Stratford H. Kay, Ph.D.
Aquatic Weed Management Specialist
North Carolina State University, Raleigh, NC 27695

The popularity of water gardening has increased dramatically in North Carolina and throughout the country during the past few years, particularly due to the advent of hobbyist magazines and the appearance of mail-order and on-line plant sales and propagation information. Water gardens now are major attractions in arboreta and botanical gardens nationwide, and backyard water gardens have become commonplace. Sales of equipment and plants for water gardens have nearly doubled annually over the past five years, and industry projections suggest that this rate of increase will continue for at least another five years. An attractive water garden is an aesthetic asset and even may be a financial asset in terms of increasing property values.

Closely related to water gardening is another aspect of ornamental landscaping often called "aquascaping". The aquascaper seeks to beautify the landscape by planting of a variety of interesting and colorful plants in what otherwise would be rather drab ponds and wetlands. The tightening of environmental regulations to require vegetated buffer zones to intercept nutrient runoff and retard soil erosion around new and existing ponds and wetlands, coupled with the desire to beautify these areas, has led to a significant increase of aquascaping activities on golf courses, in apartment and other residential complexes, on college and industrial campuses, and in many parks. Sales of plants for aquascaping are booming in North Carolina and elsewhere in the Southeast, and many of the nurseries producing aquatic and wetland plants are sidelining as landscape contractors for aquascape installation.

Lake restoration and mitigation activities more recently have drawn the attention of the public and of the aquatic and wetland nurseries. Sediment removal, aquatic weed management operations, and wetland creation and mitigation activities are becoming increasingly more common. Any activity which restructures the shoreline of a lake or reservoir, increases wetland habitat, or removes noxious weeds, provides new habitat suitable for colonization by vegetation. Quite often the colonizing vegetation is invasive in nature (e.g., dense stands of cattails, noxious water weeds such as hydrilla, smelly growths of filamentous algae, etc.) and creates problems unless proper management strategies are implemented. One approach to this situation has been to plant desirable species before the new habitat is colonized by the undesirable ones. In theory, these plants would colonize the available space and provide competition that will retard the establishment of undesirable species. Simultaneously, revegetation with desirable species would prevent shoreline erosion and be aesthetically appealing.

Aquatic and wetland plants for water gardens, aquascaping, and lake restoration until quite recently have been purchased largely from out-of-state nurseries, as few sources were available within North Carolina. This has presented several problems, including the introduction of species that are unsuited for their new environments and others that may become weeds. The increasing availability of plants from mail-order and on-line catalogs has only aggravated this situation.

The demand for water and wetland plants has spawned the growth of aquatic plant nurseries in a number of locations in North Carolina. These new nurseries, in turn, have obtained most of their stock from out-of-state sources. A few also have permits and are collecting locally. In some cases, the nursery stocks purchased from other nurseries as well as locally collected plants contain undesirable, invasive species such as hydrilla as contaminants. Occasionally a contaminant species looks interesting and ultimately becomes cultivated and sold by the industry. A number of undesirable species (e.g., giant salvinia) have been cultivated, sold, and distributed widely, either mistakenly or intentionally, under the under the wrong scientific and common names.

Most of the plants sold for water gardens and aquascaping, are not native to North Carolina or the United States. The great majority of these plants never become problems. However, a few have proven to be highly invasive (e.g., waterhyacinth and purple loosestrife) and have caused significant environmental damage through habitat destruction. These species crowd out more desirable native plants and may result in elimination of the types of habitat needed by aquatic invertebrates, fish, and wildlife. Their economic impact also may be devastating. Dense growths of invasive aquatic and wetland plants obstruct navigable waterways, restrict drainage, clog water intakes, degrade water quality, and interfere with fishing and recreation.

Preventing the introduction and spread of noxious aquatic weeds can save millions of dollars of public and private money annually which would be spent for economic losses and control activities. Just because a plant is interesting or has a pretty flower does not constitute justification for releasing it into the environment when it has a history of being invasive. Invasive species including giant salvinia and hydrilla (both Federal Noxious Weeds), creeping waterprimrose and purple loosestrife (NC Noxious Weeds), are not native to the United States and have entered either as contaminants among other plants or as intentional introductions. These designated federal and state noxious aquatic weeds are regulated under a combination of Federal Noxious Weed Laws, North Carolina Noxious Weed Laws, and the NC Aquatic Weed Act of 1991. The Aquatic Weed Act of 1991 specifically empowers the North Carolina Department of Agriculture and Consumer Services and the Department of Environment and Natural Resources jointly with the authority to regulate the importation, possession, propagation, distribution, and sale of illegal aquatic plants. Several other non-native species including Brazilian elodea and parrotfeather, are highly invasive but currently are not regulated in North Carolina. Even some native species including cattails, waterlily, lotus, duckweed, and mosquito fern, may become invasive if planted or allowed to escape into ponds, lakes, streams, and wetlands. One tiny, native, free-floating plant, watermeal, is a common contaminant of aquatic and wetland nursery stock and is extremely invasive and difficult to control if allowed to escape into ponds. It has become one of the four or five most common and troublesome weeds in irrigation ponds throughout North Carolina and the Southeast.

All of the plants mentioned above have one very important characteristic in common: they are highly invasive weeds when allowed to become established in ponds, lakes, and wetlands. With the exception of hydrilla and watermeal, all (including giant salvinia, illegally) are being sold widely for water gardens and aquascaping. The free-floating species ( waterhyacinth, giant salvinia, mosquito fern, duckweed, watermeal) are easily moved from site to site by water currents, birds and mammals (including people) to become problems. The underwater plants ( parrotfeather, Brazilian elodea, and hydrilla) will completely overtake shallow ponds, lake margins, drainage ditches, and canals. Hydrilla and Brazilian elodea may form dense surface mats in water 10 feet or more in depth. Is this what YOU want in your ponds and lakes? And how about the monetary investment that went into buying and planting these plants? And how much are you willing to spend to get rid of those plants which become weedy?

Careful consideration of the nature of the plants you plant to put into a water garden, aquascape, or wetland can reduce the likelihood of inadvertently creating an eyesore or major weed management problem. Most of the ponds and other areas that are to be "beautified" with plantings of aquatic and wetland vegetation are very shallow (many are less than three feet deep) and receive runoff from highly managed turf. The combination of clear, shallow water and substantial nutrients in the runoff water create the very conditions most conducive to the rampant growth of filamentous algae and invasive plants. A wise approach is to select native vegetation whenever available and to plant only those species which usually are not invasive. Plants such as blue-flag iris, pickerelweed, horsetail or scouring rush, soft rush, several species of spikerushes, lizard's tail, arrow arum, and arrowhead are native, have attractive foliage and/or flowers, are easily established and well adapted to the North Carolina environment, and usually do not become serious problems (i.e., they are easily managed). They all are perennial, overwinter nicely, and are available from in-state aquatic and wetland nurseries.

The best assurance of having attractive, trouble-free water gardens, aquascapes, and wetland plantings is careful plant selection. Educate yourself about the nature of aquatic and wetland plants, and know what you want before you purchase. Beware of salesmen who seem too eager to sell you large numbers of expensive, pretty plants and who assure you that they are not invasive and will never become troublesome. Even when purchasing native plants from local sources, be sure your plants are free of unwanted contaminants. This means that you must examine the plants you buy very carefully before planting. Visit the nursery and look at the plants they have for sale and whether or not there are other plants mixed in with them. If you should find contaminants such as duckweed, watermeal, or others, do not accept the plants. Also be sure that your source of plants is a state certified nursery or dealership. When planting water lilies, lotus, and cattails, use only containerized plants; this reduces the likelihood that they will spread into areas where they are unwanted. Whenever you feel that you may have a problem, consult a qualified specialist for assistance. Further information may be found at the NCSU Aquatic Weed Management website at:


This site also has links to on-line publications and other websites related to aquatic plants and their management. For additional photos of aquatic and wetland plants, see the University of Florida's website: http://aquat1.ifas.ufl.edu/photos.html.

web page design: Judith A. Goodman