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Winter Salt Injury and Salt-Tolerant Landscape Plants

Winter Salt Injury and Salt-Tolerant Landscape Plants

A3877

Winter salt injury and salt-tolerant landscape

Laura G. Jull

inter in Wisconsin often means snow and ice.To allow safe travel for pedes- trians and motorists, walkways and roads SoilTypes damage. ofWhen salt salt accumulates damagePlant can take up salt, leading to mustW be kept as ice-free as possible.While in the , excessive sodium (Na) from salt accumulation in the . Plants may also snow and ice removal is best done with destroys soil structure, raises soil pH, and have salt deposits on surfaces, such as shovels, snow blowers, and plows, this may reduces water infiltration and soil aeration, twigs, , or , causing tissue dehy- not remove all of the snow, and ice can leading to soil compaction, increased dration. Build-up of deicing salts in the quickly form, leaving , hazardous erosion, and water runoff.The soil becomes plant can interfere with photosynthesis surfaces. Deicing salts are used extensively unsuitable for proper growth and and other plant processes, like respiration to melt this ice and snow. plant development. Deicing salts are also and transpiration. Chloride (Cl) ions in salt Sodium chloride (NaCl), or rock salt, is the detrimental to beneficial mycorrhizal fungi can injure plant tissue, reduce water most commonly used deicer due to its in the soil, which form a symbiotic relation- uptake, and cause nutrient imbalances effectiveness, availability, and compara- ship with roots assisting with nutrient such as magnesium (Mg) and potassium tively low cost. However, it also has signifi- uptake. (K) within a plant. Salt applications made in late winter or early spring cause the most cant drawbacks. It’s highly corrosive, Plant damage. Salt is moved off the damage compared to applications made causing significant environmental damage pavement and into the environment by earlier due to active uptake of water by the and corroding vehicles and concrete.The one of two mechanisms: it may accumulate root systems as plants are beginning to national cost of damage to vehicles and in the soil along streets or sidewalks from break their . In areas where salt infrastructure alone is estimated at $3.5 to melted, salt-laden snow or it may become concentrations are high, native vegetation $7.0 billion annually. dispersed in an aerosol spray by fast- is being replaced by salt-tolerant, invasive This publication focuses on recognizing moving traffic and high winds along wet, species such as reed canarygrass and preventing plant damage caused by salted roads.This dispersed salt causes sig- (Phragmites australis) and/or narrow-leaved deicing salts, evaluates the pros and cons nificant damage to turfgrass as well as cattail (Typha angustifolia) leading to land- of alternatives to rock salt, and provides an landscape and wetland plants growing scapes dominated by a single species. extensive list of salt-tolerant plants. near or along roadways, highways, drive- ways, and sidewalks. People. Well water contaminated with While salt runoff is excessive chloride contributes to hyperten- typically limited to sion and other heart related conditions in areas bordering humans.The intake of high chloride levels salted roadways, salt from salt may also be associated with spray can travel elevated mortality from cancer. Maximum hundreds and even safe level of chloride in drinking water is thousands of feet 250 mg/L (250 ppm) but salt runoff often from the road. exceeds these levels. Water quality. Water quality can be adversely affected by road salt runoff into lakes, ponds, rivers, and wetlands. Wildlife. Local wildlife lose food and shelter as plants die due to excess salt. Browning along the edges of these leaves may be indicative of salt injury.

— 1—  winter salt injury and salt-tolerant landscape plants Indications of soil salt injury I Most damage occurs within 30 feet of Diagnosing road and decreases with distances from Symptoms of Diagnosing salt injury can be difficult road Salt spray becausesalt similar injury symptoms may result from salt injury I Plants are severely injured in poorly Salt spray enters plants through buds, a wide variety of causes.The following drained or where runoff from salt- and scars, young shoots, as well as the problems all cause similar symptoms: laden snow collects leaves of species. Salt drought stress, root damage from con- deposited on plants draws moisture out of struction, girdling roots, winter burn of I Damage increases with amount of salt the tissues causing desiccation (drying) foliage, air pollution, compacted soil, grade used and burn. Recent research indicates that changes, nutrient deficiencies, insects and I Plants growing near areas that receive salt spray injury contributes to winter diseases, natural gas leaks, water-logged frequent salt applications (walkways, injury, although it does not normally affect soils, and improper planting depth.There parking lots, entrances) show most cold hardiness of dormant buds on woody are, however, some details to look for that damage ornamentals.The morphology and physiol- may help: I Plants damaged over several years lack ogy of a plant bud appear to work vigor and are in decline Indications of salt together determining tissue sensitivity to spray injury If salt injury is suspected, either foliar deicing salts and freezing temperatures. I Salt damage more severe on side of analysis or soil salt tests are needed to For example, species that have naked buds plant facing the road or on outer confirm the diagnosis.These tests are avail- (no scales on buds) appear more suscepti- portions of dense plants able at a soil and plant analysis lab for a ble to freezing and to deicing salt than nominal fee. Collect soil samples in early species with multi-scaled (covered) buds. I Severity of damage increases with Buds are most susceptible in late winter volume and speed of traffic and amount spring before rain leaches salts out of the and early spring as they break dormancy. of salt used sampling area. Leaf and stem tissue samples can be submitted during the The degree of bud injury can be influ- I Plants downwind from road show more growing season for chloride content. Foliar enced by the plant’s genetic differences, damage than upwind chloride concentrations that exceed 0.5% type of salt exposure (aerial spray or soil I Most damage occurs within 60 feet of dry weight for and 1.0% for decid- salt), intensity of the salt exposure, biotic road and decreases with distance from uous plants are considered harmful. Use factors, climate, and seasonal differences. road clean pruners and wear gloves when

I Sensitive plants show symptoms of salt handling the samples to avoid contamina- damage at distances as much as 1,000 tion of sample, or prune the tissue directly feet or more from major highways into plastic bags. Contact your county Extension office for specific instructions, I Branches covered by snow or sheltered location, and costs for this service. from road show no damage

I Branches growing above spray drift zone show no damage

I Plants that are less cold hardy show more injury

Salt accumulation and damage of Japanese pachysandra foliage

— 2— Symptoms on Soil salt Symptoms on plants Unlike salt spray injury, soil salt injury is deciduous plants I Injury appears in early spring slow to develop and injury progresses over I Browning along edges of leaves

I Delayed budbreak several years. Deicing salts create a wide I Wilting during hot, dry weather when range of problems for plants. Salt is highly soil moisture is limited I Reduced leaf size and stem growth absorbent and binds tightly with water, I Off-colored or discolored foliage I Off-colored foliage preventing plant roots from taking up I Nutrient deficiencies, in particular mag- I Outer edges of leaves turn brown water.Thus, even when soil moisture is nesium and potassium I Plants may fail to plentiful, high salt levels create an artificial, drought-like environment for plants. I Stunting and reduced plant vigor I Death of buds and twigs leading to mis- Compounding the problem, high concen- shapen, unsightly looking plants I Plant produces fewer, smaller leaves trations of soil salt can actually draw water that are often chlorotic (yellow) I When the tip of a branch dies back, out of the roots.When roots do absorb salt, I Premature fall coloration and leaf drop many new shoots sprout just below the high concentrations will eventually kill dead area, creating a ”witches’ broom" roots, causing plants to decline over I and smaller than normal

I Crown of the begins to thin several years. At high concentrations in the I Twig dieback soil, sodium (Na) will compete with essen- I Large branches may die if severe injury I Turfgrass and herbaceous perennials tial nutrients for uptake by plants. Roots occurs over several years may die due to excessive soil salt will also absorb toxic levels of chloride (Cl) Symptoms on evergreens from deicing salts, which accumulates in Symptoms on evergreens I Injury evident in late winter to early buds, leaves and twigs, causing desiccation I Similar to salt spray injury, but both old spring (drying). Since an affected plant’s health is and new needles are affected compromised, it become more susceptible I Tips of mature needles turn brown or I Eventual plant death to insects, diseases, and drought stress. yellow; discoloration moves down the With regard to soil texture, plants tend to needle, eventually killing entire needle; be more salt tolerant in sandy, well-drained damaged needles eventually fall off soils than in heavy clay soils as the salt is I Discoloration of needles is often hidden more easily leached through the soil by by new growth in spring rainwater.

I Twigs die back

I Symptoms occur primarily on the side of the plant facing the road

the tips of these eastern white needles are turning brown from salt injury. Damage will progress inward, eventually killing the needles.

eastern white pine damaged on side of tree facing the road. Note salt damage did not occur on lower foliage due to snow cover.

— 3—  winter salt injury and salt-tolerant landscape plants Prevention Prevention tips I In early spring, water soil heavily (at of salt injury I One of the best preventive techniques least 6 inches) to flush salt out of the There are many ways to prevent or allevi- is to plant salt-tolerant species in areas plant’s root zone. ate salt injury. Deicing salt applications that are subject to salt spray or runoff I Direct salt runoff away from plants should be used primarily in high-risk areas (see table 1). Be aware that a plant’s using barriers such as gutters or alter such as highways, intersections, hills, steps, degree of tolerance to soil salts may be drainage patterns away from planting and major walkways; limit applications in different from its aerial salt tolerance. areas. (This method works best on well- non-critical areas. If possible, avoid using I In areas where soil salt is a problem, drained soils and is not very effective on pure sodium chloride (NaCl), a common planting trees and on berms clay soils and compacted soils where deicing salt. Instead, mix less than 5% of (raised, mounded beds) will prevent water does not drain readily.) sodium chloride (NaCl) with mate- salty runoff water from moving into I Application of (CaSO ) to rials such as sand, crushed rock, kitty litter, 4 root zones. heavy clay soils that are high in salt will ash or cinders, or use an alternate deicing displace the sodium ion with calcium, product (see table 2 for a comparison of I Protect plants from salt spray by placing improving both aeration and drainage. available products).These mixtures are physical barriers such as plastic, burlap, particularly useful on roads with low traffic or snow fencing around or near plants I If salt-sensitive plants are to be used, volume and when temperatures fall below in late fall. plant them at least 60–100 feet from

20°F (sodium chloride is ineffective at I Avoid shoveling salt-laden snow over highways and 30–40 feet from city colder temperatures). For example, 1 the root zones of sensitive plants. streets where salt runoff into soil is pound of deicing salt mixed with 50 common. I During a warm spell in winter, rinse off pounds of sand makes an effective plants to eliminate residual salt before Use of anti-transpirants and dormant oil abrasive compound, particularly on budbreak. sprays are ineffective in prevention of salt walkways where good foot traction is spray injury and are not recommended. required.This combination stays loose and unfrozen and is easy to spread; however, there is usually not enough salt to do any appreciable melting. Do not use commer- cial fertilizers as a deicing salt as these products will burn plant roots. If using a deicer, wait to apply until after all the snow has been plowed or shoveled. Early applications of small amounts of salt can be very effective in keeping ice from bonding to the pavement, which improves removal of snow and ice after a storm. Remove slush before it has a chance to refreeze. Once ice has bonded to the pavement, it takes more salt to remove the ice than if a lighter application been made earlier. If possible, avoid application of salt in late winter and early spring as the plants are coming out of dormancy.

On deciduous trees, clusters of new shoots, known as “witches’ brooms,” sprout where branch tips die back.

— 4— Products Why some plants are salt tolerant for ice control and alternatives A variety of physiological characteristics are involved in making There are several chemicals commonly plants tolerant or susceptible to salt. used as deicers.They are often blended together or combined with other materials such as sand, cinders, ash, agricultural Protection against salt spray. Some plants have byproducts, or other proprietary material features that physically prevent salt spray from penetrating. Such to improve performance, limit environ- mental and concrete damage, and reduce features include hidden or submerged buds; thick surface ; cost.There are many commercial blends numerous, tightly arranged bud scales; fuzzy buds; or sticky resin- available in local stores with different per- centages of deicing chemicals. Some coated buds. (None of these structures protect the plant against deicing compounds are sold with anti-cor- soil-borne salt, which is taken up through the roots.) In contrast, rosive additives.While additives help, they will not eliminate corrosion entirely and plants that produce naked buds (no bud scales) are very suscepti- their effects on plants and the environ- ble to salt spray injury in winter, more so than plants with scaled ment are often unknown. buds. Examples of plants that have naked buds include wayfar- Performance of a deicing product is influ- enced by many factors including chemical ingtree (Viburnum lantana), Koreanspice viburnum concentration, air and pavement tempera- (Viburnum carlesii), Judd viburnum (Viburnum x juddii), pawpaw tures, traffic and weather conditions, type of road surface, topography, traffic volume, (Asimina triloba), witchhazels (Hamamelis spp.), fothergillas width of application, duration of the (Fothergilla spp.), and the highly invasive tallhedge buckthorn deicing salt melting action, shape of the deicer particles, and the time it takes the (Rhamnus frangula ‘Columnaris’). deicing salt to form a brine. Consider a balance between safety, cost, and practical Protection against soil salt. Some plants, such as storage and application issues when green ash (Fraxinus pennsylvanica), are able to exclude soil salt selecting a final product to use. Always follow label directions when using from entering their cells or they may be able to withstand higher a deicing product. Never over-apply concentrations within the cells. deicing products as this may cause serious damage to plants and the environment. Varying degrees of tolerance. An individual plant’s tolerance to salt will vary depending on its state of dormancy, on temperature fluctuations, and on morphological changes. Plants exhibit the greatest resistance to salt damage in early winter (December through early January). In March and April as spring approaches, buds become much more susceptible to salt injury. Newly planted trees and shrubs, which have small root systems and little stored water, are more susceptible to salt injury in winter than established plants. For these plants, extra attention should be given to preventive measures during the first few years after planting to help protect plants from salt damage. 

— 5— Ta b l e 1 . Salt-tolerant landscape plants

Deciduous trees Deciduous trees s p r a y s o i l z o n e s p r a y s o i l z o n e

H Acer campestre Hedge maple 5b MMQuercus ellipsoidalis Northern pin 4a

H Acer miyabei Miyabe maple 4a M Quercus imbricaria Shingle oak 4b

H Acer platanoides maple 4b MMQuercus macrocarpa Bur oak 3a

H Acer pseudoplatanus Sycamore maple 5b M Quercus robur English oak 5a

M Acer tataricum subsp. ginnala Amur maple 3a MMQuercus rubra Northern red oak 3b

H Aesculus x carnea Red horsechestnut 5a H Robinia pseudoacacia Twisty Baby® black locust 4b ‘Lace Lady’ (fruitless) HMAesculus hippocastanum Common horsechestnut 4b H Salix matsudana ‘Tortuosa’ Curly , 4b M Amelanchier x grandiflora serviceberry 3a contorted willow

M Betula nigra River 4a H Salix x sepulcralis Golden weeping willow 4a H Carya ovata Shagbark 4b var. chrysocoma

MMCatalpa speciosa Northern catalpa 4a H Styphnolobium japonicum Japanese pagodatree 5b

HMCrataegus crus-galli Cockspur hawthorn 4a HHSyringa pekinensis Peking lilac or Pekin lilac 4a

HHFraxinus americana* White ash 4a HHSyringa reticulata Japanese tree lilac 3a

H * European ash 4b HMTaxodium distichum Baldcypress 4b

HHFraxinus pennsylvanica* Green ash 2a H Ulmus glabra Scotch 4b

M Fraxinus quadrangulata* Blue ash 4a HMUlmus hybrids 4a-5

MMGinkgo biloba Ginkgo 4b Deciduous shrubs HHGleditsia triacanthos Thornless honeylocust 4a M Amelanchier canadensis Juneberry, serviceberry 3b var. inermis HHAmorpha fruticosa Indigo-bush 4b HHGymnocladus dioicus Kentucky coffeetree 4a M Aronia arbutifolia Red chokeberry 4b H nigra Black walnut 4b M Aronia melanocarpa Black chokeberry 3b H Larix decidua European 3a H Berberis koreana Korean barberry 4a H Larix kaempferi Japanese larch 4a H Berberis thunbergii Japanese barberry 4a H Larix laricina American larch, tamarack 2a H Buddleja davidii bush 5b HHLiquidambar styraciflua Sweet gum 5b (dieback )

MMNyssa sylvatica Black gum, tupelo, sour-gum 4b HHCaragana arborescens Siberian peashrub 2a

H deltoides Eastern cottonwood 3a M Clethra alnifolia Summersweet clethra 4b

H Populus grandidentata Bigtoothed 3a H Comptonia peregrina Sweet-fern 3b

H Populus tremula ‘Erecta’ Upright European aspen 2b MMCotoneaster apiculatus Cranberry cotoneaster 4b

H Populus tremuloides Quaking aspen 2a MMCotoneaster divaricatus Spreading cotoneaster 5b

H americana American 3b MMCotoneaster horizontalis Rockspray cotoneaster 5a

M Prunus maackii Amur chokecherry 3a MMCotoneaster acutifolius var. lucidus Hedge cotoneaster 3a M Prunus sargentii Sargent cherry 4b M Cotoneaster multiflorus Many-flowered cotoneaster 4b MMPrunus virginiana Chokecherry 3a H Euonymus alatus Winged euonymus, 4a-b M Pyrus calleryana Callery 4b burningbush

M Quercus alba White oak 3b HHHippophae rhamnoides Sprite common 4a ‘Sprite’ seabuckthorn MMQuercus bicolor Swamp white oak 4a

*No longer recommending planting ash (Fraxinus spp.) species (H = high level of tolerance; due to susceptibility to Emerald ash borer M = moderate level of tolerance) — 6— Deciduous shrubs Deciduous shrubs s p r a y s o i l z o n e s p r a y s o i l z o n e

H macrophylla Bigleaf hydrangea 5a-6 M Nannyberry viburnum 3a

H Hypericum kalmianum Kalm’s St. Johnswort 4a MMViburnum prunifolium Blackhaw viburnum 4a

M Ilex verticillata Winterberry, Michigan holly 3b M Viburnum opulus American cranberrybush 3a var. americanum viburnum H Lespedeza bicolor Shrub bush-clover (Viburnum trilobum) (dieback shrub) 5b H Vitex agnus-castus Chastetree (dieback shrub) 5b MHMorella pennsylvanica Northern bayberry 4a (Myrica pennsylvanica) H Yucca filamentosa Adam’s needle yucca 4b

H Perovskia atriplicifolia Russian sage (dieback shrub) 5a H Yucca filifera ‘Golden Sword’ Golden sword yucca 4b

M Philadelphus coronarius Mockorange 4b trees & shrubs H Dasiphora fruticosa Potentilla 3a M Chinese juniper 4a (Potentilla fruticosa) HHJuniperus communis Common juniper 3a H Prunus maritima Beach plum 3b HHJuniperus communis Common oldfield juniper 3a H Pyracantha coccinea Scarlet firethorn 5b var. depressa

H Rhodotypos scandens Black jetbead 5a HHJuniperus virginiana Eastern red-cedar 3b

HHRhus aromatica Fragrant 3b HMPicea pungens var. glauca Colorado blue 3a

HHRhus copallina Shining sumac, 4b H Pinus banksiana Jack pine 2a winged sumac H Pinus leucodermis Bosnian pine 4b HHRhus glabra Smooth sumac 3a HHPinus mugo Mugo pine 3a HHRhus typhina Staghorn sumac 3b H Austrian pine 4a MHRibes alpinum Alpine currant 3a H Pinus parviflora Japanese white pine 5a H Ribes odoratum Clove currant 4a H Pinus ponderosa Ponderosa pine 4a HHRobinia hispida Bristly locust (fruitless) 5b H Pinus sylvestris Scots or scotch pine 3a HHRosa rugosa Rugosa rose 2b

H Rosa virginiana Virginia rose 3b Groundcovers H Arctostaphylos uva-ursi Bearberry 2b H Goat willow 4a H Euonymus fortunei ‘Coloratus’ Purpleleaf wintercreeper 4b H Pussy willow 3a H Hedera helix English ivy 4b H Purpleosier willow, 3b blue willow HHJuniperus horizontalis Creeping juniper 3a

H Shepherdia argentea Silver buffaloberry 3a HHJuniperus sabina Savin juniper 3a

M Spiraea japonica Japanese spirea 3b HHJuniperus sargentii Sargent juniper 4a

M Spiraea nipponica Snowmound spirea 4a H Prunus pumila var. depressa Eastern sandcherry 4b ‘Snowmound’ (deciduous)

M Spiraea x vanhouttei Vanhoutte spirea 4a HHRhus aromatica ‘Gro-low’ Gro-Low sumac (deciduous) 3b H Symphoricarpos albus Common snowberry 3b V i n e s MMSyringa meyeri ‘Palibin’ Palibin lilac 4a H Campsis radicans Trumpetcreeper 4b

MMSyringa pubescens Miss Kim lilac 3b H Hedera helix English ivy 4b subsp. patula ‘Miss Kim’ H Parthenocissus inserta Woodbine 3b H Tamarix chinensis Tamarisk 2b H Parthenocissus quinquefolia Virginia creeper 3b M Viburnum dentatum Arrowwood viburnum 4a

— 7— ornamental grasses Herbaceous plants s p r a y s o i l z o n e s p r a y s o i l z o n e

H Calamagrostis x acutiflora Karl Foerster feather 4b H Eryngium x tripartitum Sea holly 5b ‘Karl Foerster’ reed grass M Euphorbia polychroma Cushion spurge 4a H Chasmanthium latifolium Northern sea oats 4b M Gaillardia x grandiflora Goblin blanket flower 3a M Festuca glauca ‘Elijah Blue’ Elijah Blue fescue 4a ‘Goblin’

M Helictotrichon sempervirens Blue oat grass 4a M tataricum German statice 4b

H Leymus arenarius ‘Glaucus’ Blue lyme grass 4a M Gypsophila paniculata Baby’s-breath 4a

M Miscanthus spp. Miscanthus, maiden grass 5a M Hemerocallis spp. Daylily 3b

H Panicum virgatum Switch grass 4b M Heuchera micrantha Palace Purple coral bells 4a ‘Palace Purple’ H Pennisetum alopecuroides Fountain grass, pennisetum 5a M Heuchera sanguinea Chatterbox coral bells 4a M Schizachyrium scoparium Little bluestem 4a ‘Chatterbox’

M Hosta plantaginea Fragrant hosta, August lily 4a Herbaceous plants M Hosta undulata Variegated hosta, 3b M Achillea millefolium Apple Blossom 3b ‘Medio-variegata’ wavy hosta ‘Apple Blossom’ common yarrow M Iberis sempervirens Evergreen candytuft 5a M Achillea ‘Moonshine’ Moonshine yarrow 3b M Iris sibirica ‘Caesar’s Brother’ Caesar’s Brother Siberian iris 3b H Allium christophii Stars of Persia 4b M Iris spp. (Germanica Group) Bearded iris 3b H Allium senescens Ornamental onion 3b M Kniphofia ‘Royal Standard’ Red-hot poker 5b-6 H Anthemis punctata Anthemis 5b subsp. cupaniana M Leucanthemum x superbum Becky shasta daisy 4a ‘Becky’ H Armeria maritima ‘Splendens’ Splendens sea thrift 4a M latifolium Purple sea lavender 4a M White sage 4a M Liriope spicata Creeping lilyturf 5b M Artemisia ‘Powis Castle’ Powis Castle artemisia 5b M Nepeta x faassenii Nepeta, catmint 4a M ‘Nana’ Dwarf silvermound 3b artemisia M Oenothera fruticosa Sundrops 4a subsp. glauca M Beach wormwood 4a M Oenothera macrocarpa Silver evening primrose 4a M Aster novae-angliae Purple Dome 4a ‘Purple Dome’ New England aster M Penstemon spp. Beardtongue 3b-4a

M Bergenia cordifolia Heart-leaf bergenia 3b MMPhlox subulata Creeping phlox (evergreen) 4a

M Catananche caerulea Cupid’s dart 4b M Physostegia virginiana Obedient plant 3a

M ruber Jupiter’s beard, red 5a M Saponaria ocymoides Rock soapwort 4a

H Crambe maritima Sea kale 5a M Sedum spp. Stonecrop 3b-4

H Dianthus x allwoodii ‘Helen’ Helen allwood pinks 4a M Sedum ‘Herbstfreude’ Autumn Joy sedum 3b

M Dianthus gratianopolitanus Cheddar pinks 4a M Sempervivum spp. Hens and chicks 4a

H Echinops spp. Globe thistle 4a M Sidalcea malviflora Prairie mallow 4b

H Erigeron glaucus Seaside aster, 4a M Thymus spp. Thyme 5b fleabane M Veronica incana Woolly speedwell 3b H Eryngium x oliverianum Sea holly 4a M Waldsteinia ternata Barren strawberry 3b

(H = high level of tolerance; M = moderate level of tolerance)

— 8— Ta b l e 2 . Products available for ice control (not including products used only in airports) p r o d u c t a d v a n t a g e s disadvantages

Sodium chloride (NaCl) • Effective, melts snow, penetrates ice • Highly corrosive • Low cost • Accumulates in soil • Dissolves easily • Damages soil structure • Readily available • Injurious to plants • Easy to remove residue from floors • Readily leaches and contaminates and carpets groundwater • Increases runoff of heavy metals • Increases soil erosion • Ineffective at temperatures below 20°F

• Highly corrosive, but anti-corrosive Calcium chloride (CaCl2) • Effective to –20°F • Works better at lower temperatures than compounds can be added NaCl • Costs about 10 times more than NaCl • Dissolves faster than NaCl at lower • Injurious to plants temperatures • Readily leaches into groundwater • Releases some heat when dissolved • Requires special storage and handling • Won’t damage soil structure to prevent caking • Often included in commercial • Tends to keep pavement wet blended products • Leaves greasy stains on carpets and dulls • No visible residue on plants when dry floors from shoes • Causes skin irritation—must wear protective clothing when applying • Damages leather gloves and shoes

• Highly corrosive, but anti-corrosive Magnesium chloride (MgCl2) • Effective to 0°F • Dissolves easily and faster acting than compounds can be added NaCl • Costs about 10 times more • Works better at lower temperatures than than NaCl NaCl • Injurious to plants • Won’t damage soil structure • Readily leaches into groundwater • Available with corrosion inhibitors • Requires special storage and handling to prevent caking • Tends to keep pavement wet • Leaves greasy stains on carpets and dulls floors from shoes

Potassium chloride (KCl) • Used as a commercial fertilizer • Highly corrosive • Dissolves easily • Costs about 10 times more • Won’t damage soil structure than NaCl • Easy to handle and store • High salt index and potential to burn foliage and roots • Easy to remove residue from floors and carpets • Readily leaches into groundwater • Limited use • Ineffective at temperatures below 25°F

Potassium acetate (K-acetate) • Produced from renewable resources • Very expensive • Effective to –25°F • Only available as a liquid; requires • Biodegradable liquid application equipment • Safe for the environment and plants • Not commonly available • Non-corrosive • Won’t damage soil structure • More desirable than urea or glycol for airport application

— 9— Ta b l e 2 . Products available for ice control (not including products used only in airports), continued p r o d u c t a d v a n t a g e s disadvantages

Urea or nitrogen salts • Used as a commercial fertilizer • May be corrosive if using high ammonia such as ammonium sulfate • Lower burn potential than KCl content • Expensive [(NH4)2SO4], or potassium • Less damaging to plants than NaCl • May cause concrete degradation nitrate (KNO3) • Melts snow, but not commonly used • Non-corrosive (if use lower ammonia • Reduced effectiveness below 25°F content) • High potential for nitrogen runoff to surface water • Runoff promotes weed growth and eutrophication of lakes • Readily leaches into groundwater • Toxic to fish and animals

Calcium magnesium acetate • Made from dolomitic limestone and • Costs approximately 40 times more (CMA) acetic acid than NaCl • Biodegradable • Ineffective at temperatures below 20°F, • Does not harm plants in freezing rain, and on dry snow • Won’t damage soil structure • Poor at removing existing ice • Can increase soil permeability • Can leach into surface water (lakes and ponds), degrading water quality • Adds calcium and magnesium to soil • Leaves a slight greasy film on carpets • Less corrosive than other deicing salts • Less likely to leach into groundwater • Can be used in environmentally sensitive areas • Does not bond to pavement, so snowplow can scrape aside dry snow

Agricultural by-products • Non-corrosive and reduces corrosiveness • Expensive and adds cost to chemical from processing of sugar beets or when mixed with chloride-containing deicing mixtures deicers processed corn or by-products from beer • Only available as a liquid . Product can be used as a pre- • Increases equipment life • Purity of product and amount of smell wetting liquid for deicing salts, or as a • Reduces deicing salt consumption and varies between agricultural by-products labor costs used component of a liquid deicing salt brine solution. • Less harmful to plants as less deicing salt • May contain high phosphates (depends is needed on product) • Biodegradable (before mixed with • Very sticky material that can track under deicers) foot and vehicle traffic • Adheres well to dry surfaces thereby pre- • Some blends may have high biological venting ice and snow from sticking to oxygen demand* and could remove pavement oxygen from surface waters if not fully • Mixes well with other liquid chemicals biodegraded before entering surface water • Improves ice melting of chloride-contain- ing deicers when mixed with it • Greater low temperature performance when mixed with deicers • No dust-causing are needed

*Biological oxygen demand is a measurement of the oxygen consumed by microorganisms decomposing organic matter in water. This would primarily be a concern in ponds and lakes.

— 10 — Ta b l e 2 . Products available for ice control (not including products used only in airports), continued p r o d u c t a d v a n t a g e s disadvantages

Abrasive materials • Low initial cost • Does not melt ice or snow (sand, crushed aggregate, slag, • Readily available • Traffic reduces its effectiveness bottom ash, kitty litter, cinders) • Does not harm plants (blown off, pushed off into snow) • Non-corrosive • Covered by new snow • Useful at lower temperatures when • Does not work well on hard ice deicing chemicals become less effective • Not as effective as deicing salts at • Improves traction for vehicles preventing skids and pedestrians • Requires reapplication, leading to more • Works immediately upon application equipment trips per mile than NaCl • Accumulates and clogs gutters and drains; must be removed • Can chip and scar windshields if kicked up by traffic • Some abrasives create dust problems after storms and can contribute to particulate air pollution (ash fines)

— 11 —  winter salt injury and salt-tolerant landscape plants Sources of information Deeter, L. 2001. Salt tolerance of herba- Walsh, M.B. 1998. In search of salt-tolerant ceous perennials. Greenhouse Product plants. Landscape Contractor 9:10–14. News 11(6):52, 54–55. Zimmerman, E.M., and L.G. Jull. 2006. Friederici, P.2004. Salt on the earth: How Sodium chloride injury on buds of Acer snow control has created high-sodium platanoides, cordata, and Viburnum landscapes that favor a few, invasive lantana. Arboriculture and Urban Forestry species. Chicago Wilderness Magazine. 32(2):45-53. Winter 2004, Zimmerman, E.M., L.G. Jull, and A.M. Shirazi. http://chicagowildernessmag.org/ 2005. Effects of salinity and freezing on issues/winter2004/salt.html. Acer platanoides,Tilia cordata, and Lumis, G.P.,G. Hofstra, and R. Hall. 1975. Salt Viburnum lantana. Journal of damage to roadside plants. Journal of Environmental Horticulture 23(3): Arboriculture 1:14–16. 138–144. Percival, G.C. 2005. Identification of foliar salt tolerance of woody perennials using chlorophyll fluorescence. HortScience 40(6):1892–1897. The Morton Arboretum. 2003. Salt tolerant trees and shrubs. Bulletin No. 630-968- 0074. http://www.mortonarb.org Tree City USA. 1998. Let’s stop salt damage. Tree City USA Bulletin No. 32.

Copyright © 2009 by the Board of Regents of the University of Wisconsin System doing business as the division of Cooperative Extension of the University of Wisconsin-Extension. All rights reserved. Send copyright inquiries to: Manager, Cooperative Extension Publishing, 432 N. Lake St., Rm. 227, Madison,WI 53706. Author: Laura G. Jull is associate professor of horticulture, College of Agricultural and Life Sciences, University of Wisconsin-Madison and University of Wisconsin-Extension, Cooperative Extension. Produced by Cooperative Extension Publishing, University of Wisconsin- Extension. Cooperative Extension publications are subject to peer review. Reviewers: Dr. Abbas Shirazi was researcher at Morton Arboretum in Lisle, Illinois. Dr. Laura Deeter is associate professor, Agricultural Technical Institute,The Ohio State University,Wooster, Ohio. Mr. Don Walker is professor emeritus, Department of Engineering Professional Development, University of Wisconsin-Madison. Ms. Barb Larson is Kenosha County horticulture educator, University of Wisconsin-Extension. An EEO/AA employer, the University of Wisconsin-Extension, Cooperative Extension provides equal opportunities in employment and programming, including Title IX and Americans with Disabilities Act (ADA) requirements. This publication is available from your Wisconsin county Extension office or from Cooperative Extension Publishing.To order, call toll-free: 1-877-WIS-PUBS (947-7827) or visit our web site: learningstore.uwex.edu.

winter salt injury and salt-tolerant landscape plants (A3877) I-04-2009

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