# PRODUCTION OF MAPLE SIRUP AND SUGAR.

By A. HUGH BRYAN, Formerly Chief, Sugar Laboratory, Bureau of Chemistry, WILLIAM F. HUBBARD, Formerly Forest Assistant, Forest Service, and SIDNEY F. SHERWOOD, Chemist, Office of Sugar Plant Investigations, Bureau of Plant Industry.

## CONTENTS.

<table><thead><tr><th></th><th>Page.</th><th></th><th>Page.</th></tr></thead><tbody><tr><td>Sugar maples.</td><td>3</td><td>Maple sugar.</td><td>30</td></tr><tr><td>Sugar groves.</td><td>4</td><td>Care of apparatus.</td><td>32</td></tr><tr><td>Tapping the trees.</td><td>11</td><td>Yields.</td><td>33</td></tr><tr><td>Apparatus.</td><td>13</td><td>Marketing.</td><td>33</td></tr><tr><td>Maple sap.</td><td>24</td><td>Maple sugar and sirup production of the United States.</td><td>34</td></tr><tr><td>Maple sirup.</td><td>25</td><td></td><td></td></tr></tbody></table>

The production of maple sirup and maple sugar is purely an American industry, the United States and Canada being the only countries where these products are made.

The earliest explorers in this country found the Indians making sugar from the sap from maple trees, and in some sections, especially along the St. Lawrence River, producing it in quantity for trade. The crude methods of the Indians were soon improved upon by the white people, but beyond the tapping and boiling the general process is still the same as it was at that time.

For many years, especially among the early settlers of the northern part of the United States, and even in Kentucky and Virginia, maple sugar was the only sugar used. Some makers attempted to secure an article equal to the imported cane sugar, or muscovado, of the West Indies, with varying degrees of success. A few refineries for producing white sugar were operated with maple sugar as their raw supply. The iron kettle, birch-bark tank, wooden spiles, and old way of tapping yielded a dark, ill-tasting product, but with care and changes in methods and apparatus the products were improved.

## SUGAR MAPLES.

All maples have sweet sap, but from only a few species have sirup and sugar been produced in paying quantities. The sugar maple (*Acer saccharum*) and the black maple (*A. saccharum nigrum*) are practically the only trees used for this purpose, the quantities of sirup and sugar produced from the red maple (*A. rubrum*), the silver maple (*A. saccharinum*), the Oregon maple (*A. macrophyllum*), and the box elder (*A. negundo*) being so small that they are of no importance.

As a tree for the production of sirup and sugar in commercial quantities, the maple tree is confined in its range to the eastern and northern United States and the neighboring southeastern parts of Canada. Tables 3 to 6, inclusive (page 34), list the States in which maple sugar and sirup are produced and show the quantities made.

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Farmers' Bulletin 1366.

The sugar maple is a stately and vigorous forest tree, capable of growing in dense stands. It bears a plentiful crop of seeds, which in most places ripen in the early fall. These seeds germinate readily, and under favorable conditions the entire forest floor is heavily carpeted with seedlings, the foliage of which is eagerly eaten by stock. The young seedlings are very thrifty and can stand the shade of a complete forest cover. This tolerance of shade is one of the distinguishing features of the sugar maple, and, although it is less pronounced in later years, the mature tree has one of the most persistently heavy crowns in the forest.

In this bulletin, the sugar maple is not considered as a lumber tree, for which a long stem free of branches is desired, but rather as a paying producer of sap. This is a silvicultural problem radically different from that which ordinarily confronts the forester. The full and heavy crown with a large leaf surface must be developed in place of the long, clear stem. The sap flow must be continuous and plentiful. The best sap flow is where the change from winter to spring is slow, where the days are warm and sunny and the nights frosty. These conditions do not occur throughout the entire range of the species. A region where the ground thaws quickly and where the temperature does not vary greatly from day to night is not suitable for sap production. The "season" must be long enough, also, to insure sap in merchantable quantities. Such conditions are characteristic only in the Northern States, and as sugar making extends farther south it can be profitable only at altitudes which reproduce the climatic conditions of the North.

The black maple is generally considered superior to all others as a producer of sap. How far this is true is uncertain. In its general silvical characteristics it is similar to the sugar maple, save in the fact that it seems to prefer lower land, such as the banks of streams and rich alluvial river bottoms. It is found in Vermont, on the shores of Lake Champlain, and ranges southward, west of the Alleghenies, from Minnesota to Arkansas and eastern Kansas.

## SUGAR GROVES.

### GENERAL CONSIDERATIONS.

The quantity of sap that a tree yields stands in direct relation to the size of its crown. Many sugar makers, however, believe that trees in a forest produce more sap than those in a grove. The explanation is found in the fact that the forest floor with its covering of litter and humus contributes to the vitality of the trees more than the grass carpet of a grove. To obtain a heavy sap production a complete crown cover and a rich deposit of humus are of vital importance in the management of a sugar grove (fig. 1).

The model grove should satisfy the following requirements as far as possible:

* It should contain the greatest number of trees per acre consistent with fully developed crowns.

* The forest cover should be unbroken, so that in summer little sunlight falls upon the ground.

* There should be a complete litter of humus and leaves, to the exclusion of grass and light-demanding weeds.

* Young trees should be kept in reserve to take the place of those that fail, and to fill other openings in the cover.

Production of Maple Sirup and Sugar.

5

No grazing should be allowed in the grove, except in special cases where the cover is perfect and no reproduction is needed. Cattle not only keep back all reproduction, but also do harm by trampling and breaking the ground, so that it dries out.

The grove should be made accessible by a system of roadways to facilitate the collecting of sap. If the network is complete no difficulty will be found with the underbrush, which hinders sap gathering little in the early spring when the woods are devoid of foliage.

FIG. 1.—A sugar maple grove of old forest-grown trees. The large crowns of the trees and the shady forest floor, covered with litter and humus, help the flow of sap.

IMPROVING A DENSE MATURE GROVE.

Many groves are merely parts of an old hardwood forest, having a large number of sugar maples in the mixture. These trees have their normal forest form—a long, smooth stem and compact crown. There is little to be gained in actual sap production by thinning such a stand, as it has generally passed the period of vigorous growth and would not develop larger crowns, although the sap season may be brought on earlier by opening up the grove to the sunshine. The mixture can be regulated, however, and provision made for a pure growth of maple to succeed the old forest as it passes away. The usual mixture of birch, beech, elm, basswood, and ash may be gradually removed and the reproduction of maple thereby assured. This thinning should pay for itself in most localities from the resulting fuel and saw timber. In making such a thinning the following precautions should be observed:

When the trees to be removed are in groups, all should not be cut out immediately, leaving large gaps in the forest cover, since forest-grown sugar maples have a broad, shallow root system, and are subject to windfall when suddenly exposed. The trees which crowd the best maples should be taken out first; the rest should be removed later, when the sugar trees have become more wind firm.

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Farmers' Bulletin 1366.

Where several maples crowd one another and form a dense cover, those with the smallest crowns, those which are unsound, and those which show signs of bad health or decline should be removed.

Young maples which show possibilities of good crown development should be freed from interference on every side.

If the grove borders on open land, it should not be thinned for a distance of at least 25 feet from its edge. This is a safeguard against damage by storms and is particularly important in borders exposed to heavy winds.

When practicable, the young growth of species other than maple should be removed.

It is well to accomplish the thinning in a series of years, rather than at once and radically, thus avoiding violent changes.

It is important to maintain the humus and ground moisture in every maple grove. Where natural forests of sugar maple are common the danger of destroying the proper soil conditions by letting in the sunlight is not great, but if a grove of this type lies where the summers are hot the cover must be broken very gradually.

## IMPROVING AN OPEN MATURE GROVE.

In the more settled and less wooded portions of the maple sugar producing district a large proportion of the groves are old and very often overmature. They have evidently been left on favorable situations from the original forest, and as a rule no attempt has been made to renew them or keep up their vigor since the adjoining land was first cleared. Among the great number of old, open, and grass-grown groves, a young and thrifty set of trees is rare.

As a rule, these groves are on small farms, where they are used as much for pasture as for sugar making. Where the pasturage can not be spared and where sugar is only a small item in the farm production, there is little to be done for their improvement. When the grazing can be spared, however, and the owner desires to increase the sugar-producing capacity of his trees, it is better to bring about a reproduction from the old trees than to plant a new stand.

In an open and grass-grown grove the first step is to exclude stock. After laying out driveways for sap gathering, the seedlings should be allowed to come up everywhere else. All unsound and dying trees should be cut out and young growth of all species other than maple removed. In a very short time the young maple seedlings will take possession of the open ground and grow vigorously where they get enough light.

When they are 8 or 10 years old and 6 to 8 feet high, or more, the struggle for supremacy among them begins. In each opening large enough to permit the development of a tree with a full crown, the strongest and most thrifty seedling which has a favorable position should be selected, and the heads of those within a radius of 12 feet or more about it should be lopped off with a corn knife. The crowns of at least two-thirds of these trees must be removed; the remaining crowns will insure a good ground protection and leaf fall until the favored tree has filled the opening. In small openings the thicket should remain unthinned. The struggle between the trees will keep them all suppressed, and they will supply the necessary ground cover. The seedlings which come up under the direct shade of the old trees will never grow to any size, unless some of the large trees are removed by age or accident.

to Mary Runtle
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7

Cattle may be let in the grove when it has become too tangled for convenient sap collecting and when the young growth desired for open places has reached a height of 8 or 10 feet. They will soon open up the smaller and undesirable growth. At the same time roadways should be opened and the ground kept free of fallen limbs and trees. The tall, slender seedlings will be a small obstruction in sap gathering, but a little discomfort can be borne for the sake of the undoubted advantages obtained by a ground cover.

IMPROVING A DENSE YOUNG GROVE.

In many parts of the maple-producing section a second-growth forest similar in composition to the original stand has come up. When, as often happens, the sugar maple forms the greater part of such a wood, all that is needed to turn it into a sugar grove is to remove a number of interfering trees, thus giving the proper number of maples a chance to develop the full crowns necessary to a maximum yield of sap per acre. Preference should be given to the younger and more thrifty stands, where the trees are just entering the period of most vigorous development.

In thinning a young stand provision must be made for growing a set of full-crowned sugar trees from the more thrifty of the young maples. In a stand from 40 to 60 years old it is easy to pick the largest and best-developed specimens and favor them for the future. Some of the directions for treating a dense young grove are the same as those for treating the mature grove.

Select the sound, dominant trees which show a natural tendency to a well-branched, compact crown of large size, and remove from all sides everything which tends to crowd them. If the stand is between 40 and 60 years old, leave about 100 trees to the acre; if older, leave about 75 trees. The average healthy young maple can be freed for 10 to 12 feet on all sides of its crown without the slightest danger, except in the most exposed positions.

In the choice of sugar trees the position and influence of each on its neighbors must be considered. If two dominant trees crowd each other seriously, remove the less promising one.

In case the beech, birch, or other species are so grouped that their removal would make a serious gap in the forest, it will be well to let several of them stand. They should be so treated, however, that maple seedlings, which nearly always gain possession of the soil, even under beech, will have light enough to come in under them. When these seedlings become established the beech or birch can be removed and young maples favored. When practicable, always cut out seedlings other than maple.

Successive thinnings are better than a radical opening up of the stand, because in this way danger of windfall and drying out of the soil are avoided. This method also leaves room to overcome the damage done by porcupines, which probably are the worst enemies of the young maple. One porcupine in a single night can strip the bark off many saplings, and to such an extent that they are permanently ruined. The sugar trees should not have more than 10 or 12 feet of free space on any side of their crowns. A thrifty maple can fill such a gap in eight or ten years, after which a final thinning may be made and the remaining weed trees removed.

The edges of the grove which border upon open land should not be thinned enough to leave the stand unprotected from strong winds

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Farmers' Bulletin 1366.

and sunlight. If other species are crowding the dominant maples, they should be removed. As a rule, however, the borders should remain dense and the trees should be covered to the ground with foliage.

In cool or elevated regions, the thinning may be more extensive than farther south or in lower lands, where more care is necessary to preserve a proper ground cover. Firewood and other timber secured by thinning should pay for the cost of the operation. The necessity for well-placed roadways to take out the sap should not be forgotten.

MANAGEMENT OF A SAPLING THICKET.

Throughout the maple region dense thickets of young saplings are common in abandoned fields and pastures. Where a sugar grove is desired, it will pay to take such young growth in hand if old trees are not available in sufficient numbers. Left to themselves, the

FIG. 2.—Stand of maple seedlings in need of thinning. Many suppressed and undesirable trees take up the food and light needed for the growth of the better trees.

young trees usually become so densely crowded that even when 20 feet high they number from 2,000 to 3,000 to the acre. Under such conditions growth almost ceases, even in the dominant trees, and at a time which in normal stands is the period of most vigorous growth.

The first thinning should be made when the saplings are about 6 or 8 feet high, if the owner feels justified in helping them at this time. The largest and healthiest trees, on an average about 12 feet apart, should be selected, and the tops of the others cut back with a hatchet or a corn knife in such a way that they can not overtake the favored individuals.

Cutting back trees in this manner can be done very rapidly. Three men should cut over an acre a day. Although there is no return in

AFTER 5 DAYS RETURN TO

# AUTOS

## Farewell to Soybeans

In 1929, Henry Ford I discovered the soybean. Soon he was passionately convinced that it would work brave new industrial miracles. Before long, dumfounded visitors at Ford's drank soybean milk, ate soybean butter spread on soybean bread, came away convinced that old Henry would soon be turning out a soybean auto.

He pretty nearly did. He made soybean gearshift nobs, horn buttons, accelerator pedals—and even experimental bodies. But if soybean plastics were strong, they were also expensive; cheaper plastics were just as good or better. So last week young Henry Ford II pruned out the last of the soybean projects. Having converted two soybean-processing divisions to other work, Ford's sold a third plant, at Saline, Mich., to Soybrands, Inc. The selling price was secret, but it was no secret that the soybean era at Ford's had ended.

TIME, NOVEMBER 4, 1946

WASHINGTON, D.C.
NOV 19 1946
7:30PM

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