Agenda - Parks and Recreation Commission - 06/09/2005 - Joint with CC

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Willow Control Abatement of Bituminous Trail Surface Disruption by Willows Sandbar \Villoxvs (SalLY ex'igu~t) can be an extreme nuisance for bituminous surface managers in Minnesota where blacktop parking lots, roads and trails are in proximity to alluvial soils (former wetlands). These tree-like shrubs are very fast groxving and hardy - spreading most frequently through rhizomes (roots). These woody plants are prolific in generating nexv rhizomes, sending them laterally under or through the class .5 layer, where the push up vertically to form 'new' plants (actually clones). The shrubs have tremendous hydraulic capacig; and during the peak growing season, they can emerge completely through the pavement in a matter of days. Until they break through the blacktop, the surface may appear 'bm,npy' - and then the bumps break open from the upward pressure to reveal the green ft)liage and nexv stem material. ()ften these breaches in the pavement are only an aesthetic concern, with an edge of trail affected or only (,~e or more bumps in a single area. However, in locations where the willows are close to the trail and densely co~centrated, the frequency and the severity of their impact can create a trip hazard, especially for wheeled (e.g. in-line skaters) trail users. 'l. here are several methods of preventing, minimizing, and othenvise addressing the negative impact Sandbar \Villows (later referred to only as 'willows'), have on trail construction, maintenance, and the trail users. This d~)cument xvill provide a summary of the shrubs biology, and construction and maintenance issues associated with trails xvhere xvillows are present. Biology of Sandbar Willows There are several species of the willow family (Sa/icaceae), that naturally occur in central Minnesota. It should he noted that Sandbar Willows are the only significant plant that is a concern for Ramsey's mails. Occasionally, however, tree roots may push up moderate ridges in wooded locations. In addition, if living shrubs or tree stems are incorrectly buried during trail construction - these individual plants can sometimes cause the same damage that xvillows do, however, these are isolated instances, and remedies are apparent. Sandbar Willoxv identification The folloxving is from a US Army Corp of Engineers document: ISandbar ~villow is] an erect, deciduous shrub 2-5 m. lfigh. A distinctive characteristic of this willow is its long, linear leaves (usually 10 times longer than wide) that are irregularly toothed. Mature leaves are without hairs. Leaf stalks lack glands and no stipules are present. It often has many stems that are slender, reddish- brown, lack hairs, and are leafy. From 1-3 catkins (3-6(8) cm. long) emerge after the leaves. Fruit is a capsule that is hairless to thinly silky. In flower during May and June. 2iandhar willow is probably the most common willoxv in Minnesota ... frequently forming large dense, circular colonies that can be an acre or two in extent. [Eggers and Reed].