Re-Greening the Platte
by
Ken A. MacKenzie and Ben R. Urbonas
South Platte River Program

Over the last two years the South Platte River Program of the District has directed much energy towards work intended to return the vegetation along portions of the South Platte River to a more native condition.

Working with South Suburban Park and Recreation District, Colorado Water Conservation Board and the City of Littleton, we removed 365 Russian olive trees growing along the banks of the river south of Denver. This work was a continuation of an effort we began in 1997, which, to date, has removed over 1,000 Russian olives from the riverbanks. In areas where these exotic species were removed, there are now growths of native volunteer saplings, including Boxelders, Plains cottonwoods and Peach-Leaf willows. We have installed sleeves of wire fence material around many of these prized natives to help protect them from beaver damage.

In addition, working with Denver’s new South Platte River Park District, we have removed almost 300 dead or diseased Siberian elms along the river in the past two years. When removing trees, we leave behind some large sections of the cut tree trunk on the banks, lodged behind the stumps and trees left standing. Leaving these logs parallel to the river helps prevent soil erosion, creates habitat for wildlife, and provides a decaying biomass as habitat and as a nutrient source for new plant growth. Much of the remaining tree material was chipped and spread over the upper riverbanks as mulch. To replace the non-native Siberian elms, we have planted over 450 native Plains cottonwood and Peach-Leaf willow poles, about 8,000 sandbar willows, and over 3 million shrub seeds.

The District also continues to work with other groups to further the goals to revegetate the river. One of these was Fresh Start, a non-profit organization that provides Denver youth with a supervised opportunity to make court-ordered restitution for graffiti offenses. We dug holes and donated beaver protection materials for a tree planting effort by these youth. In addition, to give newly planted trees and shrubs a better survival opportunity, we donated a 195-gallon water tank and watering accessories to Fresh Start. They have used this truck-mounted system to deliver many thousands of gallons of water to new trees and shrubs in Denver. We also donated native shrubs and volunteered our personal time to assist with the planting efforts during Denver’s annual Trails Day volunteer event on the South Platte.

Returning native grasses, shrubs and trees to restored riverbanks and to areas overgrown with weeds and invasive trees and shrubs is a priority of the South Platte River Program. We pursue this goal with a four-pronged approach: (1) introduction of a mixture of native grass species appropriate for specific site conditions, (2) inclusion of native shrub seed into the grass mix whenever appropriate, (3) planting of native trees whenever site conditions permit and (4) use of rigorous weed control measures. In the past two years we have reseeded over 20 acres of restored riverbank and provided weed control mowing at least three times during the growing season at each of 27 project sites. This equates to 276 acres of weed-control mowing. We look forward to working with our partner communities, organizations and volunteer groups to return native plant species to the river banks.

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