Deb Terrill is a syndicated columnist who monitors moths for The Nature Conservancy.

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Standing Up to Salt
by Deb Terrill       #Advice


Northern bayberry (Myrica pensylvanica) can stand up to winter salt, but there are also many other options.

It’s no accident that a list of salt-tolerant plants reads a bit like a list of seaside plants. Without even looking at lists of such plants compiled by arboretums and universities, I can begin my own list from memory. Past walks along the coast of Cape Cod provide me with a mental image of plants that live in constant sea spray.

Rosa rugosa, the rugged wild rose, bayberry, with its waxy white berries and white oak are the first to come to mind. No temperate-zone beach seems to be without these ubiquitous natives. Black locust, yucca, Montauk daisies, pitch pine and black pine abound in the cottage gardens.

Here in the Midwest, we don’t get a lot of sea spray, but we surely do get our share of salt. When the roads begin to ice up in late fall, the salt trucks are out, and the white residue can be seen everywhere – on our cars, on our dark-colored coats and on the roadways. It builds over the winter, and plants along busy, fast-moving roads get coated repeatedly. Anyone who has ever followed a semi-truck down the highway knows that whatever is on the road gets blasted into the air with each vehicle that passes.

This airborne salt spray has a toxic effect on certain plants, causing the cells to break down and dry out. Sometimes, as in the case of deciduous trees, this airborne salt does little to harm the plant, and in other cases, like that of white pine, it can ruin the appearance of the plant and even kill it. But airborne salt is only half of the problem.

When the snow melts in the spring, all of the salt on the surface percolates down into the soil, where it is comes into contact with plant roots. This is actually more harmful to many plants than the airborne spray. Soil salt can burn roots, become toxic to plants and render them unable to take up water. Homeowners on the quietest of streets may experience damage from soil salt when plowed snow from streets and salted sidewalks melts into their landscapes.

Plants break dormancy early in the spring, around March, and road salting may still take place throughout that month and even into April. When plants become active and salt is still being applied, it is a recipe for distress.

How to Know

It is not always easy to recognize salt injury. It may be evident on evergreens when the side of the plant exposed to salt spray turns brown, but soil salt can also cause bud and shoot death all over evergreens, or on certain seemingly random branches.

In deciduous plants, repeated salt injury can cause everything from failure to flower, dieback at the ends of branches and leaves that begin to look burned in the late summer, when soil moisture is low, and the salt is concentrated.

What to Do

While there is little you can do to remedy salt damage in large expanses of plantings along busy roadways, homeowners can take some remedial action. We can limit the amount of salt we use on porches, steps, sidewalks and driveways, opting for sand or birdseed instead.

We can also flood the soil with water from the hose soon after it has thawed, thereby diluting the salt concentration in the soil. This is especially important after March 1, when salt is applied after plants have broken dormancy.

Selecting for Prevention

Perhaps the best prevention, whenever possible, is to select plants that are salt-tolerant. We can do this in new plantings and when we replace plants that have died or become disfigured. I have found that various organizations provide lists that are somewhat different, but there is a good number of plants that they all have in common. 



 Feather Reed Grass ( Calmagrostis acutiflora ‘Karl Foerster’)
 

Salt-Tolerant Perennials

Sea thrift (Armeria maritima)
Feather reed grass (Calmagrostis x. acutiflora ‘Karl Foerster’)
Helen Allwood pinks (Dianthus pulminarius x allwoodii)
Blue lyme grass (Elymus arenarius)
Sea lavender (Limonium latifolium)
Fountain grass (Pennisetum alopecuroides)

Perennials With Moderate Tolerance

Nodding Onion (Allium cernuum)
Powis Castle Artemisia (Artemisia  ‘Powis Castle’)
Silver Mound artemisia (Artemisia schmidtiana ‘Silver Mound’)
Elijah Blue fescue (Festuca glauca  ‘Elijah Blue’)
Stella de Oro daylily (Hemerocallis ‘Stella de Oro’)
Palace Purple coral bells (Heuchera villosa ‘Palace Purple’)
Hosta (Hosta plantaginea cvs.)
Lilyturf (Liriope spicata)
Virginia creeper (Parthenocissus quinquefolia)
Autumn Joy sedum (Sedum ‘Herbstfreude’)


Salt-Tolerant Evergreens

Evergreens are the most susceptible to injury since their foliage is present throughout winter and their roots get saturated by salt in the spring thaws. These are the most tolerant evergreens:

Junipers, most varieties and species
Norway spruce (Picea abies) – tolerant of airborne spray and soil salt
White spruce (Picea glauca) – tolerant only of airborne salt spray
Colorado blue spruce (Picea pungens)  – tolerant only of airborne salt spray
Mugo pine (Pinus mugo) all cultivars
Black pine (Pinus nigra)
Pitch pine (Pinus rigida)


Mugo pine (Pinus mugo)

Salt-Tolerant Deciduous Trees

Norway maple (Acer platanoides)
Serviceberry (Amelanchier spp.) – tolerant only of airborne salt spray
Russian olive (Elaeagnus angustifolia)
White ash (Fraxinus americana)
Honeylocust (Gleditsia triacanthos)
Sweetgum (Liquidambar styraciflua)
Honeysuckle (Lonicera sempervirens)
White oak (Quercus alba)
Swamp white oak (Quercus bicolor)
Bur oak (Quercus macrocarpa) – less tolerant of soil salt
Black locust (Robinia pseudoacacia)
Japanese tree lilac (Syringa reticulate)
Bald cypress (Taxodium distichum)


Honeyrose honeysuckle (Lonicera ‘Honeyrose’)

Salt-Tolerant Shrubs

Barberry (Berberis spp.)
Cotoneaster (Cotoneaster cvs.)
Forsythia (Forsythia cvs.)
Bayberry (Myrica pensylvanica)
Fragrant sumac (Rhus aromatica ‘Gro-Low’ and R. typhina)
Alpine currant (Ribes alpinum)
Rosa rugosa and an array of rugosa-related landscape roses
Dwarf Korean lilac (Syringa ‘Palabin’ and  ‘Miss Kim’) 


Dwarf Korean lilac (Syringa meyeri ‘Palibin’)

 

From Chicagoland Gardening Volume XXI Issue IV. Photos courtesy of Bailey Nurseries.

 

Posted: 02/12/14   RSS | Print

 

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