Agenda - Parks and Recreation Commission - 04/11/1996

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Ex/sting trees thai significantly shade ~outh windows at midday d~-ing solar midwinter · (November to Januar~i) should be thinned (not . topped) if deciduous ~r removed if evergreen trees. The lower branches of tall trees within 15 feet of the south-side of a buildi~,g should be removed so midday, midwinter sub can shine below the branches. · Use Solar-Friendl~V Trees. To enhance solar gain during late winter, wh~lo still providing summer shade, use "solar-frieridly" trees to the southeast and southwest. For the upL~ta' midwest, the most solar-friendly trees ar~ deciduous species, setting · leaves in early May, I¢ and having sparse bm are fully hardy, the Ke butternut, and ash are trees. Moderately sola and red maple from nc isiag leaves ia late September, ches ia winter. Where they ~tuclcy coffeetree, walnut, Unong the more solar-friendly '-friendly trees include sugar rthem seed sources. Among the least solar-friendl~trees are evergreens and trees (such as some oaks) ~ retaia most of their leaves :. in winter. · · Shield Buildings .fi:om Winter Winds Plant Detrse Trees,Upwind. Plant shelterbelts on open rural sites and wi~di>reaks on moderate-sized lots to reduce winter ,a~ncls and reduce heating costs' Shelterbelts and windt~eaks should be to the west and north--the directic~n of the prevailing winter winds. Select trees tha! will retain their branches (and foliage) to the grc~und, are fairly stiff, and are' reasonably fast growing. This can include Norway and Colorado spruce, ~ouglas-fir, and for multi-row plantings, pine. Specie~ should be selected to optimize growth underlparticular site condition. On large, open sit~ where winter winds are strong, shelterbelts shotfld be planted more than 50 feet upwind of the stmimres they shelter and should' extend at least 50 feet ~uth and east of ~he s~ructures. Shelte'rbeltsiusually feature a shrub row (either upwind or dowdwind) to control drifting snow and up to seven rbws of trees (primarily / for a windbreak, the trees should ' Ix, spaced more closely together than a shelterbelt. Evergreens, such as spruce, can be spaced at 10 feet apart if the outsides of the row receive full sun. InCrease Neighb0rho0~ Tree Cover for Wind Reduction. The collective effect of buildings and trees measurably reduces wind from what it would be on a totally open site. The greater the number of trees in the neighborhoodl the greater the overall tree cover and the more effective the trees are in reducing wind. Public and private tree planting and preservation of existing trees should be undertaken to aid ia wind reduction and to reduce heating demand. Priority should be given to maximizing the number and height of trees wherever winter solar gain is not compromised. Neighborhood.shelterbelts should also be inco. rporated into development plans to the north and west of clusters of housing, particularly on unvegetatedsites. . .... Increase the Community-wide Urban Forest ..... " Preserve Existin~ Trees in and Near Urbarl Area~. The pavement and buildings of urban areas and the concentrated use of cars and machinery increase summer h~at in cities, creating "urban heat islands." Urban forests reduce summer heat island effects, so tree planting and preservation should be promoted throughout urban areas. Priority should be. given to maximizing the volume of tree foliage by preserving large healthy trees. Maximize Tree planting and Care. Healthy, actively transpiring trees provide the greatest benefit in moderating the heat island and directly sequestering carboh dioxide (as Well as other pollutants). Trees function most effectively and grow faster when they have sufficient water and urban stresses are minimized. Trees should be planted on sites most suitable for plant growth (parks, undeveloped lands, residential areas, office parks, etc.). Planting of highly urbanized sites like parking . evergreens). For long-term cost effectiveness, lots and downtown areas may also be necessary to shelterbelt evergreens s[hould be planted 20 feet apart ":3'.' provide community-wide climatic benefits. In such in staggered rows 20 fe~t apart. Deciduous trees should be spaced furthdr apart. Planted windbreak~ of only one or two rows of trees are appropriate wl~ere winds are less severe and adequate room is not a~ailable for a full shelterbelt. On an open, fairly windy site, a properly planted single row of dense evergreen trees can provide measurable wind reductions and energy savings of up to about 15%. Whet/only one row of trees is used cases, more attention is necessary to provide adequate water, soil aeration, drainage, tree protection, and maintenance. ' - Prepared by Peggy Sand, land,cape architect and consultant to the Minnesota Re.Leaf Program. . For a copy of the report Plantlngfor ~ntrgy Conxervation in t/w North and other publicatioas on energy conservation plantings, call the M.,ff)NR Inforra~i~ Center at (612) 296-6157 or toll fmc. 1-800-766.6000. 1993'~q