quality are taken into account, is by far the most valuable of the tropical hardwoods. In the Lamiaceae (formerly Labiatae) were a few big woody plants, including the 57 known species of the genus
Gmelina
from India, Malaysia and Australasia, such as the all-purpose timber tree
Gmelina arborea.
But the Lamiaceae family was best known for its range of culinary herbs: mint, oregano, basil, rosemary, sage, lavender, thyme.

Teak grows slowly; it is traditionally harvested in India at eighty-year intervals.

Of late, however, taxonomists have found that the old-style Verbenaceae was not a clade but more of a mixed bag. Most of its members were more closely related to other families or needed to be placed in their own families. Much more to the point, about two-thirds of the traditional Verbenaceae now seem to belong in the Lamiaceae. So now Verbenaceae is a much less interesting family. It still includes lemon verbena, verbena, and lantana. But the jewel of the family,
Tectona,
now finds itself grouped with mint, thyme, oregano, and the rest in the Lamiaceae. Modern taxonomy makes some strange bedfellows. The Lamiaceae now emerges as a huge and cosmopolitan family with nearly 7,000 species in more than 250 genera.

Teak grows naturally in mixed tropical forests in a range of conditions, although it is generally supposed to prefer a climate with a dry season, as opposed to uninterrupted rain. It grows naturally alongside many other species in forests in India, Myanmar, Thailand, and Laos—although it may not be native to India: Hindu monks may have brought it in from Indonesia in the fourteenth century. There are huge plantations, too, throughout the tropics, not least in Brazil. Some Indian foresters feel that teak, for all its magnificence, is somewhat overplayed: at the start of 2004, to help restore the balance, the director of the Forestry Research Institute in Dehra Dun, Dr. Padam Bhojvaid, organized a conference to refocus attention on some of the other 400 or so Indian species (out of more than 4,000 Indian natives) that have been put to use this past few thousand years. But the attractions of teak are clear. Its timber is strong and durable, enduring the great outdoors without treatment and weathering to a characteristic, sober gray. As a bonus, it is available in long lengths. The Mesopotamians recognized its worth in the third millennium
B.C.
The Europeans came to it somewhat later, in the sixteenth century, and from then on used it to build much of their navies. It is now grown in plantations throughout the tropics, not least in Brazil, and is the subject of huge research endeavors in genetics, tissue culture, and the control of pests and diseases. A particular target is a moth that regularly defoliates the trees—which is disfiguring and also reduces growth rate. By 1998 the total area of teak worldwide was estimated at 69 million acres—although the lion’s share of this was still in natural forest.
Tectona grandis
is the valuable teak. Four other known species
(T. australis, T. hamiltoniana, T. philippinensis, T. ternifolia)
can be ecologically but not economically important locally.