A spate of storms last winter caused serious problems for some coastal properties, and as sea levels rise, the violent storms and flooding are almost certain to get worse. So I wasn’t entirely surprised when Robert and Cathy Gordon emailed me asking what they should do about landscaping around their longtime home, which sits on coastal marshland in Kennebunkport.
For the past 40 years, native shrubs have grown about 10 feet from their home on the marsh-side of the property, they wrote. Between those and the house is a patch of “regular grass and weeds that we mow on a regular basis,” they wrote (which sounds a lot like the lawn situation at our house). But after four decades, that section of lawn was covered with a foot of salt water from storms several times last year. And it has died.
I phoned State Horticulturist Gary Fish to ask how people who find themselves in a similar position can remove salt from the soil. He advised that they water heavily without swamping their plants, to get the salt to leach out below the root zone, and counteract the salt with an application of pelletized gypsum. If the property never got covered with salt water again, these suggestions would work perfectly. These days, that’s a big if. Reports of climate-caused rising sea levels make such thoughts overly optimistic.
Before emailing me for advice, the Gordons came up with a few ideas on their own. Maybe they should cover the entire area with stone. Sure, that might work but it sounds dull, plus it’s not gardening, so I’m going to ignore it. Their other idea came closer to the mark: “to plant seeds such as bluestem, prairie dropseed, switchgrass etc. that can be mowed to about a 3-inch level,” they wrote. That should work, but personally, I’d find it almost as boring as the typical lawn of Kentucky bluegrass.
Fish provided me with a list of 31 plants that can survive infrequent doses of salt water. It includes the bluestem and switchgrass the Gordons mentioned. The plants are mostly natives. Nothing will survive constant inundation, however.
One plant Fish suggests is especially tough even faced with salt water? Cattails – their horticultural name is Typha latifolia. But as often happens, one problem begets another. While cattails are native, they are aggressive and could easily out-compete other plants in the landscape.
Looking at the list of salt-tolerant plants, I thought about what I’d do if I were designing the Gordons’ yard for flood resistance. I’d start with some small shrubs. Although they can’t be mowed, obviously, they would provide color and texture along the edges of the plot. I’d plant a dogwood, too. Red-twig dogwood, which my wife and I have grown in our garden for decades, looks good all winter, and some varieties have attractive variegated foliage. Its gray dogwood cousin also stands up to salt water, and has berries that offer nice winter color.
Serviceberry (also called shadbush or amelanchier) is another tough shrub with berries. If the Gordons like the idea of a native evergreen, I’d suggest a juniper, maybe the 6-inch-tall “Bar Harbor” or “Blue Rug” creeping varieties or what native Mainers call red cedar, which will grow to 20 feet. Pitch pine, which is found wild all along the coast, is another option.
Joe Pye weed, which has the botanical name Eupatorium, is a native that is having a banner year in many gardens. This herbaceous perennial can grow 7 feet tall, and its long-lasting purple flowers are a magnet for pollinators. Mountain mint is another pollinator magnet that may work in an area threatened by salt water. It has dense white flowers and, like most mints, will spread if you let it.
I was surprised to see that daylilies are listed among the top 10 salt-tolerant plants by Nature Hills Nursery in Nebraska. There the problem would be road salt, not the rising seas.
When I decided to write this column, my wife, Nancy – who has a better memory than I do – found our copy of “Seascape Gardening’ by Anne Moyer Halpin. The book gives a lot of advice on which plants are tough enough to withstand the fierce winds, blowing sand, strong sun and other elements at the water’s edge, and how to design with them.
She includes sections on two Maine gardens that sit very near the coast – Brave Boat Harbor Farm in York and Snug Harbor Farm in Kennebunk. The book was published in 2006, so no doubt much has changed in those gardens since then, but the planting and plant information are still on target.
Tom Atwell is a freelance writer gardening in Cape Elizabeth. He can be contacted at: tomatwell@me.com.
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