MORTON ARBORETUM BULLETIN POPULAR INFORMATION

Transcription

1 Vol. III No. 5 MORTON ARBORETUM JOY MORTON, Founder BULLETIN OF POPULAR INFORMATION By H. TEUSCHER, Botanist LISLE, ILLINOIS June 30, 1928 Subscription $1 a year, loc a copy. Copyrighted by Morton Arboretum TREES AND SHRUBS WITH COLORED FOLIAGE' Why are so many garden and plant lovers opposed to plants with colored foliage? If asked, they will most likely reply either: "Plants with colored foliage look so unnatural and out of place in the garden." Or, "Such plants only look sickly." These answers arouse the supposition that, in the first case, the varicolored forms which were displayed had not been placed skillfully and appropriately; and in the second, that varieties had been planted which were not worth having, There are, indeed, variegated forms which ar~ only of botanical interest and without any ornamental value. Their abnormal leaf coloring is caused by a lack of chlorophyll, the green substance in the leaves which enables the plants to assimilate inorganic matter with the help of the sun's rays. Such plants do not only look sickly but usually are more or less sickly. They do not deserve a place in our gardens. How should plants with colored foliage be grouped to attain pleasing effects? It will usually prove most satisfactory to group colored leaved plants by themselves and to display them either against tall conifers or against the house. Formal parts of the garden are generally better suited to show them to good effect than. informal parts. Most pleasing and most striking combinations are possible with perennial flowers of which a few examples may be given: 1. A hedge-like planting of Prunus cerasifera Pissartii Spaethiana (dark red), with a few tall stemmed Acer negundo variegatum (white and soft green) lifting their crowns at reg- 17

2 ular intervals just above the Prunus, will make a splendid background for a mixed perennial or annual border. Especially fine to display against such a background is a mixed planting of long spurred Aquilegia hybrids in all colors, or a colorful bed of Iris. 2. Sambucus racemosa plumosa aurea (bright golden yellow) as an informal hedge, without pruning, will make a striking background for dark lilac blue Iris in assorted varieties. 3. Malus purpurea aldenhamensis, pleasing in spring because of its beautiful semidouble, bright pink blossoms, will, if planted as a dense grove or an informal hedge-like row, make a beautiful combination with Ligustrum obtusifolium Vicaryi (bright golden yellow). The Ligustrums may be planted in a row against the Malus where they will serve also to hide the usually bare lower trunks of the Malus. Against the Ligustrum may again be displayed a border of bright blue Veronica spicata. How do plants with colored foliage originate? All species of plants are more or less inclined to vary in the character of their leaves, their growth, etc. This natural trend to vary usually increases under cultivation but varicolored foliage, especially red or yellow foliage, is just as likely to appear under natural conditions. The famous Purple Beech (Fagus sylvestris atropurpurea) and the Yellow Leaved Beech (Fagus sylvatica Zlatia), which were found wild in the woods of Europe, are examples of that. White variegated foliage usually appears as a so-called bud-variation on just one branch on an otherwise normal leaved tree. Through budding or grafting it is possible to raise from this one branch plants which have no other but variegated foliage. Bud-variation is most likely to appear. from so-called "sleeping buds" of the old wood which have been stirred into action by hard pruning or other disturbance of the tree. This fact gives us a valuable hint for the treatment of plants with varicolored leaves which frequently show a deplorable tendency to revert to the green type. Acer negundo variegatum, the famous white variegated form of the Box Elder, is a very good example of this peculiar phenomenon. Old plants of this variety usually get more and more green, but hard pruning in early spring will always restore them to their original beauty. LIST OF TREES AND SHRUBS WITH COLORED FOLIAGE TESTED AT THE MOR'J10N ARBORETUM In the following is given a concise enumeration and evaluation of an the trees and shrubs with colored foliage which, so far, have been tested at the Morton Arboretum. This list does not contain all the varieties which are in cultivation, but contains most of those which are really useful. The varieties which seem to be most worthy of consideration have been marked with an asterisk: 18

3 PICEA ORIENTALIS AUREO-SPICATA A spruce with fresh green young growth always is cheerful to look at, but there can be no more cheery looking plant than the form of the Oriental Spruce which is pictured above. Its old needles are dark green as are those of the type, but the young growth is bright golden yellow and shows off very conspicuously. Unfortunately this spruce is quite difficult to propagate and is of rather slow growth, so it will probably always remain a rare guest in our gardens. The plant which is shown on the above picture was imported by the Morton Arboretum from Europe. It seems that this variety is not yet in the American nursery trade.

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5 TREES AND SHRUBS WITH RED FOLIAGE Acer campestre Schwerinii. Brownish purple in spring, later dark green. Quite good. Acer cappadocicum rubrum. Young leaves and shoots blood red, getting green later. Good but somewhat tender. *Acer platancides rubrum (better known as A. pl. Reitenbachi). Young leaves greenish purplish, dark red' in summer. *Acer platanoides Schwedleri (the famous Schwedler-Maple). Leaves bright r ed when unfolding, later dark green. *Acer palmatum atropurpureum (the red leaved Japanese Maple). Pictured and described in our bulletin Number 6 of last year. *Acer palmatum ornatum. Cut leaved form of the above. Bright red. *Acer pseudoplatanus purpureum (also known as var. purpurascens). Under side of the leaves bright purple. It frequently leaves out green after transplanting but will show its typical coloring in the second year. *Berberis Thunbergii atropurpureum. The dark red form of the wellknown Thunberg's Barberry. Betula pendula purpurea. A dark red form of the European Birch. Very conspicuous and handsome; but the European Birch suffers so mu.::h from borers with us that its forms cannot be recommended for general use. Catalpa hybrida purpurea. Mentioned and described in our bulletin Number 6 of last year. *Corylus maxima purpurea. Mentioned before like the above. Fagus sylvatica atropurpurea, especially its form "Riversii", the Copper-Beech. Very conspicuous and: beautiful but with us rather difficult to establish and quite unreliable. Fagus sylvatica purjjureo-pendula. The drooping form of the above. '" Malus purpurea aldenhamensis. Best of the red leaved Crabapples. ''' Malus purpurea Eleyi. More tree-like, foliage just as red as that of the ~ bov e. Malus pumila Niedzwetzkyana. Foliage quite red, especially when young. ''' IJrunus cerasifera Pissartii Spaethiana. A dark red form which, unlike the commonly cultivated Prunus Pissartii, remains dark red all through the summer. Quercus robur atropurpurea. Dark purple, slow-growing form of the English Oak. *Quercus robur fastigiata purpurea. Growth upright like that of the Lombardy Poplar. Foliage dark red when young. *Rosa rubrifolia (R. ferruginea). Foliage bluish-purplish, very striking. Flowers rather small and not very conspicuous. TREES AND SHRUBS WITH YELLOW FOLIAGE Acer cappadocicum aureum (A. laetum aureum). Bright golden yellow with bronze tint, very good but unfortunately rather tender with us. Acer negundo auratum (usually known as A. negundo odessanum). Very handsome and the coloring quite permanent all through the summer, but more tender with us.. than all other forms of the Box Elder. *Acer pseudoplatanus Worleei. Deep yellow, petiole reddish. Getting more or less greenish later. *Acer saccharinum lutescens. Rather bright golden yellow when young, getting green later. Alnus incana aurea. Young leaves and branches yellow, catkins flesh pink, very pretty and conspicuous in spring but slow growing and somewhat tender. Cornus mas aurea. Rather bright yellow in spring, but somewhat fastidious and tender and of no importance for us. *Cornus alba Spaethii. Leaves with broad yellow margin. Quite useful and of very easy culture but reverts frequently to the green type. Evnnymus europaea chrysophylla. Yellow in spring. Without garden value. 19

6 Fagus sylvatica zlatia. Bright yellow in spring and very pretty but rather tender with us. Forsythia suspensa aurea. Yellow in spring. Without garden value. Fraxinus excelsior aurea (tota aurea). Branches and young leaves yellow. Quite pretty in spring. *Ligustrum obtusifolium (ibota) Vicaryi. Bright golden yellow. Of slow growth. Very good. * Ligustrum vulgare aureum. Faster and taller growing than the above but not quite so bright in color. Malus pumila paradisiaca foliis aureis. Without garden value. Philadelphus coronarius aureus. Quite pretty in spring but rather dirty yellow later in the season. *Physocarpus opulifolius luteus. Bright yellow when young, later bronze tinted. Quite good. *Populus canadensis aurea. Yellow only in spring. *Quercus robur concordia. Bright yellow, very conspicuous. *Sambucus racemosa plumosa aurea. One of the finest of all yellow leafed shrubs and in brightness of color as well as in general habit much superior to Sambucus nigra1 aurea and S. canadensis aurea. Sorbus aria chrysophylla. Deep yellow and very handsome but rather tender. *Sorbus aucuparia lutea (fr. Dirkenii). Bright yellow in spring, later more or less green. Syringa emodi aureo-variegata. Leaves with broad, greenish-yellow margin. Not very conspicuous. Tilia platyphyllos aurea. With bright yellow branches and soft yellow young leaves which later turn green. *Ulmus glabra lutescens. Leaves bright yellow, especially when young. *Ulmus procera Vanhouttei. Golden yellow when young, turning green later. TREES AND SHRUBS WITH WHITE VARIEGATED FOLIAGE *Acer negundo variegatum (argentei-variegatum). Probably the most useful of all trees with white-variegated foliage. *Acer platanoides variegatum (A. platanoides Drummondii). White and pinkish variegated. *Acer pseudoplatanus Leopoldii. White and pinkish variegated. Acer truncatum albo-variegatum. White and pinkish variegated. Very pretty but rather tender with us. Aesculus hippocastanum Memmingeri. Without any garden value. *Cornus alba argentei-marginata. Leaves with distinct white margin. Gives a grey effect from the distance. Cornus mas variegata. Leaves with white margin, difficult to establish and somewhat tender with us. Cotoneaster horizontalis variegata. Quite handsome and useful but unfortunately somewhat tender with us. *Crataegus oxyacantha Gireoudii. Young leaves white variegated. Young shoots red and very conspicuous. Fagus sylvatica tricolor. Leaves white, pink and green. More curious than pretty. Tender with us. *Fraxinus excelsior argenteo-variegata. Conspicuously variegated with white. Reminds one of the Box Elder. Fraxinus pennsylvanica aucubaefolia. Without garden value. Ligustrum obtusifolium variegatum. Spotted white. Of no account. Ligustrum vulgare glaucum (L. v. argenteo-marginatum). Leaves greyish green with small white margin. Not ornamental. *Prunus cerasifera variegata. Narrow leaves, white and pinkish variegated. Graceful. Of slow growth. Prunus cerasifera Pissartii Hessei. Narrow leaves, reddish with yellowish margin. Only curious. Quercus robur variegata (argentei-picta). Leaves with irregular white spots. Without garden yalue. 20