Growing Acorus Gramineus ‘Variegatus’ Plants: Caring For Sweet Flag

As evident from its common names, acorus gramineus ‘variegatus’ [AK-or-us, gram-IN-ee-us, var-ee-GAY-tus] is a plant with a grassy appearance and is native to Japan, Korea, and East Asia.

A species of the family Acorus, the plant is seen growing in shallow water and wetlands in its native habitat.

Acorus Gramineus 'Variegatus' Plant aka (Sweet Flag)
Photo David J. Stang [CC BY-SA 4.0], via Wikimedia Commons
You may hear it called by its common name including:

  • Grassy-leaved Sweet Flag
  • Japanese Sweet Flag
  • Japanese Rush
  • Dwarf Sedge
  • Dwarf Sweet Flag
  • Golden Variegated Sweet Flag
  • Variegated Sweet Flag

Acorus Gramineus ‘Variegatus’ Care

Size & Growth

Dwarf Sweet Flag  is a compact, deciduous, water-loving rhizomatous perennial growing up to 11” – 12” inches in height.

The plant is often referred to as grass-leaf because it produces clumps of long and narrow green-colored leaf blades with creamy-yellow streaks looking like grass.

However, although it is grass-like it does not belong to the grass family.

The foliage of the Japanese rush plant spreads out like a fan as the plant grows and gives off a soft sweet fragrance when bruised or crushed.

The foliage color and intensity of variegation depend on light exposure.

The plant can take 2 to 5 years to reach the ultimate height.

Flowering and Fragrance

The plant produces small flower spikes near the tips of central stems from spring to early summer.

But, since they are the same color as the plant foliage, i.e., green, they do not stand out and hence, are insignificant.

Flowering season is followed by the production of tiny fleshy red-colored berries.

Light & Temperature

Acorus prefers full sun, but it also appreciates some light shade or partial shade in hot weather.

If you live in an area where summers are long and very hot, it is better to grow this plant at a site where it gets filtered sun or afternoon part shade.

However, make sure not to plant it in full shade as reduced light can slow down its growth.

Plant can tolerate temperatures as low as 39° degrees Fahrenheit (4° C).

United States hardiness zone 6 – 10 (USDA Zone).

Watering and Feeding

Acorus gramineus ‘variegatus’ is a moisture-loving plant growing best when it is submerged in water.

While it grows in very moist soils, it is not likely to flower unless it is at least partially submerged in water.

When grown in a pot, water the plant regularly and plentifully to make sure the potting mixture always remains thoroughly moist.

Place the pot in a shallow tray filled with water to maintain moisture levels.

An important thing to note here is the life of a grass-leaf sweet flag is reduced if it is exposed to water over 72° degrees Fahrenheit (22° C) for long periods.

Feed the plant with a standard liquid fertilizer once every two weeks during the spring and summer seasons.

Soil & Transplanting

Grass-leaf sweet flag can grow in a wide variety of soils but prefers wet soil they have to be fertile, wet or very moist, and poorly-drained.

Variegated Sweet Flag spreads by rhizomes, and hence need to be divided every few years to prevent congestion.

Transplant the plants in spring and use a soil-based potting mixture for best results.

Grooming and Maintenance

Acorus gramineus ‘variegatus’ is a low maintenance plant type growing without requiring much effort from your end apart from maintaining the moisture level.

Plants having spread too much should be pruned to tidy up the foliage.

Spring is the best time for pruning Japanese rush plant.

Its main bloom time is early summer.

Related Grass-like plant: Cyperus Alternifolius (Umbrella Papyrus)

How to Propagate Japanese Sweet Flag

Propagate grass-leaf sweet flag by clump divisions after every 3 to 4 years.

Divide the clumps with hands, ensuring there is at least one rhizome attached to every division, at the start of the growing season, i.e., early spring.

Plant the divisions in pots until they develop roots and let them establish properly before transplanting to permanent locations.

Dwarf Sweet Flag Pest or Diseases

Grass-leaf sweet flag plants remain free of pests and diseases while being deer resistant.

However, the leaves can get scorched due to lack of water, so make sure the soil is consistently wet or very moist to keep the plant healthy.

In hot locations with no air movement spider mites will attack.

Dwarf Sedge Uses

Japanese rush plants are a great plant for water gardens, rock gardens, and for edging alongside streams and ponds.

It also makes an excellent ground cover or foliage accent, provided the soil remains moist all the time.

It is also grown as an aquarium plant if you maintain water temperature below 72° degrees Fahrenheit (22° C).