Q & A from the Miller Library ’ s Plant Answer Line
SALT-TOLERANT PLANTS AND SEAWEED MULCH IN THE GARDEN
B y R e b e c c a A l e x a n d e r | P h o t o s b y N i a l l D u n n e
This regular column features Q & A selected and adapted from the Elisabeth C . Miller Library ’ s Plant Answer Line program . If you ’ d like to ask a plant or gardening question of your own , please call ( 206 ) 897-5268 ( UW Plant ), send it via the library website ( www . millerlibrary . org ), or email directly to hortlib @ uw . edu .
QUESTION : I need plant suggestions for growing in cold , salty winds only 15 to 20 feet from the high water mark of the Salish Sea . In winter , the salt water from the ocean occasionally douses the area where I will be gardening . I ’ m particularly interested in perennials and small shrubs .
ANSWER : Salt spray from the sea can directly damage terrestrial plant foliage ( leaf burn ) and also alter the salinity of the soil , potentially interfering with water uptake by plants and causing soil compaction . Many conventional garden plants are sensitive to saline conditions and should be avoided by people gardening on shoreline or bluff properties . To create a healthy coastal garden , it ’ s best to grow salt-tolerant plant species .
The Washington State University publication “ Spotlight on Shoreline Planting ” ( 2015 ) has some great information on shoreline landscaping and native plants adapted to shoreline conditions . “ Some of the better salt-tolerant shrubs and small trees to consider include salal ( Gautheria shallon ), ocean spray ( Holodiscus discolor ), snowberry ( Symphoricarpos albus ), elderberry ( Sambucus species ), tall Oregon grape ( Mahonia aquifolium ), serviceberry ( Amelanchier alnifolia ), Nootka rose ( Rosa nutkana ), and wax myrtle ( Myrica [ now called Morella ] californica ).”
“ A variety of native [ herbaceous ] plants are commonly found near the shoreline and typically
do well in the Puget Sound area . These include the sword fern ( Polystichum munitum ), coastal lupine ( Lupinus littoralis ), honeysuckle ( Lonicera species ), and coastal strawberry ( Fragaria chiloensis ).”
Washington Native Plant Society ’ s list of plants for various habitats is also useful . Visit their website at www . wnps . org / native-gardening / resources # habitat and scroll down to find “ Plants for Saltwater Shoreline and Saltwater Habitats .” Recommended perennials include graceful cinquefoil ( Potentilla gracilis ) and the iris-like golden-eyed grass ( Sisyrinchium californicum ).
Frances Tenenbaum ’ s “ Gardening at the Shore ” lists shrubs and perennials , including grasses . Following are some plants smaller than 20 feet tall that might work in our region .
Shrubs : Acca ( Feijoa ) sellowiana ( 8 – 12 feet ); Arctostaphylos uva-ursi ( ground cover ); Atriplex canescens ( 3 – 5 feet ); Baccharis halimifolia ( 6 – 10 feet ); Calluna vulgaris ( from 6 inches to 2 feet ); Caryopteris × clandonensis ( 2 – 3 feet ); Ceanothus species ; Chamaecyparis lawsoniana ( look for a dwarf variety of this tree , such as ‘ Blue Surprise ’); Clethra alnifolia ( 8 feet ); Hydrangea macrophylla ( 6 – 8 feet ); Rhus typhina ( 15 feet ); Rosa rugosa ( 6 feet ); Syringa vulgaris ( 20 feet ); Vaccinium corymbosum ( 12 feet ); Viburnum ( numerous species of different sizes ).
Perennials : Achillea ; Armeria maritima ; Artemisia schmidtiana ; Asclepias tuberosa ;
24 v Washington Park Arboretum Bulletin