Anemone is a common name applied to two distinct groups of organisms: marine sea anemones (predatory invertebrates related to coral and jellyfish) and terrestrial flowering plants known as windflowers (belonging to the genus Anemone). Both exhibit significant size variation depending on the specific species and the environment they inhabit.
Marine Anemones: Maximum Size Potential
Sea anemones exhibit an impressive size range, from small button-like species to massive organisms. The largest species, such as the Merten’s Carpet Anemone (Stichodactyla mertensii), can reach an oral disc diameter of over 3 feet (1 meter) in the wild. Other large varieties, like the Magnificent Anemone (Heteractis magnifica), commonly grow to between 1 and 2 feet in diameter, with some wild specimens approaching 3 feet.
The Sebae Anemone (Heteractis crispa) typically reaches a diameter between 12 and 30 inches. These large species require substantial space, a major consideration for hobbyists housing them in a home aquarium. The Giant Carpet Anemone (Stichodactyla gigantea) is another sizeable species, reaching about 20 inches across.
In contrast, other popular marine anemones are considerably smaller, making them better suited for smaller tanks. The Bubble Tip Anemone (Entacmaea quadricolor), a common host for clownfish, generally grows up to 1 foot (12 inches) in diameter in the wild, but often remains around 6 to 8 inches in captivity. The Rock Flower Anemone (Phymanthus crucifer) is one of the smallest species commonly kept, usually reaching only 1 to 4 inches in diameter in an aquarium setting, though wild examples have been documented up to 8 inches.
Factors Determining Anemone Growth and Dimensions
A marine anemone’s size is dynamic and influenced by its environment. These invertebrates host symbiotic algae called zooxanthellae, which use photosynthesis to provide a significant portion of the anemone’s nutritional needs. Consequently, light intensity and spectrum are major factors dictating size; if lighting is inadequate, the anemone may expand its oral disc to increase the surface area for light absorption.
Nutrient availability also drives growth, as anemones benefit from supplemental feeding of meaty foods like shrimp or fish. Anemones fed regularly grow faster and larger than those relying solely on photosynthesis, and frequent feeding can encourage asexual reproduction, or splitting. The presence of symbiotic clownfish impacts growth, as the fish provide nutrients and improve water circulation, leading to growth rates up to three times faster than in anemones kept in solitude.
Water flow is also important; moderate flow helps deliver food and oxygen while removing waste, but too much direct flow can stress the animal. Anemones may move around the tank to find an optimal location with suitable light and flow. Furthermore, anemones can shrink dramatically during periods of stress or starvation, demonstrating that size reflects current health and environmental conditions.
Terrestrial Anemones: Height and Spread of Garden Varieties
Terrestrial anemones, or windflowers, are flowering plants whose size is measured by height and lateral spread. The Japanese Anemone (Anemone hupehensis or A. × hybrida) typically grows to 2 to 4 feet (60–120 cm). This variety forms clumps with a similar spread, often naturalizing over time through underground rhizomes.
Certain cultivars, such as Anemone × hybrida ‘Honorine Jobert’, can reach heights of up to 4 to 5 feet, making them excellent additions for the back of a garden border. At the smaller end of the spectrum is the Wood Anemone (Anemone nemorosa), a low-growing species. This plant forms ground cover, reaching a height of only 6 to 10 inches (15–25 cm).
Its lateral spread is slow, increasing by only 1 to 2 inches per year via creeping rhizomes, making it a well-behaved choice for woodland gardens. The Poppy Anemone (Anemone coronaria) is an intermediate variety, generally growing to a height of 10 to 18 inches and spreading between 6 and 9 inches wide. These dimensions allow it to be used effectively in containers or along garden edges.