High soluble salts in soil can harm plants by reducing water uptake, which leads to foliage burn, restricted root growth, and fewer blooms. Sensitivity varies by species, with seeds and seedlings being most vulnerable.
Salt levels become elevated due to excess fertilizer, pet urine, de-icing salts, and poor-quality irrigation water, among other factors. To lower high levels, irrigate heavily to leach salts.
Soils with many soluble salts (ions) dissolved in the soil water conduct electricity much better than pure water. Because of this, the electrical conductivity of the soil (measured in millimhos per centimeter or mmhos/cm) is used to measure the concentration of soluble salts present.
Salt Tolerance of Selected Garden Plants
How plants react to soluble salts in the soil depends on how sensitive they are to elevated concentrations. Some species, such as asparagus, are very tolerant of excess soluble salts, while others, like white pine, are highly intolerant of elevated levels. Additionally, seeds and seedlings of nearly any species are some of the most vulnerable to excess soluble salts.
Soluble salts at 2 mmhos/cm (millimhos per centimeter) or less require no action. Sensitive plants will begin to see damage above 2 mmhos/cm, moderately tolerant plants above 4 mmhos/cm, and tolerant plants above 8 mmhos/cm.
Plants Highly Sensitive to Soluble Salts
These species will see damage if levels exceed 2 mmhos/cm.
- Alder
- Azalea
- Beech
- Begonia
- Blueberry
- Carrot
- Cotoneaster
- Green Bean
- Kentucky Bluegrass
- Norway Spruce
- Onion
- Pea
- Radish
- Rapsberry
- Red Pine
- Strawberry
- Sugar Maple
- Viburnum
- White Pine
- Yew
Plants Moderately Tolerant to Soluble Salts
These species will see damage if levels exceed 4 mmhos/cm.
- Apple
- Birch
- Black Walnut
- Cabbage
- Catalpa
- Celery
- Creeping Bentgrass
- Cucumber
- Elm
- Grape
- Forsythia
- Ginkgo
- Hackberry
- Kentucky Coffeetree
- Lettuce
- Linden
- Magnolia
- Norway Maple
- Pepper
- Perennial Ryegrass
- Potato
- Red Fescue
- Red Maple
- Redbud
- Rose
- Snapdragon
- Sweet Corn
- Sycamore
- Tulip Tree
Plants Tolerant to Soluble Salts
These species will see damage if levels exceed 8 mmhos/cm.
- Beet
- Black Locust
- Boxwood
- Broccoli
- Chrysanthemum
- Cottonwood
- Crabapple
- Geranium
- Honeylocust
- Marigod
- Muskmelon
- Red Oak
- Spinach
- Squash
- Tall Fescue
- Tomato
- White Ash
- White Oak
- Zinnia
Plants Highly Tolerant to Soluble Salts
These species will see damage if levels exceed 16 mmhos/cm.
- Arborvitae
- Asparagus
- Juniper
- Russian Olive
- Swiss Chard
Additional Resources
- Salinity and Plant Tolerance, Utah State University (PDF)
- Trees and Shrubs that Tolerate Saline Soils, Salt Spray, and De-icing Salts, Virginia Tech (PDF)
- Soil Test Interpretations and Fertilizer Management for Lawns, Turf, Gardens, and Landscape Plants, University of Minnesota (PDF)
- An Index of Salinity and Boron Tolerance of Common Native and Introduced Plant Species in Texas, Texas A&M (PDF)
- Managing Salt-affected Soils for Crop Production, Oregon State University
More Information
- How to Interpret Soil Test Results
- Using Deicing Salts in the Home Landscape
- Soil Testing Resources for Home Gardeners
- Managing Garden Soil
- Fertilizing in the Home Garden
Photo credit: Oskars AdobeStock