Acorus
( ACK - or - us )
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At-A-Glance InformationAcorus, also known as Sweet Flag or Calamus, is a genus of perennial plants that needs ample water and light shade in the hottest climates but can take full sun elsewhere. These plants are native to North America, Asia, and Europe. They can grow with their roots in either water or soil, and look like clumps or tufts of grass. Plants are handsome when used in borders, at edges of pools, in shallow water, or in containers that are kept wet, and are commonly planted in groups. They also do well as foundation plants, in rock gardens, rain gardens, as edgings or groundcovers, and can even do well in containers. Take care when planting these grasses in the landscape, as there is some evidence that roots and other plant parts from some species may cause toxic reactions in pets and humans if ingested.
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Acorus Species and Varietals
The genus Acorus is the type genus member of the plant family Acoraceae, and includes just three species, though there is a good deal of debate concerning the classification of the species in the genus. The common name 'Sweetgrass' refers to the sweet scent of leaves when they are crushed. The best growing zones for Acorus vary by species, generally ranging between USDA growing zones 3-11; for more information, see the descriptions below. To find your zone, click here: Zone Map.
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Acorus americanus (American Sweet Flag, Belle Angelique) This wetland plant is native to the United States and Canada, and produces tufts of bright green grassy foliage. Leaves have a citrusy, spicy quality that makes it great for flavoring beer. Fertilized flowers will produce a berry that has jelly inside. This species does well in USDA hardiness zones 3-6. |
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Acorus calamus (Common Sweet Flag, Sway, Muskrat Root, Beewort, Bitter Pepper Root, Calamus Root, Flag Root, Gladdon, Myrtle Flag, Myrtle Grass, Myrtle Root, Myrtle Sedge, Pine Root, Sea Sedge, Sweet Cane, Sweet Cinnamon, Sweet Grass, Sweet Myrtle, Sweet Root, Sweet Rush, Sweet Sedge, Wada Kaha) Grows best in USDA hardiness zones 4-11 or Sunset zones 2-10 and 14-24. Leaves form in an upright clump about 2 feet wide. Foliage is sweetly fragrant when bruised or crushed, and plants will die back in winter but return in springtime. 'Variegatus' is a popular variety that has white-bordered leaves. Grows from rhizome. |
Acorus gramineus (Japanese Sweet Flag, Grassy-Leaved Sweet Flag, Slender Sweet Flag)
This species grows best in Sunset zones 3b-10 and 14-24 or USDA growing zones 4-10. It is native to Japan, China, Korea, India, Thailand, Myanmar and the Philippines and develops fans of semi-evergreen leaves rising from the ends of rhizomes. The specific epithet gramineus means grass in Latin. Varieties are listed and described below.
This species grows best in Sunset zones 3b-10 and 14-24 or USDA growing zones 4-10. It is native to Japan, China, Korea, India, Thailand, Myanmar and the Philippines and develops fans of semi-evergreen leaves rising from the ends of rhizomes. The specific epithet gramineus means grass in Latin. Varieties are listed and described below.
'Licorice'
Has a licorice scent and flavor. |
'Minimus Aureus'
Dwarf varietal that forms a beautiful mat of bright green and gold. |
'Oborozuki'
With green leaves that have central golden yellow stripes. |
'Ogon'
Narrow, arching golden-yellow leaves. |
'Pusillus'
3-5 inches tall, spreads slowly and is useful for planting between stepping stones. |
'Variegatus'
With leaves striped with white. |
Caring for Acorus
Acorus plants are typically purchased as specimens or bare-roots from a reputable nursery or other plant seller. Choose a spot in the landscape that has formal irrigation or is close to a water source. They do well in full sun to partial shade; ideally, they should be getting between 6 and 8 hours of sun each day for best color and growth, but do appreciate some late afternoon shade, especially in warmer climates. Space Acorus between 8 and 12 inches apart for best coverage and airflow. These plants will spread over time to form colonies via underground rhizome roots, eventually filling in any gaps in planting space. Ensure that soil is well-draining, rich in nutrients, and has a pH of between 5.5 and 6.5 (acidic). If local soils are particularly poor in nutrients or do not drain well, make sure to amend the planting area with plenty of organic compost before installing. Apply a layer of mulch around the planting area to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention. Water new plantings regularly as they establish a strong root system in their new home. At maturity, they appreciate consistent, regular waterings and even grow well in boggy or water-adjacent situations.
Fertilize yearly in early springtime with an application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. These plants are not heavy feeders, and this should be sufficient to provide the necessary nutrients for the active growing and flowering seasons. Prune off dead, damaged, diseased, or scorched leaves as necessary to improve the appearance of the plant. Every few years, check the growing area where Acorus is planted, and determine whether they need to be divided. After some time, Acorus will develop a bit of a central 'bald spot', and this is when they should be divided and replanted for both aesthetics and plant health. Acorus plants can live for many years, even decades, in the garden.
Harvesting Acorus
Certain species of Acorus, such as Acorus americanus, Acorus calamus, and other North American species, are edible. Before attempting to prepare or consume any Acorus plant, make absolute sure that it is an edible species; there are some species in the genus that are toxic if ingested. Various parts of the plant, including the rhizome (root), young stems, and flowers can be eaten raw or cooked. Young stems can be added to salads, and have a lemony, sweet flavor that is sometimes compared to vanilla. They can be used to flavor custards or other desserts, as well. Flowers can be added to salads or used as a garnish. Roots can be peeled and eaten raw, but can also be roasted as a vegetable, candied, or dried and powdered. It has a taste similar to ginger, cinnamon, or nutmeg when dried and can be used as a substitute for these flavorings.
Disclaimer: Information contained on this website is strictly and categorically intended as a reference to be used in conjunction with experts in your area. Foraging and consumption of plant parts should never begin without the guidance and approval of a local plant specialist. The providers of this website accept no liability for the use or misuse of information contained in this website.
Fertilize yearly in early springtime with an application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. These plants are not heavy feeders, and this should be sufficient to provide the necessary nutrients for the active growing and flowering seasons. Prune off dead, damaged, diseased, or scorched leaves as necessary to improve the appearance of the plant. Every few years, check the growing area where Acorus is planted, and determine whether they need to be divided. After some time, Acorus will develop a bit of a central 'bald spot', and this is when they should be divided and replanted for both aesthetics and plant health. Acorus plants can live for many years, even decades, in the garden.
Harvesting Acorus
Certain species of Acorus, such as Acorus americanus, Acorus calamus, and other North American species, are edible. Before attempting to prepare or consume any Acorus plant, make absolute sure that it is an edible species; there are some species in the genus that are toxic if ingested. Various parts of the plant, including the rhizome (root), young stems, and flowers can be eaten raw or cooked. Young stems can be added to salads, and have a lemony, sweet flavor that is sometimes compared to vanilla. They can be used to flavor custards or other desserts, as well. Flowers can be added to salads or used as a garnish. Roots can be peeled and eaten raw, but can also be roasted as a vegetable, candied, or dried and powdered. It has a taste similar to ginger, cinnamon, or nutmeg when dried and can be used as a substitute for these flavorings.
Disclaimer: Information contained on this website is strictly and categorically intended as a reference to be used in conjunction with experts in your area. Foraging and consumption of plant parts should never begin without the guidance and approval of a local plant specialist. The providers of this website accept no liability for the use or misuse of information contained in this website.
Propagation
Acorus plants spread via underground rhizomatous roots, and the best way to propagate them is by dividing these roots after a few years' time. This process is necessary even if the goal is not to propagate the plants; dividing Acorus will ensure the health of plants as well. This type of propagation is relatively simple; you will need a clean shovel, mulch, fresh soil (any kind will do, though it does need to be well-draining), compost, and pots (these are only necessary if you will be saving divided plants for transporting elsewhere). Division is best done in spring or fall (after the plant has entered dormancy and been cut to the ground, but before it has begun its new spring growth), and needs to be done every four to five years regardless of whether you have the goal of propagating the plants. To propagate by division, follow these steps:
- Gather your materials. Using a shovel, dig up your existing plant. Start from the outside and work your way in to avoid damaging the rhizome roots. Once you have worked it up out of the ground, lay it out.
- Start to tease apart the roots with your fingers. Once the roots are untangled, separate your plant into segments, ensuring that each one has at least one thick section.
- Prepare your pot(s) or new planting site(s) with amended, well-draining soil. You can either bring in new soil or simply amend your existing soil with compost to complete this task. Then, plant your divided rhizomes about an inch under the soil surface and water thoroughly.
- Apply a thick layer of mulch over the new planting to protect it from cold weather as it acclimates to its new home. Water regularly as it establishes a strong root system.
Acorus flowers fade to reveal their seeds. Each pyramid-shaped capsule contains 2-3 seeds.
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Acorus seeds are grey-brown to brown and tapered towards one end.
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Problems and Pests
Acorus plants are generally pest and disease resistant, though they can infrequently have issues with the following:
- Slugs and Snails
- Aphids
- Mealybugs
- Scorching
Gallery
The little foliage tufts provided by Acorus contrast well in this bed against Japanese Blood Grass.
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Here, Acorus is planted amongst blue sedge and other low-growing plants.
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Use Sweet Flag in between stepping stones to soften hard edges.
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Here, Flag is planted as a contrasting strip to border a planting bed.
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Acorus can make a great groundcover as long as it gets enough water to perform well.
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Use Flag in mixed beds to add a different color and foliage texture.
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Acorus naturally grows near bodies of water, and appreciates wet feet.
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Some leaf margins on Acorus plants are wavy.
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This tropical walkway is edged with beds filled with Acorus, Calathea, Cordyline, and Bird's Nest Ferns.
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Videos
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Learn about these grassy landscape plants.
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All about Acorus, or Sweet Flag, plants.
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Resources
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Page 133, Acorus
