Rose Treat turns 100 on Sunday. At 99, she is genial, relaxed and aware, if a bit hard of hearing. Though she uses a walker to get around, she is energetic and excited to share. She stands no more than five feet tall, and yet the strength of her character fills the room. She is without question an Island treasure. Her history is long and as full of life and variety as the sea by which she lives.

Rose Ehrenfreund was born in 1908 in Marisch Ostrava, Czechoslovakia. She came to America at the age of 14 months. “My family were innocent people,” she says. “When we first arrived, a man came up to us and said he could get us a better exchange rate on our money and so my parents gave them every last cent. He never came back with the money. It was a con. But even years later, my mother wondered about that man. She worried that something bad had happened to him, that he had fallen in the water or something. She was sad that she never saw him again.”

Without a penny to their name, the Ehrenfreunds faced becoming wards of the state and immediate deportation at the immigration office. At first, the two men working behind the counter flatly refused them entrance to the United States, which was especially tragic considering that Mrs. Treat’s father had sold off their home and his grocery store before coming to America. Despite much pleading, one of the immigration officers began to process the young family’s deportation. Meanwhile, 14-month-old Rose began to flirt with the other officer, waving her hands about and babbling. The man found himself unable to turn this adorable child away from a life in America. “Oh, let ‘em in,” he said to his coworker. And so the infant Rose became an American.

It is safe to say that unnamed bureaucrat made a fortuitous decision — Rose Treat is no wastrel. She grew up in New York and graduated from Columbia University. She became a registered nurse in Westchester county. But it wasn’t until after she left that career behind that she began to make what would become her most interesting contribution to society: the collection, identification and mounting of over 350 types of seaweed, all gathered from Vineyard waters. “I did this out of my own curiosity. I didn’t realize, at first, the importance of my work, but it turns out that it’s priceless,” she says.

Five years ago, she donated the entire collection to the Polly Hill Arboretum, which in turn inspired the creation of an herbarium there. The collection is kept safe in a pressurized environment to prevent decay. “A thousand years from now, if the world is still here, those mountings will be there and of great use to the scientific world,” says Mrs. Treat, wearing an expression of solemn pride.

Her interest in seaweed does not stop at taxonomy, however. While mounting samples, she discovered that she could manipulate the wet strands of algae into lines and shapes by pushing at them with a toothpick. The forms became images of birds, naked women, grinning cats and more. Mrs. Treat is not the only practitioner of seaweed art in the world, but her work is unique for its whimsy and grace. It has been shown at the Woods Hole Oceanographic Institution, Barnard College, Harvard University and the Martha’s Vineyard Historical Society, as well as in various private galleries throughout New England and New York. Her work can also be found at the Smithsonian’s Ocean Planet Exhibit in the Australian National Maritime Museum.

Seaweed is not Mrs. Treat’s first natural obsession. Before coming to the Vineyard, she and her late husband, mystery writer Lawrence Treat, lived in a wooded part of New York state. There, Mrs. Treat became an amateur mycologist, teaching herself about the mushrooms that grew in the forest around her home. She used to lead mushroom tours on Island, but stopped abruptly 12 years ago. “My husband and I came back from one of the tours and found that we were full of ticks. A mushroom walk is not worth getting sick for the rest of your life,” she says.

The attitude that ended those tours is a part of Mrs. Treat’s twofold secret to longevity, which is being published as a Gazette exclusive. The first part is obvious: Take care of your body. “Nature gave you a good thing. Don’t get into smoking and drugs and other crazy things. Be a good driver. Don’t endanger your life,” she says.

The second is inspiring. “Be aware of your surroundings. I’ve always been interested in my environment; it keeps you busy.” Indeed, Mrs. Treat’s long life has been marked by an acute fascination with the natural world and its endless parade of wonders, many of which can be found washed up on Vineyard shores.

Asked to name the greatest change she has seen in her century of life, Mrs. Treat recalls one morning when she was 12 years old, her mother took her with her brother to a suffragette parade in New York city. “The men on the sidewalk were standing there, making fun and spitting at the women as the marched, saying ‘Imagine, women voting!’ Well, we almost had a woman president coming up. That’s the greatest change that I’ve seen.”

Although she has had no formal training in phycology (seaweed science), Mrs. Treat is a true naturalist. She sees herself within the context of the Earth’s history, as opposed to the history of mankind. She speaks of glaciers leaving the rocks that make up our Island as one might speak of an old friend leaving a plate of cookies behind after a visit. A large glass table in her living room supports a random collection of sandy treasures: shells of all sizes, horseshoe crab tails, salt worn bits of brick and tile and a great number of stones. She seems to know each item intimately, her age-spotted hands moving through them with the dexterity of a much younger woman, the excitement in her voice clear and contagious as she extols the virtues of each scrap of seaside.

The seaweed that she has been collecting, cataloging and making art with for over 50 years is ubiquitous within the walls of her cozy Sengegentacket home. The birds, nudes and other creatures she has carefully nudged into being on paper share her views of the pond and her daily routine.

“I wake up in the morning, and the first thing I do is feel myself, and say ‘I’m still me!’” she says, smiling broadly. She stays busy with a large pile of unlabeled, unsorted seaweed mountings, which are categorized and then carefully placed into a purple binder. “I want to finish this before I die,” she says calmly, gesturing at the neat stack of mountings. “I want to finish what I started; I don’t want to leave a mess.” She reached to pick up a particularly beautiful sample of algal filigree. “Now isn’t that nature gorgeous?”

Please join the Island community in honoring Rose Treat on her 100th birthday this Sunday, Dec. 7 at the Agricultural Hall in West Tisbury from 3 to 5:30 p.m. The event is potluck, with music provided by the Vineyard Classic Brass Band.