Planting Salt Resistant Vegetation

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A new resident of New Hampshire will soon recog­nize what road salt does to vehicles, but it is harder to seewhat it does to certain plants. Planting salt resistantvegetation along the roadside is essential since vigor isnecessary to survive in our sometimes intolerable weatherconditions. Hardy vegetation will save you from havingto replant the area if it dies because it is incompatiblewith its surroundings. Vegetative cover is necessary tocontrol erosion and protect water quality (by filteringrunoff). It is an important safety element since sedimentfrom runoff can cause blockage of culverts resulting infloodingand creating driving hazards.

How Road Salt Affects Vegetation

Since salt in soil absorbs water it can injury plants ifit accumulates to excessive amounts. Even if moisture isplentiful, high amounts of salt can result in a drought-likecondition because sodium results in compacted soil.Compacted soil doesn't allow the water and oxygen to getto roots ofthe plant.

Salt affects plants as it is absorbed through rootsand leaves or needles. As salt dissolves in water, sodiumand chloride ions separate, and chloride ions are absorbedby the plant roots. The ions are carried by the plant intogrowing sections and can accumulate to toxic levels.Toxic buildup results in marginal scorch (death of leafmargins). Plowing and vehicle traffic can spray salt onthe roadside. Where salt may enter plant cells directlythrough the leaves or needles affected plants lose theircold hardiness. Salt also reduces plant vigor, thereforethey become more susceptible to attack by insects anddiseases.

Symptoms of salt injury are similar to those causedby drought or root injury: stunted yellow foliage, prema­ture autumn leaf coloration, scorch, and twig die back.The conifer foliage often turns yellow or brown in theearly spring. If spray causes salt damage, discoloredneedlesare soon masked by new year's growth. If the saltdamage is caused by excesses in the soil, new needlesmay die as chloride ions accumulate in them. Either typeof damage could be lethal to a plant if it occurs for sev­eral consecutive years.

Common Sense Solutions

One obvious solution to curb salt damage is to sowsalt tolerant plants. To protect intolerant plants use saltspray barriers. Snowfencing or plastic shields also pre­vents spray to trees. Intolerant species shouldn't be

planted within 30 feet of roads or on slopes below road­beds.

After March 1, salt applications are most detrimen­tal because plants are breaking from their dormancy andare beginningto actively absorb nutrients and water fromthe soil. Toxic ions are more likely absorbed during thisperiod. Crews should avoid piling salt and snow aroundplants or in places where melting water will drain intothem.

Proper planting procedure is important. Newlyplanted trees are under stress and less able to cope withexternal factors (such as salt). The depression created bysettling of new transplants is an excellent place for saltywater from melting snow to accumulate. Depressionsshould be filled or leveled as soon as new transplants be­come established.

As mentioned earlier, soils containing large amountsof sodium frequently develop poor drainage. Treatingroadside soil with gypsum appears to be a successfulmethod of correcting the soils poor drainage. Also, onecan create adequate drainage systems for highways, curbsand gutters divert street runoff into storm sewers andclean ditches and culverts carry water away from raod­sides. Adequate drainage this will substantially reducesalt's effects on vegetation.

What to Plant

The University of New Hampshire's CooperationExtension program suggests planting salt tolerate treessuch as horsechestnut, black locust, honey locust, redoak, white oak. Moderately salt tolerant trees are ash,poplar, birches, cherry, and red cedar.

Permanent seeding of grasses and legumes shouldoccur before August 15. If this does not fit into yourschedule, annual rye grass is a quick temporary cover.Also, annual rye grass is a good choice in ditches that arecleared out yearly.

Permanent seeding should occur during April andMayor the first two weeks in August. The Maine De­partment of Transportation (MEDOT) suggests plantingcrown vetch and roseacaciait is non-invasive in forestcanopied areas, wetlands, and ditches. The MEDOTwarns that these species will invade croplands, pastures,lawns, and shrub beds.

Warm-season grasses are more useful for erosioncontrol than are cool-season grasses. Reliable warm­season grasses are switchgrass, little blue stem, big bluestem, indian grass, and prairie grass . Warm-season

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New Hampshire Road Scholars

We are pleased to recognize individuals who, during the Spring of1996, achieved thefollowing levels in the UNH f2 Center Road Scholar Program.

Road Scholar I. Participated in UNH T2 Centertraining activities which totaled 30 contact hours .

Master Road Scholar. Participated in UNH T2 Centertraining activities which totaled 100 contact hours andcovered the Road Scholar II range oftopics.

Road Scholar I AffiliationMaster Road Scholar Affiliation

Senior Road Scholar. Participated in UNH T2 Centertraining activities which totaled 70 contact hours andcovered the Road Scholar II range of topics.

Road Scholar II. Participated in UNH T2 Centertraining activities which totaled 50 ·contact hours andcovered a set ofminimum subject areas including roaddesign and construction basics, other technical, tortliability or safety, and supervision or personaldevelopment.

"Roadside Vegetation and Salt. " Deicing Salt and Our Environment, SaltInstitute. 700North Fairfax St. Fairfax Plaza. Suite 600; Alexandria VA22314-2040 (103) 549-4648

Quick Guides VegetativeErosion & Sediment Control No.3Hudler. George W. "Salt injury to Roadside Plants." New York State

College ofAgriculture and Life Sciences. Cornell University. Ithaca NYKelsey. Theodore "Gravel Pit and Other Sandy and Drought Site

Renovation Trials and Experiences in New Hampshire." Technicalnotes PM-NH-26May 1991 Soil Conservation Service. Durham NH

Walton. Clyde. "Using Sustainable vegetation management on MaineRoads." Better Roads. Vol. 64 n 7.•July 1994. p. 21-22.

grasses develop large root masses so it often appearsthat they are failing when instead all the growth isoccurring below the ground. The depth and strength oftheir root system are important. They germinate at aminimum solid temperature of 60 degrees so plant earlyin the season. Also, they grow the most during the heatof the summer (after May 15 in NH). Most warm­season grass will remain viable in the soil for severalyears and will not germinate until prolonged moisture isavailable. Because water flows through sand andgravel, the seedbed is usually too dry to allow the plantsto germinate . The most dependable method for seedingis to track using a bulldozer. The grouser tracks reduceerosion during the seedling establishment period

BristolHillsboroughHooksettLebanonHudsonEastman CommunityAmherstBrentwoodRaymondEidelweissMont VernonBartlettLyndeboroughSuttonSuttonNewmarket

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Mark BucklinJames CoffeyDennis Desrochers .Jay FitzgeraldMichael GospaderickRonald HansenDavid HerlihyDouglas IsabelleScott KeddyDavid MaudsleyJeremy PhilbrickL. Patrick RobertsAnthony RoccaDonald SharpDennis StevensDavid Walker

BerlinConcordNHDOTAltonMerrimack

Affiliation

WarnerGreenvilleTroyNew HamptonMiltonExeter

Affiliation

BridgewaterLempsterWashingtonLyndeboroughKingstonGilfordKingstonMerrimackClaremont

Ernest AllainE. Douglas BarnardKenneth FletcherKenneth RobertsJohn Starkey ,

Senior Road Scholar

Allan BrownCharles ButterickJames DiceyGordon HuckinsMichael SmithJohn Sowerby

Donald AtwoodPhillip HowardDavid HuntWalter KiblinGeorge MayhewRichard PetellRichard St. HilaireJoseph TomolonisKeith Weed

Road Scholar II

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