Garlic Mustard (Alliaria Petiolata)

Garlic Mustard (Alliaria Petiolata)

Mustard Family: Brassicaceae

Description: This introduced biennial plant is 1-3' tall. During the 1st year it consists of a small rosette of leaves, while during the 2nd year it becomes a little-branched plant about 1-3' tall. The leaves of 1st year plants are up to 2" long and across. They are cordate-orbicular with margins that are dentate or wavy and their upper surface has a reticulated network of veins. The petioles of these basal leaves are rather long and slender. The alternate leaves of 2nd year plants have a similar appearance, except that they are usually longer than wide, spanning up to 3" long and 2" across. The lower and middle leaves along the stems are usually cordate with either acute or blunt tips, while the upper leaves are often ovate. Both the stems and petioles of 2nd year plants are occasionally hairy, otherwise they are glabrous like the blades of the leaves. The foliage is often light green or yellowish green in appearance, otherwise it is medium green. The upper stems terminate in narrow racemes of white flowers. While in bloom, these flowers are bunched together toward the top of the raceme. However, as the flowers mature and develop seedpods, the raceme becomes more elongated and they become more separated.

Each flower is about ¼" across, consisting of 4 white petals, 4 light green sepals, a short cylindrical style, and several stamens with pale yellow anthers. The pedicels of flowers while they are in bloom are up to ¼" in length, although they become longer later. The blooming period occurs during late spring or early summer, lasting about 1-2 months. The flowers are replaced by narrow seedpods that are called "siliques." These seedpods are about 1½–2" long and narrowly cylindrical (although slightly 4-angled in circumference). Relative to erect stalk of the raceme, they are more or less ascending.As the seedpods become mature, the foliage dies down by the end of summer. Each mature seedpod contains a single row of black oblongoid seeds. The root system consists of a shallow taproot that is white and branches frequently. This plant often forms colonies by reseeding itself.

Range and Habitat: Garlic Mustard has been reported primarily in NE and central Illinois, where it is locally common. In other areas of the state, this plant is apparently less common or absent, however it is rapidly spreading. There is little doubt that it is more common than official records indicate. This plant was introduced into the United States from Eurasia. Habitats include moist to slightly dry deciduous woodlands, woodland borders, areas along woodland paths, semi-shaded areas in gardens and along fence rows, and partially shaded waste areas. This plant thrives in light shade or partial sun and it is intolerant of regular mowing. At the present time, Garlic Mustard is the worst herbaceous invader of deciduous woodlands in Illinois as it has the capacity to crowd out and destroy all of the native wildflowers that bloom during the spring. Effective measures of control include pulling the plants by their roots and spraying the foliage with herbicides. Cutting the flowering stalks from their stems is not an adequate method of control because Garlic Mustard is capable of regenerating new flowering stalks from lateral stems. Also, mature seeds can develop from any cut stalks of flowers and immature seedpods that are left on the ground.

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Silver Maple (Acer Sacharinum)

 Silver Maple (Acer Sacharinum)

Maple Family: Aceraceae

Description: This tree is 60-100' tall at maturity, forming a short broad trunk and an ovoid to obovoid crown that is defined by long ascending branches of considerable size. Trunk bark of mature trees is gray and rough-textured, consisting of flattened scales and straight to curving furrows. On very old trees, the bark may become slightly shaggy when the scales become curved and somewhat loose. Trunk bark of young trees and branch bark are light gray and more smooth, while twigs are reddish brown, smooth, and covered with scattered white lenticels. Pairs of opposite deciduous leaves occur along the twigs and smaller branches. Individual leaves are up to 6" long and 4" across; they are palmately divided into 5 primary lobes. The primary lobes themselves are often divided into shallow secondary lobes and their margins have a few large teeth. All of the lobes are sharply cleft and pointed at their tips; the primary lobes extend deeply into the interior of each leaf. The upper leaf surface is light to medium-light green and glabrous, while the lower surface is conspicuously whitened and glabrous to mostly glabrous (some hairs may occur along the undersides of the major veins). The slender petioles of the leaves are up to 5" long, light green to red, and glabrous.

Individual trees of Silver Maple can be monoecious or dioecious; trees with perfect florets are rare. Some trees are capable of changing their gender from year to year. Staminate florets occur in small dense clusters about 1/3" across on short lateral spur-twigs; these florets are nearly sessile and they vary in color from yellowish green to red. Individual staminate florets consist of 4 sepals, 4-6 stamens, and no petals. At the base of each staminate cluster, there are several scaly bractlets. Pistillate florets also occur in small dense clusters about 1/3" across on very short peduncles; these florets are nearly sessile and they vary in color from greenish yellow to red. Individual pistillate florets consist of 4 sepals, a pistil with a pair of styles, and no petals. At the base of each pistillate cluster, there are several scaly bractlets. The blooming period occurs from early to mid-spring before the leaves develop. The florets are cross-pollinated by the wind. Fertile female florets soon develop pairs of samaras (seeds with elongated wings). In each pair, the samaras are held about 90° apart from each other (or a little less) and they are joined together at the base. At maturity, individual samaras are 1½-2½" long, becoming light brown; they dangle from slender pedicels and fall to the ground during early summer. The root system produces woody lateral roots that are fairly shallow and widely spreading. The leaves usually become pale yellow during the fall.

Range and Habitat: In Illinois, Silver Maple is a common tree that is found in every county. Habitats consist primarily of moist floodplain woodlands, riverbanks, and swamps. In these types of habitats, Silver Maple is often one of the codominant trees. In drier locations, it is not competitive with Sugar Maple (Acer saccharum) and other trees in the long run because its seedlings are less tolerant of shade. This tree is often cultivated as a landscape plant in yards and parks. In urban and suburban areas, the offspring of these cultivated trees often escape into adjacent areas that are not mowed (e.g., fence rows and vacant lots).