Acorus: Japanese Sweet Flag
Acorus are grown primarily for their bright, cheery evergreen foliage that is clumping and grass-like in character.
Plant care & info
Genus: Acorus
Family: Acoraceae
Common Name: Japanese sweet flag, sweet flag, flagroot, sweet calamus
A sedge-like genus of two evergreen perennial species (A. gramineus and A. calamus) from temperate East Asia and southeastern United States.
Acorus species are tough and easily grown. Because they’re native to pond margins, they prefer fertile, acidic soil that is constantly moist. They also resent drying out and will produce brown tips and burnt foliage. They tolerate sun to part shade conditions.
They do not require much maintenance, but will benefit from division every few years when the center of the clumps become sparse. At this point, divide the rhizomes and replant them. Otherwise, maintenance includes cutting out dead or bad-looking foliage and keeping the plant moist.
Slug damage is just about all you can expect!
The plant’s flower spikes are largely inconspicuous on A. gramineus, while they are larger on A. calamus.
The leaves of A. gramineus are in flattened fans like those of irises, crowded along short rhizomes, while the leaves of A. calamus are taller. Both leaves and rhizomes of both species are sweet-scented and the stout, aromatic rhizomes of A. calamus contain compounds sometimes used in herbal medicines or perfume.
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Acorus Calamus
A. calamus is a perennial associated with wetlands throughout Eurasia and eastern North America with green iris-like leaves to 5 feet long and a narrow elliptical green spadix (a fleshy spike bearing small flowers) to 4 inches long.
This species spreads slowly by underground rhizomes and is evergreen throughout most of its range. A. calamus ‘Variegatus’ has cream and yellow variegated leaves.
A. calamus is a showy and reliable water plant suitable for water gardens in the Pacific Northwest. A. calamus ‘Argenteostriatus’ is a variegated variety of the native that provides a bright spot of color and structure to the water garden.
Acorus Gramineus
This species is a great addition to mixed containers for sun or shade. It adds a wonderful pop of color and stays compact. In addition, because it is evergreen, it can be used in containers for all seasons and is especially fun in winter when options for grasses are more limited. A. gramineus also adds color and consistency to the front of mixed plantings or simple modern plantings where it looks especially good planted en masse. This species can can be a fantastic ground cover between pavers in a location where adequate moisture is assured.
Native to Japan, this species has green, soft curved leaves up to 18 inches long. The flower spikes are about 3 inches long and emerge in spring and summer. Clumps can be up to 2 feet wide and are slow to grow. Varieties include the following:
- ‘Golden Pheasant’
- Chartreuse to golden colored foliage and grows between 12 to 14 inches tall.
- ‘Minimus Aureus’
- Bright yellow foliage with a fine texture and grows to 4 inches tall.
- ‘Ogon’
- Gold and green variegation and grows from 10-12 inches tall.
- ‘Variegatus’
- White and green variegation and grows from 8-12 inches tall.
- ‘Yodo-No-Yuki’
- Olive-green foliage with a light yellow edge and grows up to 12 inches tall.
- ‘Hakuro-nishiki’
- Yellow-green foliage and compact in nature.
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