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Posts tagged “Ulmus americana

Elm Cockscomb Gall

Galls, abnormal plant growths caused by a variety of agents including insects, come in myriad sizes, shapes and colors.  One of the most distinct is the Elm Cockscomb Gall which is caused by an aphid (Colopha compressa).  These galls, named for their striking resemblance to a rooster’s comb, are maturing and turning red this time of year. 

For much of the summer the aphids responsible for these galls live underground sucking sap from grass roots.  In the fall a new (sexual) generation is born, takes to the air, mates and heads for an American Elm (Ulmus americana) tree where each female aphid lays a single egg under the bark.  In the spring the emerging nymphs seek young American Elm leaves on which to feed.  As they do so, the aphid nymphs emit compounds that result in the formation of galls.  Each nymph matures inside a gall and then reproduces asexually, giving birth to hundreds of young within the gall.  The mature, reproductive adult aphid dies and the young aphids develop into winged adults that exit the cockscomb gall through a slit on the undersurface of the leaf.  These aphids then go down into the soil to feed on the sap of roots until the next generation is born.

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Elm Seeds Important Early Source of Food For Wildlife

elm seeds 0U1A0175Tips of American Elm (Ulmus Americana) branches dropping on the ground alerted me to the fact that something was going on in the crown of the elm tree above me. Sure enough, a Gray Squirrel was busy dropping branch tips after harvesting the elm seeds on them. Because their seeds develop long before most seeds are available, elm seeds are sought after by numerous song birds, game birds and squirrels. This was verified by the presence of the Gray Squirrel, as well as a Rose-breasted Grosbeak and an Indigo Bunting (see photo), both of which took intermittent breaks to sing, but spent most of their time consuming elm seeds.

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Bud Scales

bud scales 147Much of this coming summer’s woody plant growth is contained in embryonic form inside a tree’s buds. Buds contain an undeveloped shoot, leaf, and/or flower. Formed last summer, these buds must survive the freezing and fluctuating temperatures, relatively dry air and the potential insect, bird and fungal damage that may occur during the fall, winter and early spring.

Bud scales, which are small, modified leaves, cover and protect many of these buds. The number of scales, their arrangement, color, presence or absence of hairs or sticky substances are often distinctive. Willows have one visible bud scale (actually two fused into one), whereas pine and fir buds may have anywhere from 100 to 350. The scales on a bud can either be arranged in pairs facing each other edgewise (American Basswood, pictured) or overlapping like shingles (Sugar Maple, pictured). Colors range from the wine-colored bud scales of Striped Maple to the mustard yellow Bitternut Hickory scales. The texture of bud scales has great variation, including the satiny-smooth hairy bud scales of Box Elder (pictured). Many bud scales, such as poplars, are covered by a gummy substance which serves as added protection.

A few trees and shrubs have buds that lack scales. These are referred to as “naked” buds, and often the embryonic leaves are quite hairy. Witch Hazel, Hobblebush and Staghorn Sumac (pictured) are species of woody plants lacking bud scales.

Most buds have multiple scales which, upon falling off when the bud opens, leave a series of horizontally-elongated scars on the surface of the growing stem. By means of these scars one can determine the age of a young branch, since each year’s growth ends in the formation of a terminal bud which produces an additional group of bud scale scars. Continued growth of the branch causes these scars to be indistinguishable after a few years so that the age of older branches cannot be determined by this means.

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