By DEBORAH G. SCANLON
Rockweed
Pine needles, wood chips, leaves, and seaweed have been simple but valuable resources for Cape Cod gardeners for generations.
Seaweed, in fact, has had many uses over the years. Our grandparents shared stories of it being used in the past as insulation, piled high along the foundations of houses in the winter to keep out the cold. And a key ingredient to family clambakes was the rockweed that we put on the stones in the fire pit on the beach before steaming the lobsters, clams, potatoes, and corn.
An unusual application of seaweed was in the news in the 1950s, when the Bugeye ketch, Brown Smith & Jones, sank at the Eel Pond town dock in Woods Hole. The first step in raising the boat was to plug some of the bigger leaks with seaweed and other substances to caulk the gaping seams. Six big pumps going full tilt finally raised the ship.
But perhaps the most common use over the years has been in our gardens as mulch and fertilizer. Loaded with nutrients, it covers the weeds and blocks new ones, and keeps moisture in the soil.
On a Facebook Cape Cod gardening site, people praised seaweed’s value, whether putting it directly into the compost or in a pile for the rain to rinse the salt off, then placing it in the garden. But ecological concerns were also raised.
Seagrass
Javier Lloret, research scientist at the Marine Biological Laboratory Ecosystems Center, explained that on the Cape “eelgrass is in decline… the mats of eelgrass leaves and remains that we usually find on the local beaches are playing very important ecological services, not only providing food and refuge for many organisms (sand fleas for example), but also by protecting our beaches against erosion. The mat of dead eelgrass leaves and rhizomes mixed with sand and gravel forms a very effective barrier against waves and storms….”
As for the difference between seaweed and seagrass, he said: “In general, seaweed is algae, while seagrass refers to vascular plants; plants with roots, leaves, and flowers. Seagrasses are not algae. They are grasses, like the ones in our backyard, that some time ago evolved and (re)colonize shallow seas.
“Both seagrasses and algae play important ecological roles. The scientific community has paid a lot of attention to seagrasses and their roles, in part because they have been disappearing or experiencing degradation in many parts of the world. Algal communities are also important, although they may have received less attention.”
The question then is, can people use it responsibly?
Dr. Lloret said he didn’t think that “a few people taking a couple of bags of this material (whether it is seagrass remains, or algae, or mixed) for their gardens can have a substantial impact on the ecosystem. I do see a problem if, somehow, some locations become ‘popular,’ and people start going to those same places on a regular basis to collect it.”
Use it only for a small area of the garden, a friend suggests, and be careful not to collect too much, and take it from an area where there is a good supply. Leave lots more than you take away.
Terry Soares, of Soares Garden Nursery, suggested a method that uses seaweed sparingly. “For a vegetable garden, you don’t need a lot of seaweed. On the empty rows between your plants, put down a layer of newspaper (black and white—no color or glossy paper) and put seaweed on top of that. It will last two years.”
Requests for town regulations regarding seaweed removal were not returned before this article’s publication. Gardeners should check with local agencies.
Wood Chips
Pine needles are a great resource for acid-loving plants like azaleas and boxwood, Ms. Soares said. Another trend, she added, is to grind up your leaves with the lawn mower and use this as mulch. “Leaf mulch also protects and sustains pollinators,” she said. “And ground-up leaves don’t blow away.”
George Chapman, for whom horticulture is both his profession and hobby, said he used seaweed in the past but always wondered about its environmental impact. He thinks of “wood chips as being the best soil additive available.”
“Wood chips are usually made by chipping entire trees—twigs, stems, branches, trunks and leaves. This results in a material composed of various sizes that is more resistant to compaction than bark mulch. The diversity of the material supports a wide range of soil microorganisms that are the key ingredient of a healthy soil. Wood chips slow the process of water evaporation, suppress weeds, maintain a stable soil temperature and prevent soil compaction.”
“Over time,” Mr. Chapman said, “wood chips break down, adding nutrients and organic matter to the soil. Better that wood chips be in the gardens than in the landfill!”
Leaves
He said they can be used in a vegetable garden between rows of plants for moisture retention and weed control, and they keep plants such as lettuce and spinach clean by preventing splashing mud caused by rain and irrigation. They would also work well as a mulch under tomato and pepper plants.
For Ellen Blanchard of Woods Hole, compost is the mainstay for her garden. She always has two compost piles going. One is for vegetable and kitchen scraps layered with leaves, garden trimmings, and deadheading, and the other is all the leaves from fall raking.
“We keep a two-gallon bucket for veggie scraps, coffee grounds, and egg shells under the kitchen sink. Every few days we empty the bucket onto our ongoing compost heap, and maybe once a week, pitchfork some leaves over it. Some folks like to keep track of the temperature inside their pile, to make sure it is ‘cooking’ nicely, and only turn it when the time is just right.
“I am not so particular about that, and turn it with a pitchfork when I feel like it… maybe more often than some. I find it very satisfying… especially when I see those zillions of happy wriggling worms breaking it down.
“In the summer, Ms. Blanchard said, “we usually start a new pile beside the decomposing one, and let the mature pile get ready for its move to the garden. Meanwhile, the huge pile of leaves on the other side of the yard is decomposing nicely. I don’t turn it as often as the veggie pile, but weather, and an occasional turn with the pitchfork, seem to do the trick.”
In the fall, when it’s time to rake again, she moves the mature vegetable compost and the decomposing leaf pile into the garden to sit for the winter and await springtime. Then, she starts a new leaf pile where the old one was.
In the spring, when the snow has melted, the compost piles she had moved to the garden are ready to be spread around wherever the soil needs amending, and mulching the flowerbeds and vegetables.
“The whole thing is a very rewarding process,” Ms. Blanchard said, “on this little teeny piece of the Earth where we live.”