November 13, 1889.] 



Garden and Forest. 



543 



Autumn Colors of Foliage. 



THE brilliant autumn coloring of many of the trees and 

 shrubs in New England and the northern states and 

 Canada is very widely known and appreciated; and most Euro- 

 peans, who are so fortunate as to travel in this country at that 

 season, are filled with the desire to reproduce the same effects 

 at home. But the trees which are so gorgeous when the first 

 frost appears here are said to lose much of their native bright 

 autumn effect when transplanted to the gardens of Europe. 

 Various reasons have been advanced to accoimt for this pecu- 

 liarity, the most generally accepted being the fact that the cli- 

 mate of eastern JMorth America is much less humid than that 

 of Europe. This certainly appears to be an important point, 

 because the brightness of the coloring in a cool, wet season 

 like the present, when growth has continued until frost, is not 

 at all comparable with that of those years when the autumn is 

 dry and there is an abundance of sunshine. 



The early autumn frosts are usually considered an important 

 factor in the production of these crimson and scarlet effects, 

 but much more depends upon whether the season is cool or 

 warm, wet or dry ; and soil, situation, exposure, etc., also play 

 a part. 



Autumn changes in the color of the. leaves are said to be 

 due to the disintegration of the chlorophyll or green coloring 

 matter, and the presence of xanthophyll (yellow), and erythro- 

 phyll (red) and other coloring matter within the cells. 



Frequent studies and notices of the subject are to be found 

 in foreign works and journals. 



Among those most accessible and published in this country 

 may be mentioned the notice by Professor Goodale (l-'hysio- 

 logical Botany, p. 297), and a study of "The Autumnal 

 Changes in Maple Leaves," by W. K. Martin and S. B. 

 Thomas, in the Botanical Gazette for April, 1887. The follow- 

 ing statement from the latter (pp. 80, 81) is interesting and 

 comprehensive : 



"Chlorophyll, manufactured constantly under the influence 

 of light, is as constantly undergoing decomposition by the 

 metabolism of the cell. Under ordinary conditions, the manu- 

 facture of chlorophyll is sufficient to cover up its decomposi- 

 tion, and the leaf retains its green color. Under certain 

 changed conditions, however, such as intense light or dimin- 

 ished vitality, the decomposition of chlorophyll exceeds its 

 manufacture, and xanthophyll (probably one of the products 

 of decomposition) appears. In other words, xanthophyll is 

 being formed all the time, but only becomes apparent when 

 the manufacture of chlorophyll is checked. The condition of 

 intense sunlight gives us the occasional summer yellowness, 

 while to lowered vitality must be atti'ibuted the failure of 

 chlorophyll manufacture in the autumn. This lower vitality 

 is brought about by diminution of light, lowering of tempera- 

 ture, and probably causes in the plant itself. The common 

 notion that frost is the cause of autumnal coloration is true 

 only so far as it is one of the causes which tend to diminish 

 the vitality of the plant, and so the manufacture of chlorophyll. 

 Autumnal coloration may take ])lace before any frost. Xan- 

 thophyll then stains the chlorophyll masses yellow, which were 

 before stained green by chlorophyll. The red coloration is 

 brought about in a very different way, aserythrophyll is manu- 

 factured in the leaf, and stains the cell- sap, leaving the chlo- 

 rophyll masses untouched. This red coloring matter cannot 

 l>e discovered in any of the crude materials brought into the 

 plant, or in any other part of the leaves, except sometimes in 

 the phloem regions of the petioles. When the leaf falls and 

 the cell sap evaporates, and the chlorophyll bodies die, the 

 erythrophyll lays hold of the cell wall and solid contents and 

 stains them. In this way dried leaves retain their red color. 

 As erythrophyll is soluble in water, however, contact with 

 moisture will soon cause the most of it to disappear." 



An experiment, showing the effect of checking the growth 

 of a plant or a part of it, may be made by girdling young 

 branches of some of our trees or shrubs, which will cause the 

 foliage of the part above the girdle to change color while the 

 remainder of the plant is still green. It is interesting to note 

 the peculiarities of the autumn coloring of different individuals 

 of the same species, which often occur in Maples, Oaks, etc. 

 These individual characteristics usually remain constant year 

 after year ; and, as some of them are much more desiral:)le 

 than others, it would be an interesting point to prove that such 

 could be perpetuated by grafting as suggested in a former 

 number of Garden and Forest (vol. i., p. 410). It seems very 

 possible that varying results would be produced, according to 

 the kind of stocks used. Stocks of some of the foreign spe- 

 cies might produce quite a different effect in regard to autLmin 

 coloring than would be the case if the desired form was 

 grafted upon stocks of the same species. 



This is a field for some valuable experiments. If American 

 trees do not produce all their native splendorof autumn color- 

 ing when transplanted to Europe, it is also true that, as a rule, 

 few European trees develop much brilliancy when planted 

 here. But it is a well known fact that Japan can furnish many 

 trees and shrubs which, when planted in this country, are quite 

 as conspicuous in the autumn as some of our native species. 



There is no class of woody plants in this latitude which 

 contributes such rich autumnal effects in shrubberies or by 

 roadsides as those of the genus Rhus, better known as 

 Sumachs. The most striking one of them all (7?. venenata) is 

 also the most poisonous to nearly everybody, and but very few 

 handle it without some visible evil effects. 



The so-called Poison Ivy {R. Toxicodendron) also assumes 

 pleasing colors, and is valuable as a covering for stone walls, 

 etc. Its poisonous properties will always prevent it, as well as 

 the preceding species, from becoming a welcome plant in 

 much frequented gardens. 



But there are three native non-poisonous species, the Stag- 

 horn Sumach (7?. typhina), the Smooth Sumach {R. glabra) 

 and R. copallina, which meet all desires for the bright colors, 

 red, crimson, orange and yellow. The shining, polished look- 

 ing foliage of the last named species usually becomes of a 

 uniform rich purple. 



The Smooth Sumach is also frequently purplish at first, but 

 among the novelties at the Arnold Arboretum there is a form 

 of this species with foliage of an unvarying yellow color in 

 autumn. 



Japan also furnishes bright autumn foliaged species, the 

 best non-poisonous species yet introduced being Rhus semia- 

 lata, var. Osbeckii, which in favorable seasons assumes beau- 

 tiful orange and crimson tints. Another Japanese plant, Cer- 

 cidiphyllum Japonicuiii, belonging to the Magnolia family, 

 gives promise of rivaling all other trees in the beautiful tint- 

 ing of its leaves in favorable seasons or when planted on dry 

 ground. It is as yet, however, too rare and too little known to 

 be fairly judged. 



As the Sumachs lead the larger shrubs in regard to autumn 

 colors, so the Maples may be said to be at the head of the list 

 of trees. The Scarlet or Swamp Maple {Acer ritbrum) assumes 

 rich hues earlier in the season than any other tree ; and this is 

 followed, often before any frost, by the orange or gold, crim- 

 son or scarlet colors of the Rock or Sugar Maple. The small 

 Mountain Maple {A. spicatum) often assumes various rich 

 shades of red. The varieties of some Japanese species, nota- 

 bly those of A. polyinorphiim, which hardly become more 

 than shrubs here, are well known for their beautiful summer 

 foliage, which becomes intensified as autumn advances. 



There are few plants of the Pea family which become beau- 

 tiful on account of these rich colors as the life of the leaves is 

 withdrawn, but, among the exceptions, the Yellow-Wood {Cla- 

 drastis lutea) is very striking on account of the clear, 

 bright yellow color which it sometimes assimies in October. 

 The leaves of our Ash trees fall early, but before they drop to 

 the ground those of the White Ash {FraxiJtus Americana) turn 

 a rich brown or olive purple, or occasionally yellow. In its 

 best condition Sassafras officinale changes to a delicate buff 

 or orange color. 



The bright scarlets and crimsons of the Tupelo {Nyssa syl- 

 vatica) in autumn always call forth admiration, and, consider- 

 ing the graceful habit of the tree and its bright green leaves 

 in summer, it ought to be more frequently planted for 

 ornament. , 



The Scarlet Oak [Q. coccinea) is well known for the rich 

 scarlet which its leaves assume in late autumn ; and the 

 browns, reds, yellows and dark purples of individuals of other 

 species of Oak only make the Scarlet the more conspicuous. 



Although the Liquidambar is not considered very hardv in 

 the latitude of Boston, it is much valued further south and 

 west, and is cultivated in Europe for the deep crimson effects 

 of its autumn foliage. 



Many of the shrubs which assume rich autumn effects 

 become purplish, often a deep, dull purple, before the red and 

 orange colors show conspicuously. This is especially notice- 

 able in wet seasons and among plants of the Cornel and Heath 

 families. Cornus florida is an instance in which the early 

 effect is purplish, changing later to scarlet or crimson above 

 and russet beneath the leaves. Some of the other species of 

 Cornus undergo the same changes. Many of the \'acciniums, 

 Andromedas and Azaleas first become purplish, then crimson 

 and orange; and the foliage of a small, southern tree {Oxy- 

 dendrum arboreum) is at first intensely dark and at a distance 

 much resembles that of the Flowering Dogwood. The 

 Yellow-root {ZantJiorhiza apiifolia) is prizetl for its bright 

 orange colors of late autumn. 



