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Visit to the Aquatic Candy Store for
Acorus - Sweet Flag

by Dave Brigante, Oregon USA
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This unique family of marginal aquatic plants allows for many different fundamental uses while also lending itself to being versatile enough that creativity in design comes easily. The Acorus’ range in color can put it into a small pond as unifier or can bring out a backdrop in a large pond setting through its bright variegation. That being said one of its best uses is in a water bowl, as a focal point or ringing an edge of a miniature fairy pond. This family, often taken for granted in the aquatic plant kingdom, eventually finds its way into most well balanced pond designs due to its unrelenting availability, reliability and wide range of assorted sizes and colors. 

Most growers of Acorus generally think of the genus as having only two species. The first, Acorus calamus, from temperate and tropical Asia, may have become somewhat naturalized here in the US, but it is actually our own native sweet flag Acorus americanus that we see most frequently in the wild. In the trade, these are sometimes interchangeable and rarely sorted out, leading to nomenclature difficulties.

Neither of these species is promoted nearly as much as Acorus calamus ‘Variegatus’, variegated sweet flag. The other main species in the genus is Acorus gramineus, also known as Japanese sweet flag, native to temperate and tropical Asia. For convenience I will only refer to the two better known species (calamus and gramineus) to reduce confusion.

< A. gramineus

There are some marked differences between the two species. The A. calamus group loses its leaves each winter while A. gramineus does not. The A. calamus’ growth habit is more of a runner and the A. gramineus stays in a clump. A. calamus is limited to being either green or variegated, and A. gramineus has shades of yellow, white and green with some variegated varieties as well. Last, A. calamus grows to a height of 2.5'-3' (.8-1 m), much taller than A. gramineus that tops out at 12" (.3 m) and shrinks down to just 2-3" (5-8 cm) in its shortest form. Both are stunning in their own right. 

Above right - A. calamus 'Variegatus' in winter^>
Right - A. gramineus 'Odon' in winter >



All are called sweet flags for two reasons. A. calamus often looks just like blue flag iris when not in bloom and has been mistaken for iris in the wild. That is until the leaves are crushed or some of the smaller varieties get walked on and the sweet flag fragrance is released into the air. This sweetness of the roots and leaves was reportedly used to make candies, potpourri, natural insecticides, beer, and had many medicinal uses, too numerous for listing. Its availability in the wild became much more limited as it was integrated into the lives of the local tribes and early settlers.

The taller sweet flag (A. calamus) species is generally used as a filler plant to set off the more striking pond plants in a plan. It is very underused, mainly due to its lack of availability. Not having a significantly beautiful flower further reduces its overall appeal.

The sweet flag clan is certainly not known for its flowers. It’s all about the foliage when it comes to these little sweeties. In addressing the flowers' style, they are club-like in shape turning to a coffee brown as the summer wanes. Most go unnoticed, especially on the smaller varieties, not something to write home about.  

A. calamus ‘Variegatus’ >

Back to the common sweet flag. It is not considered a real eye catcher. It’s the variegated sibling A. calamus ‘Variegatus’, variegated sweet flag, that can easily hold its own in most waterways. If placed as a specimen plant or as a mass planting, this beauty demands attention.  

One aspect of this aquatic marginal that I really like is its new growth as spring comes along. As previously mentioned this species does lose its leaves in the winter, but what a sight it is as it makes its return. Not only is it vibrant green and white, but there is also a pink infusion of color that makes having it in close proximity a must.

As the growing season moves along, sharing space with this beacon can be very illuminating. The Colocasia genus, commonly known as elephant ears or taro, makes great companion plants for variegated sweet flag, especially 'Black Magic' taro. The dark maroon leaves contrast extremely well against the white and green sheen of the sweet flag leaves. I can also see blending some Papyrus family members into the mix. Using the tried and true umbrella palm (Cyperus alternifolius) is always a summer enhancing experience. You can add even more to the scene by injecting some purple hues such as powdery Thalia, also known as hardy Canna (Thalia dealbata), or some of the many purple water iris that are plentiful at most aquatic garden centers.  

Moving on to the A. gramineus collection, I need to mention that I will primarily describe the better known varieties that would most likely be found during a plant excursion, yet it should be noted that there are a few other more obscure specimens out and about that you may run across.  
The foundation plant of this species is of course the dark green and grassy looking Japanese sweet flag. It stays at about 12" (31 cm) tall and forms a 12"-15" (31-38 cm) clump if left to grow freely. A 1-2" (2-5 cm) water depth is all they really need to be happy. The most fun we have at the nursery is trying to distinguish it from A. gramineus ‘Licorice’ -- lots of sniffing and crumbling of the leaves to get to the real truth. It becomes pretty evident as that anise aroma shows itself.

A. gramineus ‘Licorice’
It truly is quite remarkable how similar they are besides that. A couple of other forms that are similar in stature to the Japanese sweet flag are A. gramineus ‘Ogon’ and A. gramineus ‘Variegatus’.  

The golden Japanese sweet flag (‘Ogon’) is striped with deep shades of yellow combined with a creamy white. This is a good one to mix with black mondo grass (Ophiopogon planiscapus nigrescens), (great aquatic but very slow), or Astilbes and Japanese primrose when it is used as a well-watered terrestrial.

A. gramineus ‘Ogon' >


The ‘Variegatus’ Japanese sweet flag has typical green and white variegation that may blend well with Lobelia ‘Queen Victoria’ or blue Medusa corkscrew rush (Juncus spiralis ‘Afro’). Both the golden and the variegated Acorus can add good foundation and depth to most pond edges.

< A. gramineus ‘Variegatus’ 

The last two of this clan are the smallest. The first, A. gramineus ‘Pusillus’, is a dwarf version of the common Japanese sweet flag, with dark green strap leaves. It only reaches a height of 5"-6" (13-15 cm) while remaining compact, not sprawling beyond those constraints laterally. That makes it very good for small ponds and water bowls.  

A. gramineus ‘Pusillus’ >

A. gramineus ‘Minimus Aureus’  
The second little gem, miniature golden Japanese sweet flag (A. gramineus ‘Minimus Aureus’), is something to behold. If ever there was a dwarf plant that works well in a table top water bowl or even in a small floating island, this is it. It only grows to a height of 2" (5 cm) and over time it will spread to maybe 3"-4" (8-10 cm). I’ve always thought that by combining these bright yellow bundles with carnivorous plants or with the dwarf corkscrew rushes, a perfect little world can be created. Add in a little fairy dust and who knows what might happen. These two mini sweet flags really prefer to be saturated to a depth of no more than ½" (1 cm) or to be kept constantly moist.  

Sometimes as aquatic plant lovers we find certain plant lines that can make our busy lives just a little bit easier. The Acorus family falls into that sphere. The care requirements are fairly simple. If the plants are given the correct water levels, trimmed back a bit before springtime, given a light environment somewhere between full sun and part shade (and don’t put them in USDA hardiness zone below 3 or above 11) you will be able to keep these living on the sweet side for a long time.

At the nursery we occasionally run into some minimal insect problems, mostly due to the fact that they are growing together with so many other genera. In most ponds with the natural defenses, it’s likely that all that could be needed is to sink them under the water for a couple of days. Besides the ease in caring for them, they are all propagated by division during the spring and summer, even into the fall, if they can be protected through the winter. They are exceptional plants, especially during the propagation process, when you feel like you are working in a candy store. 

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