Plane tree, Platanus. A large tree which is native to Asia and North America. After the cedar of Lebanon, the plane was the most prized tree of antiquity. The ancients refer to different species of plane which were admired for their stature, size, breadth, and fine foliage, and cite remarkable and memorable events on the subject: poets, orators, historians, naturalists, and travellers all celebrated this tree, and left us with details of the ornamental qualities and usefulness which we still recognize in it today. This tree was known in Greece from the flourishing days of Greek democracy when each citizen was a philosopher: the avenues of the famous portiques where young people assembled for exercise were all planted with planes, which combined utility and pleasure through the cool shade offered by their beautiful foliage. [1] Soon after, in the prosperous days of their empire, the Romans took this tree from Asia and delighted in it, making it the ornament of their pleasure gardens. [2] They spared neither time nor expense on its cultivation, even to the point of deriving pleasure from watering it with wine, which was said to have greatly accelerated its growth. It is thought that the plane was subsequently brought to France, where the greatest lords prized its shade so highly that those who wished to rest under it were obliged to pay them tribute. However, the plane does not seem to have been widespread in our kingdom at this time or to have subsisted for a sustained period. However that may be, the plane tree is presently quite common in Italy, Spain, and England, where it is thought that Lord Chancellor Bacon had the first planes planted in the gardens of his estate at Verulamium. [3] The plane reappeared in France far more recently: the oldest known specimen, in the Jardin du Roi in Paris, may be sixty years of age. However, it is only over the past thirty years or so that a few collectors have begun to import plane seedlings from England, and these have remained concentrated in the small circle of amateur collectors of exotic trees. M. de Buffon is one of the first naturalists to have used planes in garden decoration and has had the satisfaction of seeing them thrive and produce fertile seeds on his estate at Montbard in Burgundy. In this area, successful experiments have been conducted on the propagation of the plane which tend to the spread of plane seedlings in the kingdom. However, the tree was not sufficiently well known to excite widespread curiosity: for this, the example of the prince was required; a substantial number of planes were imported from England for the king and since this time planes have been used increasingly in garden ornamentation. [4]

The plane is highly regarded in Persia where it is accorded a striking preference, less for its ornamental value than for its wider uses. Persians claim that this tree contributes to the purity of the air and the salubrity of the locality. This is what chevalier Chardin reports in his Voyages (Amsterdam, 1711): ‘Planes are the commonest trees in Persia. Persians claim that planes have a natural property which repels plague and other airborne diseases, and affirm that there have been no further contagions in Isfahan, their capital, following the planting of planes in every street and garden’. [5] The plane does indeed exude a pleasant fragrance, which is sweet, balsamic, and faintly perceptible as one approaches. However, it becomes no stronger when one handles the leaves: the assemblage of each part of the tree spreads a scent which becomes widespread and carries over a distance only through the number of seedlings.

The plane naturally forms an upright stem which grows to a great height and becomes proportionately broad. The crown is finely shaped. The colour of the bark varies according to the species, but its texture is always soft and smooth, because it renews itself almost entirely though unevenly each year, periodically and gradually scaling off. The leaves are five-lobed, and differ in shape, size, and depth of green according to the species. At the beginning of May, the tree bears globular heads of male or female flowers. [6] The flowers are formed of a large number of fine, unattractive hairs which are attached to seeds grouped round a hard, ligneous nutlet. There are three, four, or five of these globose fruit-balls along each peduncle, which is six or seven inches long. [7] Each fruit-ball, which is twelve or fourteen lines wide when ripe, contains 500-600 seeds bearing some resemblance to those of the scabious.

This tree has excellent properties: it is easy to propagate, grows rapidly in sites of almost any exposure, and thrives even in mediocre soil. It is very sturdy: when it is full grown it is able to withstand the full force of the wind. It takes again readily following transplantion and may be pruned at any time without detriment. Lastly, it is clean and free from disease, and its leaves are neither attacked nor even touched by insects.

Authors generally agree that the plane should be planted in rich, damp soil, and it is true that it thrives in silt and next to water. However, the soil must not be too heavy, hard, or mixed with clay: I have found that in clayey soil this tree finds it difficult to subsist, grows twice as slowly, and does not produce fine leaves, whereas it grows vigorously and makes the best progress in loose, soft soil, on the banks of canals and streams, and especially on north-facing hillsides, which are not steeply sloped and are steeped in water. Any soil which is substantial, cool, and light is suited to it, even when mixed with sand and gravel. However, while these are the best soil conditions, they are not indispensible: the plane has been found to grow satisfactorily in high, mediocre ground and is not entirely unable to subsist in light soil, even when somewhat dry, provided that it has some depth. It can tolerate the same soil conditions as the lime tree, and has even been successfully substituted for the lime on high ground in cases where the latter failed to thrive or subsist.

There are various methods of propagating the plane: it may be raised from seed, cuttings, layers, and even roots. Raising from seed is the longest, most difficult, and least profitable method. Taking cuttings is the simplest and most suitable method of procuring a large number of young trees, while layering is the best means of making them come on well. Propagating planes from roots is not very profitable, while suckering and grafting are not applicable, since the plane does not grow any rooted suckers from its base and is not compatible with any other tree. When it is seven years of age, this tree begins to bear seeds, which ripen only in January. They are ripe if they part readily from the nutlet when the fruit-ball is pressed gently with one’s fingers. These seeds do not spring up readily or abundantly and less than one tenth of them prosper. What is worse, they do not come true: not only do the leaves differ from those of the mother plant, but there are so many scarcely- perceptible differences in their lobing and depth of colour that barely two seedlings are alike. The uncertain success of the seeds is due firstly to their form: they are enveloped by longish spurs covered with clinging hairs, which prevent the seeds from coming up readily through the soil. Secondly, the seedlings which they produce are so small, slender, and feeble when they first spring up that they are prone to rot in damp soil or burn in direct sunlight, from which they are protected only by careful sowing, and by tending the young seedlings when they spring up. It also follows that these seeds rarely thrive when they are sown in the open ground, and that it is better to sow them in pots or seed trays. To this end, fill the pots to within two inches of the top with good, loose kitchen garden soil half mixed with well-rotted compost from a hotbed. Begin by separating the seeds from each nutlet, which is then discarded. A handful of seeds are needed for each pot: take the necessary amount in proportion to the number of pots one wishes to sow, and mix it with dry, well-rotted manure which has been passed through a fine riddle. Rub this mixture between your fingers for about fifteen minutes, in order to mix the seeds with the soil and detach their clinging hairs. Having carried out this operation with great care in view of its importance, fill the pots with a one-inch layer of this mixture: there is no need to cover it with other soil.

The proper sowing season is from 10-20 April: the seed will come up after three weeks in the space of 6-8 days, following which no further seeds will spring up. The pots should be kept cool by light, frequent watering. As soon as the seeds begin to come up, one should tend the pots even more carefully by sheltering them from heavy rain or watering them lightly in hot weather, according to requirements.

In their first year, the young seedlings will grow to twelve or fifteen inches. They must be overwintered in the orangery and may be planted in a tree nursery the following spring. If they are well tended, they will be ready to be permanently transplanted after four or five years. Planes may be raised from cuttings which will thrive readily: for a new method of preparing these cuttings, see Mulberry tree. In their first year, the cuttings will grow to six or seven feet, and by the following autumn most will have rooted sufficiently to be planted in the tree nursery. After three years, they will be ready to be permanently transplanted, but if they can remain in their original site without detriment one will gain a year.

Layering is a successful means of propagating the plane: it is the quickest, simplest, and most profitable method. Most of the young trees which are raised in this way grow straight, strong, vigorous stems of up to ten feet in their first year, which have often rooted sufficiently to be transplanted the following autumn. If they are left in place, they will grow to fourteen or fifteen feet with a girth of four or five inches in their second year, so that in eighteen months, if we suppose the branches to have been layered in spring, one will have trees which are vigorous, ramose, and ready to be permanently transplanted. To this end, trees which are three or four years of age must be layered entirely. It is true that the layers do not produce saplings of equal strength, but the weaker trees need only one more year to reach the strongest. On the method of layering these branches, see To layer.

This tree, though small, is sturdy when it has been raised from seed, layers, or roots, but not when it has been propagated from cuttings. As these cuttings begin to grow vigorously only in summer and their sap is still flowing well into October, the wood, not having hardened sufficiently, is sometimes damaged by the first autumn frosts, and, what is worse, however little the tips of the saplings have been nipped, the sap becomes corrupted and most of the trees perish entirely. But this accident is rare, and occurs only in mountainous regions, narrow valleys and gorges, and next to water, where frosts are earlier and keener than in the open countryside. Furthermore, the saplings are at risk only in their first year, following which they become just as sturdy as those which have been raised by a different method.

Planes take root again readily following transplantation because they put out good, branching roots. Spring is the correct season for this operation, which must be begun early and as soon as the ground is workable, at the end of February or the beginning of March. Planes may be transplanted in autumn, provided that the ground is not damp and that one is not planting very young trees, which may be damaged by a harsh winter, though this can be obviated by covering the stems of the saplings with straw. The plane may be transplanted successfully even when it is old and full grown: this has been tested on trees which were as thick as a leg and which thrived. With regard to the shape of the planting holes and the method of planting, one need only follow the same precautions which are taken when planting elms and limes.

This tree may be pruned at will and in all seasons: one may even lop the stout branches without detriment. However, its shoots are not slender enough to be pruned with the large billhook, which is moreover unsuitable for use on large-leaved trees during the summer. [8] One must consequently use the pruning knife. The more one prunes a plane, the more it will thrive: this succour is even necessary in order to make it ramose from the start, because it has a tendency to shoot up too vigorously when young. Consequently, whether the planes are destined to form allées, quincunxes, salles de verdure, etc., one must prune the front and back branches for several years, by shortening those which shoot too vigorously to within six inches or one foot of the alignment. In other words, one must train these trees into tall palissades on stems of eight or ten feet. This form of cultivation is vital to planes: if it is neglected, the trees will be less attractive. One is frequently obliged to prop planes in order to make them grow upright and support them when they are young, but this practice has two drawbacks: the ties strangle the trees promptly, and the wind, which holds much sway over large leaves, breaks the stems above the crutches. One must visit and change the ties two or three times over the summer and use big, strong crutches which should be at least six feet taller than the tree, so that the main stems can be secured to them as they grow. As soon as the trees are able to support themselves, the crutches, which would then be detrimental, must be removed.

Planes are upright rather than spreading, but their roots are rarely taprooted. In avenues or allées, these trees may be spaced at intervals of fifteen or twenty feet, depending on the soil condition and on how many of them one wishes to enjoy. In quincunxes and salles de verdure, they must be planted more closely, at intervals of twelve feet, since the main purpose of such layouts is to provide shade.

I have thus far said little about grafting the plane tree, to which I will now return in order to destroy some of the myths perpetrated by a number of ancients writing on agriculture whom some moderns have revered. These authors praised the wonders which grafting could work on the plane: if they were to be believed, grafting could enable this tree to bear apples, cherries, or figs. However, nature does not permit such incompatible alliances, and it has been ascertained by a number of experiments that of all trees the plane is perhaps the least suited to being used as a rootstock: not only do the fruit trees which I have just mentioned fail to take again, but, even more surprisingly, shield-buds taken from and grafted on to the same plane do not thrive, and, moreover, a shield-bud taken from a fig and grafted on to a plane will make the plane perish entirely the following winter, so much does the sap of each tree differ. [9]

It is still almost impossible to determine the precise properties of plane wood with regard to its strength, durability, and uses, since broad trees employed as timber would be required for testing and judging. All we know at present is that plane wood is white, quite compact, somewhat pliable, and of medium strength, and that although it is compact and heavy when green, it loses much of its weight in drying. It is as hard as beech wood and between oak and beech wood for quality. It has been affirmed that the Turks use it for shipbuilding, and it is even more certain that Canadians use American plane wood for cartage. [10]

1. Oriental plane. [11] This species, which was the first to be discovered, has been the subject of many éloges but is far from being the most beautiful or gaining the preference by its other qualities. Its bark is browner, its branches more ramose, its leaves smaller, more lobed, and of a darker green, and it grows twice as slowly as the other two planes.

The oriental plane forms a prodigiously tall, broad, upright stem and a beautiful crown, full of broadly-spreading branches which provide much shade. The russet bark remains smooth and uniform even on old trees: it gradually separates from the stem and falls in plates resembling patches of leather. The dark-green leaves are deeply five-lobed in the shape of an open hand and are medium sized, thick, and firm: unfortunately, the tree retains them throughout the winter, even when they are shrivelled. From a distance, the oriental plane resembles the oak.

2. American plane. [12] This tree is widespread in Louisiana, in most of the English possessions, and in the southern regions of Canada, where it attains a prodigious height and breadth. However, it is most commonly found in low-lying areas and on riversides. It is the most beautiful species of plane and the most conspicuous tree with which a large garden may be ornamented. It naturally forms an upright, well- proportioned stem and its branches, which grow and hold themselves at an upward angle, form a beautiful crown. The attractive, yellow-green bark is smooth and even. The leaves are firm, smooth, and glossy: they are more broad than long, their shape is as pleasant as it is singular, and they are of the finest green. The leaves can be up to one, and sometimes 1½ feet wide, but are generally 8-9 inches wide. The American plane is one of the fastest-growing trees: there is scarcely any other tree apart from the Carolina black poplar which grows more promptly. At present in 1761, one may in M. de Buffon’s gardens (to which we have already alluded) see a large allée formed of this species which was planted twelve years ago, and of which most of the trees are 38-40 feet high with an average girth of 2½ feet, even though these gardens are on top of a hillock where the soil is dry, light, and shallow. M. de Buffon’s trees yield fertile seeds each year, and in Chelsea, England, there were planes of this strength in 1728.

This plane is suitable for forming avenues, allées, quincunxes, salles de verdure, etc. It gives beautiful cover, and provides much shade and coolness. It is clean and not subject to attack by insects, and its foliage, being of a soft, bright, glossy green, is splendidly decorative throughout the summer and for most of autumn.

3. Maple-leaved plane. [13] This tree resembles the American more closely than the oriental plane but lacks the beauty of the former.

Given that the seeds of the plane do not come up readily and so many attempts to raise it from seed have failed, it has for a long time been maintained that the seeds were at fault, and that French seeds were infertile while imported seeds were defective. However, I have had seeds from various countries sown over the past ten years, and not one of them has failed: moreover, because they have not come true, they have shown great variety in their leaves, bark, growth, and bearing. The oriental plane seeds have produced seedlings with a grey bark, broader wood, a more rapid growth, and leaves which are larger, less deeply lobed, and sometimes seven- rather than five-lobed. Beyond these broad differences, there are almost as many subtle variations as there are seedlings. The American plane seeds, on the other hand, have produced seedlings with barks which are russet, grey, reddish, etc. Their wood is slenderer and the internodes are closer. Some have buds which are very obtuse, while on others the buds are very acute. They generally grow more slowly. Their leaves are smaller and of different shades of green: they may be dull or glossy. The seedlings are frequently more lobed, and sometimes less deeply lobed and only three-lobed. In short, the seeds of the American plane produce so many subtle variations that it is impossible to describe them, and, what is even more striking, new modifications arise each year. These leaves always retain the broad outline of the plane leaf but with infinite variations. If Nature has so many means of varying her productions, how much more varied would they be were we to sow these seeds in different climates and soil conditions!

Of these cultivars, there are three which I consider most worth propagating.

Seven-lobed oriental plane: its leaves are larger than those of the oriental plane; they are finely dentate and of a beautiful green. [14]

American plane with branching leaves. [15] This tree, though lacking the beauty of the mother plant, has a striking appearance which causes it to differ markedly from other cultivars. Apart from differences in the bark which is grey and somewhat rough, the colour of the foliage which is pale and dull, and the growth which is less prompt, the leaves curl inwards on either side, concealing all but three leaf tips, so that they bear some resemblance to the shape of a goosefoot.

American plane with few leaf lobes. [16] This is the most beautiful cultivar which I have raised from seed. It is true that its leaves are smaller than those of the mother plant and that it grows more slowly, but this cultivar is just as decorative: the bark is reddish on the young shoots, the buds are obtuse, the leaves are rounded at the base and less deeply lobed, and the teeth or waves of the leaf margins are barely noticeable. The leaves are less deeply lobed than those of any other plane and their verdure is the brightest, glossiest, and most beautiful. Since the nodes are spaced at closer intervals on the branches, producing more twigs and consequently more leaves, this tree combines the beauty of the plane with that of the lime, both trees having the same uses. This tree is more suitable than other planes for forming quincunxes, tall palissades, portiques, salles de verdure, and other garden ornaments.

Notes

1. The gardens of the Academy in the fourth century BC, situated outside Athens and enclosing Plato’s residence, were planted with planes (Thacker, 1979, p. 18).

2. Pliny the Elder’s description of the Tuscan villa, in Naturalis Historia, includes a reference to plane trees covered with ivy, which protected the riding ground and shaded the paths (quoted in ibid., p. 23).

3. Sir Francis Bacon (1561-1626), who was Lord Chancellor from 1618 and is celebrated for his essay Of Gardens, 1625, inherited the estate of Gorhambury in Hertfordshire in 1602. Gorhambury lies on the site of the Roman city Verulamium, which occupied a large area. Bacon was named baron of Verulam in 1618 and Viscount Saint Albans in 1620 or 1621 (Thacker, 1979, p. 131; Wacher, 1995, pp. 214-41; Encyclopedia Britannica, 1995, i.776-7).

4. That is, Louis XV.

5. The French Huguenot jewel merchant Jean Chardin (1643-1713) was chiefly responsible for making Persia known to Europe in the seventeenth century; his Voyages were widely translated. He spent a total of thirteen years in Persia when Isfahan was one of the biggest cities in the world. A keen observer, he was also indebted to père Raphaël du Mans’s L’Etat de la perse en 1660 for much of his information. Tehran was declared capital in 1789 by Agha Muhammed, the first Qajar shah of Iran (article ‘Chardin’, Peter France, in France, 1995, p. 152; Lockhart, 1989, p. 352; Stevens, 1979, p. 31).

6. These are the ‘bobbles’ of the plane tree (Mabey, 1996, p. 58).

7. The author uses the words ‘sur un filet commun’ (on a common filament). On the peduncle, see article Stalk.

8. A ‘volant’ is a large billhook atttached to a pole, which is used for pruning trees (Larousse, 1866-78, xv.1168).

9. Cf. article ‘Greffe’.

10. The wood of Platanus occidentalis or American plane, which is also known as American sycamore and buttonwood, is now used for pulp and furniture. See D. J. Mabberley, The Plant-book: a Portable Dictionary of the Vascular Plants (Cambridge, 1997), 565.

11. Platanus orientalis.

12. Platanus occidentalis.

13. Platanus orientalis variety insularis.

14. Platanus orientalis ‘Cuneata’ (Harris, pers. comm.).

15. This is Platanus + hispanica ‘Acerifolia’, the London plane.

16. Platanus occidentalis variety glabrata.