The attractive, feathery fronds of parrot feather plants (Myriophyllum aquaticum) often encourage the water gardener to use it in a bed or border. The delicate appearance of growing parrot feather complements other foliage in your water feature or bog garden.
I. Appearance and Characteristics
Myriophyllum aquaticum is a flowering plant, a vascular dicot, commonly called parrot’s-feather and parrot feather watermilfoil.
Parrot feather is a perennial plant. Parrot feather gets its name from its feather-like leaves that are arranged around the stem in whorls of four to six. The emergent stems and leaves are the most distinctive trait of parrot feather, as they can grow up to a foot above the water surface and look almost like small fir trees. The woody emergent stems grow over 5 feet / 1.5m long and will extend to the bank and shore.
Attached to the parrot feather are pinkish-white flowers that extend approximately 1/16 inches long. As the water warms in the spring, parrot feather begins to flourish. Most plants flower in the spring; however, some also flower in the fall. Almost all plants of this species are female, in fact there are no male plants found outside of South America. Seeds are not produced in any North American plants. Parrot feather reproduces asexually. New plants grow from fragments of already rooted plants. The plant has whorls of feathery blue-green to waxy gray-green leaves deeply cut into many narrow lobes.
Kasselmann recently described a new variety, M. aquaticum var. santacatarinense, which distinguishes itself from the typical variety by its more stiff and robust habitus and pinnae that are fewer and broader.
Parrot feather is native to the Amazon River in South America, but it can now be found on every continent except Antarctica. It is thought that this plant was introduced to North America around the late 1800s. It was first discovered in the United States in the 1890s in Washington, D.C. Parrot’s feather typically grows in freshwater streams, ponds, lakes, rivers, and canals that have a high nutrient content. During the 20th century it colonized areas in South Africa, Japan, England, New Zealand, and Australia. As it prefers a warmer climate, it is chiefly found in the southern parts of the United States.
II. How to Grow and Care
Sunlight
Parrot’s feather grows fastest in full sun (6 to 8 hours of direct light per day), but it tolerates sites with only morning sun. The less sun it gets, the slower it grows and the less efficiently it improves water quality.
Temperature and Humidity
As a native of the Amazon, parrot’s feather is comfortable with heat and humidity during the growing season. It thrives in warm, summer temperatures ranging from 70 to 100 degrees F.
In cold-winter areas within its hardiness zones, parrot’s feather dies back to the rhizomes. Below zone 6, where the plant is treated as an annual, parrot’s feather should be removed after frost and discarded.
Soil and Water
Plant its delicate rhizomes in heavy loam in pond bottoms or water garden containers. It will quickly root and begin to spread. Its ability to root also makes parrot’s feather a good transitional plant for shorelines but you will have to manage its prolific spread.
Fertilizing
Parrot’s feather does not require any fertilization.
Planting Instructions
Plant parrot’s feather at water’s edge, in containers, or place them on the surface of a pond in late spring after all danger of frost has passed. Plant rhizomes in a medium-size water garden container filled with heavy garden soil or dig a hole large enough to accomodate the roots and rhizome in a sunny spot in soil that remains moist at all times (at the margins of waterways is best).
You can also bury the rhizomes in pea gravel at the bottom of a small pond as long as the submerged plant receives ample sunlight.
Pruning
During the growing season, cutting back parrot’s feather only appears to encourage the plant to grow more vigorously. Manage the number of floating plants by lifting out new plants and discarding them. After a hard frost, it should be pruned to the ground or water level so the dead foliage doesn’t decompose over winter.
Propagation
Since parrot’s feather grows so prolifically, chances are you’ll spend more time managing its growth rather than trying to create more plants. Parrot’s feather may reproduce through fragmentation, an asexual process where a piece of the plant breaks off and grows into a separate adult plant on its own. As a rhizomatous plant, parrot’s feather can also be propagated by dividing a rhizome into pieces that each have foliage and roots attached.
Only female plants are known to grow in North America so they will not produce seed.
Potting and Repotting
Growing a parrot’s feather in a container is the best way to manage its aggressive spread. Use a perforated plastic pot designed for water gardens. Plant the rhizomes in heavy loam soil—do not use potting mix. Place the pot in the water garden so that the plants float freely on the surface. You may submerge the plant entirely beneath water but ensure that it is still receiving adequate sunlight to maintain its effectiveness as a water purifier.
As the plant is an annual in most areas where it is legal to grow, it will not need to be repotted and can be discarded at the end of the growing season.
Pests and Diseases
Parrot’s feather is a relatively pest- and disease-free plant. Dieback is one of the few issues you might face if the plant is growing in-ground and the soil dries out completely. Note that dieback is normal after frost.
III. Uses and Benefits
Its fine, almost fernlike texture makes parrot’s feather a beautiful contrast to lotus, water lily, and other big-leaf water-garden plants. It grows equally well in ponds and container water gardens.
Plant parrot’s feather with papyrus; its upright growing habit looks good with a carpet of low-growing parrot’s feather at the base. Or place the parrot’s feather near the water lily’s big, flat pads and attractive blooms to contrast with the fine texture of parrot’s feather.
The plant is especially useful for improving water quality: It efficiently absorbs excess nutrients, ensuring water purity and helping reduce the growth of unsightly algae. Unfortunately, it’s also valued by mosquitoes, who like to lay eggs around the plant as it floats in shallow water.
IV. Cleanup efforts
Herbicides have not been found very useful in controlling its growth, partly because the plant has a waxy cuticle that seals out the poison. Cutting and chopping can actually promote the plant’s spread. In the U.S. states of Alabama, Connecticut, Massachusetts, Maine, Vermont, and Washington, parrot feather is a declared noxious weed and is therefore banned from sale.
The two main solutions to manage this aquatic nuisance is physically removing the plant and or using herbicides.
The physical aspects of removal are such acts of cutting, harvesting, and rotovation (underwater rototilling). These methods see best results only when the extent of the infestation has taken over all available niches. Best results are seen this way due to the availability of space as compared to rapid growth. Using physical control methods while the plant is still invading will tend to enhance its rate of spread.
Another method of controlling Parrots feather is by the usage of herbicides. The herbicides are effective to the plant part exposed above water. The plant parts beneath the water never come fully into contact with the herbicides and are therefore washed away. Herbicides are most effective when applied to young growing plants. They should be applied repeatedly to show maximum results. M. aquaticum is more difficult to control with herbicides than other aquatic species. The leaves are protected by a thick waxy coating, and in order for herbicides to penetrate the leaves, surfactants must be added; however, herbicides may impact non-target native plants or animals.
In the United Kingdom, this plant is now classed as an invasive species and is one of five introduced aquatic plants that were banned from sale from April 2014. This is the first ban of its kind in the country.
In Europe, parrot feather has been included in the list of Invasive Alien Species of Union concern (the Union list) since 2016. This implies that this species cannot be imported, cultivated, transported, commercialized, planted, or intentionally released into the environment in the whole of the European Union.