Gardening by the Sea: Perennials

Posted in Gardening Tips on November 5 2013, by Sonia Uyterhoeven

“I must go down to the seas again, to the lonely sea and the sky,
And all I ask is a tall ship and a star to steer her by …
I must go down to the seas again, for the call of the running tide
Is a wild call and a clear call that may not be denied; …”

While John Masefield’s lyrical poem conjures the image of being at one with the open sea, one year after Hurricane Sandy many seaside inhabitants have developed a very different relationship with their neighbor.

Last year we looked at salt water remediation in the Storm Clean-Up 101 series, which included everything from tips on soil testing, to a comprehensive clean-up task list for gardeners. With a year behind us and the gardening season gone, coastal inhabitants may now have time to assess their gardens and evaluate their garden’s needs for restoration and remediation in the spring.

While aesthetics and maintenance are standard considerations in garden design, coastal gardens are also tasked with erosion control. Seascapes are continuously battered by winds and waves. Shifting sand on beaches and primary dunes are part of a natural process, but that doesn’t mean humans shouldn’t intervene in helping to stabilize these natural formations.

Plants are the best way to stabilize dunes and protect waterfront properties from storm damage. Seaside plants have extensive root systems that help bind the sand and keep it in place. They also help to create wind breaks and protective areas for the garden.

Seaside plants not only provide homeowners with a protective barrier from the sea, but they also help protect the oceans. Well thought out seaside plantings can keep coastal water clean by trapping and filtering sediment and run-off from landscapes and roadsides.

When planting a seaside garden it is important to use tough plants for outer perimeter wind breaks and to select salt tolerant or halophytic plants for vulnerable spots in your garden–whether it is an area that is prone to flooding or places that are constantly battered by salt spray. Desiccation from intense heat and bright light is another coastal concern. In addition, while sandy soil is porous and provides excellent drainage, it often lacks available nutrients and has poor moisture retention.

Many plants have adapted to this type of hostile environment. Waxy coatings and glossy foliage on plants help repel salt water and protect plants from salt spray. Plants with thick foliage tend to withstand storm damage well. Plants adapted to xeric environments that have silver or gray foliage are protected from intense sunlight. Small-leaved plants also tend to be less prone to desiccation and handle dry sites better. Succulent plants with water-filled tissue are well equipped to handle dry sites.

Below is a check list for landscaping coastal gardens, and a plant list with many perennial options.

General Landscaping Check List for Coastal Gardens:

1. Plant a buffer area of deep-rooted native grasses and shrubs between your garden and the shore to help slow erosion.

2. Grade your property so that storm water does not flow down to the dunes and beaches, increasing erosion. Direct storm water away from the shoreline.

3. Plant the perimeter of your garden with salt-tolerant plants that can tolerate both wet and dry soil.

4. Plant areas around patios and driveways with plants that will slow storm water run-off.

5. Use biodegradable erosion fabric on steep slopes to give stability while plants take time to get established.

6. Add compost to new plantings in your garden to provide added nutrients. Do not add compost to dunes.

7. Do not mulch garden beds in areas adjacent to dunes where the mulch is in danger of being washed away.

8. The best planting time is spring or fall when there is a higher level of rainfall and days are cooler. Beach grass, Ammophila breviligulata, can be planted in late fall into the winter.

9. Keep lawn areas small. Plant fescue grasses that require less water and fertilizers than blue grass.

10. Plant beach grass on dunes that parallel the coastline. Dunes should ideally be 40 to 50 feet wide but can be a minimum of 20 feet wide. Beach grass traps sand and builds a dune to protect your coastal garden. Beach grass rhizomes spread, colonizing the area and stabilizing the dune.

On primary dunes you will find American beach grass, Ammophila breviligulata growing. Generally, on the back side of dunes and in protected swales between dunes, the vegetation diversifies to include tough seaside options such as seaside goldenrod Solidago sempervirens, bearberry Arctostaphylos uva-ursi, eastern prickly pear cactus Opuntia humifusa, beach plum Prunus maritima, and bayberry Myrica/Morella pensylvanica.

Below is a list of perennials and ground covers that will work well in seaside gardens. Next week we will take a look at woody plant options for seaside gardens. The list is separated into Belt 1 Plants that tolerate the elements well and can be planted close to the beach, and Belt 2 Plants that need some protection from the sea.

A few ground covers with good salt tolerance that thrive in sandy soil are:

Bearberry Arctostaphylos uva-ursi
Broom crowberry Corema conradii
Cliff green Paxistima canbyi

Belt 1 – Some perennials that can tolerate a great deal of wind, salt spray and sand include:

American beach grass Ammophila breviligulata
Blue stem Andropogon gerardii
Western mugwort Artemisia ludoviciana ‘Valarie Finnis’ – note: many of the Artemisia are aggressive and should be avoided. The two listed here are well-behaved.
Sea pink Armeria maritima
Wormwood Artemisia ‘Powis Castle’
Scotch heather Calluna vulgaris
Lavender Lavendula
Sea lavender Limonium carolinianum
Eastern prickly pear cactus Opuntia humifusa
Seaside goldenrod Solidago sempervirens
Yucca Yucca sp.

Belt 2 – There are a large number of perennials that can tolerate some wind, salt spray and sand but perform best in areas that offer some protection from the sea. Here are some options to consider:

Yarrow Achillea millefolium and A. filipendulina
Hollyhock Alcea rosea
Blue star Amsonia sp.
Butterfly weed Asclepias tuberosa
New England aster Symphyotrichum novae-angliae
Showy aster Eurybia spectabilis
Basket of gold Aurinia saxatilis
False indigo Baptisia australis
Clematis Clematis sp.
Tickseed Coreopsis sp.
Pinks Dianthus
Coneflower Echinacea
Globe thistle Echinops
Heath Erica carnea
Sea holly Eryngium maritimum
Flowering spurge Euphorbia corollata
Blanket flower Gaillardia sp.
Baby’s breath Gypsophila paniculata
Daylily Hemerocallis
Rose mallow Hibiscus moscheutos
Blue flag iris Iris versicolor
Torch lily Kniphofia
Shasta daisy Leucanthemum x superbum
Purple moor grass Molinia
Beebalm Monarda
Catmint Nepeta
Switch grass Panicum virgatum
Russian sage Perovskia atriplicifolia
Garden Phlox Phlox paniculata
Black-eyed Susan Rubeckia hirta
Stonecrop Sedum spectabile
Lamb’s ears Stachys byzantina
Periwinkle Vinca minor