Armoracia lacustris - (Gray) Al-Shehbaz & Bates
Synonym(s): Armoracia aquatica (Eat.) Weig. ;Neobeckia aquatica (Eat.) Greene ;Rorippa aquatica (Eat.) Palmer & Steyermark
Taxonomic Status: Accepted
Related ITIS Name(s): Neobeckia aquatica (Eat.) Greene (TSN 508081)
Unique Identifier: ELEMENT_GLOBAL.2.150383
Element Code: PDBRA07010
Informal Taxonomy: Plants, Vascular - Flowering Plants - Mustard Family
Kingdom Phylum Class Order Family Genus
Plantae Anthophyta Dicotyledoneae Capparales Brassicaceae Armoracia
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Concept Reference
Concept Reference: Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
Concept Reference Code: B94KAR01HQUS
Name Used in Concept Reference: Armoracia lacustris
Taxonomic Comments: Les (Aquatic Botany, 1994) showed that this taxon deserves segregation to the distinct, monotypic genus, Neobeckia, in which case its correct name is Neobeckia aquatica. Kartesz (1999) follows this treatment. As formerly treated in the genus Armoracia, A. lacustris would be the correct [older] name for the plant, although it has widely been known as A. aquatica. Previously placed in several other genera (Rorippa, Radicula, etc.).
Conservation Status

NatureServe Status

Global Status: G4?
Global Status Last Reviewed: 10Feb1994
Global Status Last Changed: 25Nov1986
Rounded Global Status: G4 - Apparently Secure
Reasons: Widespread, but apparently rare to uncommon throughout its range. The status of this species is poorly known in several southeastern States. It probably has been undercollected because it grows in wetlands, it flowers in early spring when water temperatures are cold, and it is usually observed and collected only when flowering (which does not occur every year). Seed production is poor at many sites. Exotic species threaten many sites. Confirmation of increasing threats may justify a G3 rank.
Nation: United States
National Status: N4?
Nation: Canada
National Status: N3? (11Apr2016)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Alabama (S1), Arkansas (SNR), Florida (SNR), Georgia (S1?), Illinois (S3), Indiana (S1), Iowa (SH), Kansas (S1), Kentucky (S1S2), Louisiana (SNR), Maine (SH), Maryland (S1), Massachusetts (SNR), Michigan (S2), Minnesota (SNR), Mississippi (S1), Missouri (S2), New Jersey (SH), New York (S2), Ohio (S2), Oklahoma (S1), Pennsylvania (SU), South Carolina (SNR), Tennessee (S2), Texas (S1), Vermont (S1), Virginia (SH), Wisconsin (S1)
Canada Ontario (S3?), Quebec (S1)

Other Statuses

NatureServe Global Conservation Status Factors

Range Extent Comments: Armoracia lacustris is found throughout central and eastern United States and southeastern Canada in a variety of aquatic habitats. This species reaches its northern range limit in Quebec and Ontario, Canada, extending southward through Michigan, Indiana, Ohio, Vermont, New York, Maryland, Virginia, Kentucky, Tennessee, and South Carolina to Florida, Georgia, Alabama, Mississippi, and Louisiana and westward to Texas, Oklahoma, Missouri, Illinois, and Wisconsin. Historically, populations also existed in Iowa and New Jersey. It is considered an introduced perennial in Oklahoma (Butler 1993).

Number of Occurrences: 21 - 80
Number of Occurrences Comments: ----(PENSKAR, WHITE): Approximately 50-100 occurrences reported in eastern North America, although many records are considered historical and the status of many populations is not known. Ohio - recently rediscovered along the St. Mary's River, one EO consisting of several thousand plants; Indiana - two extant EO's; Vermont - seven EO's, some of moderate to large size; Tennessee - 30 EO's, containing a few to up to several thousand plants; Kentucky - 14 EO's, with several moderate to large populations; Missouri - five EO's, three of which are extant; Virginia - known only from historical records; Quebec - number of extant EO's not known. ----(OSTLIE): Approximately 40 post-1970 occurrences are recorded in the Heritage system from eastern North America: Ohio (9 post-1970 occurrences); Indiana (2 post-1970); Vermont (3 post-1970); Tennessee (9 post-1970); Kentucky (9 post-1970); Missouri (3 post-1970); Mississippi (5 post-1970). The species has been extirpated from several states. Other states within the range are not tracking the species, but it is considered uncommon in all of them.

Population Size Comments: Most extant populations appear to be small; Vermont, Tennessee, Kentucky, and Ohio report populations comprised of hundreds to thousands of plants, whereas several other states report populations consisting of relatively few plants (approximately 100-150 plants or fewer). Although thousands of plants are noted for some occurrences, the number of genetic individuals in a population is difficult to estimate, owing to poor viable seed production and the ability to disperse via the disarticulation of leaf and stem fragments. (Nov94: Reportedly abundant in Louisiana also.)

Overall Threat Impact Comments: Development of habitat is one of the largest threats to Armoracia lacustris. Drainage or filling of wetland habitat for agriculture, development projects, roads, walkways, homes, and other shoreline changes is a serious problem through the range of the species (Pyne 1994, Anglin 1993, Dobberpuhl 1992, Homoya 1992, Kentucky Natural Heritage Program 1992, McCormac 1992, McCormac 1992, McCormac 1992, Mississippi Natural Heritage Program 1992, Popp 1992, Smith 1992, Young 1992).

Alteration of habitat through stream channelization (Kentucky Natural Heritage Program 1992, McCormac 1992) is a significant threat. In Florida, the creation of impoundments (e.g., farm ponds) is a significant threat (Anglin 1993). Oil drilling operations may physically destroy habitat (Homoya 1992).

Any change in the hydrological regime of an area is a threat to the welfare of this species. Increased water levels may flood existing habitat, while decreased water levels will lead to the loss of suitable habitat (Ladd 1993, Richards 1993, Summers 1993, Penskar 1992).

The degradation of water quality due to organic and industrial pollution sources, chemical run-off from agricultural fields, siltation and potential oil spills is a significant threat (Ladd 1993, Summers 1993, Dobberpuhl 1992, Homoya 1992, Labrecque 1992, McCormac 1992, Mississippi Natural Heritage Program 1992, Smith 1992, Young 1992). An historic occurrence in New Jersey was possibly lost due to the application of herbicides used to control Myriophyllum spicatum. All of the aquatic plant species with dissected leaves that were once present in the treated lake are no longer present. These plant species included Bidens beckii, Myriophyllum sibiricum, Ranunculus aquatilla, R. longirostris, R. subrigidus, and others (Snyder 1993).

Spraying of pesticides, alteration of wetland habitat, and other maintenance activities have been cited as potential threats to occurrences located along highway rights-of-way (White 1993).

Other threats to A. lacustris include recreation pressures on habitats, shoreline grazing, and watering by livestock, and herbivory by beavers (and potentialy by other wildlife) (Snyder 1993, Tennessee Valley Authority Regional Heritage 1992, Vermont Natural Heritage Program 1992).

Myriophyllum spicatum (Eurasian watermilfoil), Rorripa amphibia (marsh cress), Trapa natans (water chestnut), and other invasive, exotic, aquatic plants are of concern, as they decrease habitat quality and reduce or eliminate populations (Dobberpuhl 1992, Labrecque 1992, Popp 1992b, Vermont Natural Heritage Program 1992).

Insects may pose a threat to populations by feeding on fruit capsules and destroying seeds (Homoya 1992). The degree to which this is a threat is not known.

Short-term Trend: Decline of <30% to relatively stable
Short-term Trend Comments: Trends in A. lacustris are not well-known. The species has likely suffered significant declines in the past due to disturbance and loss of habitat. It is uncertain whether these declines have continued in recent years.

Intrinsic Vulnerability Comments: At least moderately fragile, due to the vulnerability of this species' wetland habitats and the general trend of threats with regard to these habitats.

Other NatureServe Conservation Status Information

Global Range: Armoracia lacustris is found throughout central and eastern United States and southeastern Canada in a variety of aquatic habitats. This species reaches its northern range limit in Quebec and Ontario, Canada, extending southward through Michigan, Indiana, Ohio, Vermont, New York, Maryland, Virginia, Kentucky, Tennessee, and South Carolina to Florida, Georgia, Alabama, Mississippi, and Louisiana and westward to Texas, Oklahoma, Missouri, Illinois, and Wisconsin. Historically, populations also existed in Iowa and New Jersey. It is considered an introduced perennial in Oklahoma (Butler 1993).

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map

U.S. & Canada State/Province Distribution
United States AL, AR, FL, GA, IA, IL, IN, KS, KY, LA, MA, MD, ME, MI, MN, MO, MS, NJ, NY, OH, OK, PA, SC, TN, TX, VA, VT, WI
Canada ON, QC

Range Map
No map available.

U.S. Distribution by County Help
State County Name (FIPS Code)
AL Colbert (01033)*, Greene (01063)*, Lawrence (01079)*, Limestone (01083)*
GA Ben Hill (13017)*, Dougherty (13095)*, Telfair (13271)*, Wilcox (13315)*
IA Clinton (19045)*, Muscatine (19139)*, Scott (19163)*, Union (19175)*
IN Allen (18003)*, Cass (18017)*, Daviess (18027), Dearborn (18029), Gibson (18051), Knox (18083)*, Lagrange (18087), Lake (18089)*, Monroe (18105)*, Pulaski (18131)*, Spencer (18147)*, Starke (18149)*, Sullivan (18153)*, Vigo (18167)*, Wells (18179)*
KY Ballard (21007)*, Butler (21031), Fulton (21075), Livingston (21139)*, Lyon (21143), McCracken (21145)*, Trigg (21221), Union (21225)
MD Montgomery (24031)
MI Alpena (26007), Cheboygan (26031), Gratiot (26057)*, Ionia (26067)*, Iosco (26069)*, Luce (26095)*, Mackinac (26097)*, Macomb (26099)*, Marquette (26103)*, Mason (26105)*, Muskegon (26121)*, Presque Isle (26141)
MO Bollinger (29017), Butler (29023)*, Christian (29043), Dunklin (29069)*, Howell (29091), Jasper (29097)*, Laclede (29105), Lafayette (29107)*, Mississippi (29133), New Madrid (29143)*, Oregon (29149), Pemiscot (29155)*, Saline (29195)*, Stoddard (29207), Wayne (29223)
MS Clay (28025), Leflore (28083), Oktibbeha (28105), Quitman (28119), Washington (28151)
NJ Sussex (34037)*, Warren (34041)*
NY Cayuga (36011)*, Cortland (36023), Erie (36029)*, Essex (36031)*, Jefferson (36045), Niagara (36063), Oneida (36065)*, Onondaga (36067), Oswego (36075)*, Saratoga (36091)*, St. Lawrence (36089), Warren (36113), Washington (36115)
OH Auglaize (39011), Madison (39097), Mercer (39107), Paulding (39125), Van Wert (39161)
OK Delaware (40041), McCurtain (40089)*
TN Grundy (47061)*, Lake (47095), Lauderdale (47097), Montgomery (47125)*, Obion (47131), Stewart (47161)
TX Tyler (48457)*
VA Southampton (51175)*
VT Addison (50001), Chittenden (50007)*, Franklin (50011)*, Grand Isle (50013)
WI Adams (55001), Bayfield (55007), Marinette (55075)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
02 Hudson-Hoosic (02020003)+*, Middle Delaware-Musconetcong (02040105)+*, Chenango (02050102)+, Middle Potomac-Catoctin (02070008)+
03 Nottoway (03010201)+*, Lower Ocmulgee (03070104)+*, Ichawaynochaway (03130009)+*, Tibbee (03160104)+, Middle Tombigbee-Lubbub (03160106)+*
04 Beartrap-Nemadji (04010301)+, Dead-Kelsey (04020105)+*, Betsy-Chocolay (04020201)+*, Peshtigo (04030105)+, Menominee (04030108)+, Little Calumet-Galien (04040001)+*, St. Joseph (04050001)+, Maple (04050005)+*, Pere Marquette-White (04060101)+*, Muskegon (04060102)+*, Brevoort-Millecoquins (04060107)+*, Lone Lake-Ocqueoc (04070003)+*, Cheboygan (04070004)+, Black (04070005)+*, Thunder Bay (04070006)+, Au Sable (04070007)+*, Pine (04080202)+*, Clinton (04090003)+*, St. Joseph (04100003)+*, St. Marys (04100004)+, Upper Maumee (04100005)+, Niagara (04120104)+, Seneca (04140201)+*, Oneida (04140202)+*, Black (04150101)+*, Chaumont-Perch (04150102)+*, Upper St. Lawrence (04150301)+*, Indian (04150303)+, Grass (04150304)+, Raquette (04150305)+, Otter Creek (04150402)+, Lake Champlain (04150408)+
05 Upper Scioto (05060001)+, Middle Ohio-Laughery (05090203)+, Middle Green (05110003)+, Upper Wabash (05120101)+*, Middle Wabash-Deer (05120105)+*, Tippecanoe (05120106)+*, Middle Wabash-Busseron (05120111)+*, Lower Wabash (05120113)+, Lower White (05120202)+, Lower Cumberland (05130205)+, Lower Ohio-Little Pigeon (05140201)+*, Highland-Pigeon (05140202)+, Lower Ohio (05140206)+*
06 Wheeler Lake (06030002)+*, Upper Elk (06030003)+*, Pickwick Lake (06030005)+*, Kentucky Lake (06040005)+, Lower Tennessee (06040006)+*
07 Castle Rock (07070003)+, Lower Wapsipinicon (07080103)+*, Lower Cedar (07080206)+*, Kankakee (07120001)+*, Chicago (07120003)+*, Whitewater (07140107)+*
08 Lower Mississippi-Memphis (08010100)+, Obion (08010202)+, New Madrid-St. Johns (08020201)+, Upper St. Francis (08020202)+, Lower St. Francis (08020203)+, Little River Ditches (08020204)+, Coldwater (08030204)+, Big Sunflower (08030207)+
10 Nodaway (10240010)+*, Platte (10240012)+*, Upper Grand (10280101)+*, Thompson (10280102)+*, Upper Gasconade (10290201)+, Blackwater (10300104)+*
11 James (11010002)+, Upper Black (11010007)+*, Eleven Point (11010011)+, Spring (11070207)+*, Lower Neosho (11070209)+, Pecan-Waterhole (11140106)+*
12 Lower Neches (12020003)+*
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
Basic Description: Perennial aquatic herb with fibrous roots and lax, submersed or prostrate stems up to 3 ft long. Dimorphic leaves differ on the same plant depending on whether they are submerged or now: submersed leaves compound-pinnate, emergent leaves lanceolate, 3-7cm long, toothed. The dissected leaves fall off readily when mature and serve as vegetative propagules. Flowers are white.
Technical Description: Glabrous aquatic or subaquatic, commonly submersed, sometimes alternately submersed and emersed as water levels fluctuate, the leaves very variable in relation to whether submersed or emersed or to length of time submersed or emersed, thus often with alternating segments of stem with leaves differing markedly. Leaves submersed for long periods 1-3 pinnately dissected into numerous filiform segments; other leaves oblong to elliptic or lanceolate, varying from serrate to dentate to pinnatifid, mostly 3-7 cm long. Floral racemes of variable lengths to about 1.5 dm long, weak, often curved or bent. Sepals 3-4 mm long, elliptic to spatulate or obovate. Petals white, short-clawed, their blades oblong to obovate, 6-8 mm long. Fruiting stalks widely divergent, about 1 cm long; siliques 5-8 mm long, ellipsoid, apparently seldom maturing seeds; persistent style 2-4 mm long. Seeds in 2 rows in each locule (Godfrey and Wooten, 1981).
Diagnostic Characteristics: Aquatic habitat, white 4-petaled flowers, and its size (6 dm above water surface) distinguish it from any other plant. The alternate leaves will readily distinguish this species from Ceratophyllum, Megalodonta, and Myriophyllum. The presence of a central axis will distinguish the leaves from those of aquatic Ranunculus and Utricularia. Proserpinaca and some rare Myriophyllums have alternate leaves with a central axis, but in these the lateral segments of the leaf are not again divided as they are in this species (Voss, 1985).
Duration: ANNUAL
Reproduction Comments: Populations appear to reproduce principally through asexual reproduction via the dispersal and rooting of leaf propagules; each leaf serves as the dispersal unit, in addition to stem fragments. When leaves reach the proper substrate, rooting is initiated, resulting in the formation of new plant rosettes. Seed production and viability are reported to be rather low, which may account for the apparently poor ability of this species to colonize new watersheds.
Riverine Habitat(s): Pool, SPRING/SPRING BROOK
Habitat Comments: The primary habitat of this species includes areas surrounding rivers such as oxbows and forested floodplains, pools alongs rivers, quiet shallow water along lake margins or in the backwaters of slow-moving streams, muddy rocky shores of large ponds and lakes, marl ponds derieved from glacial kettle holes, inundated roadside sloughs with open water, cypress swamps, seasonal sloughs, and open water in marshes.

In Florida, A. lacustris is found at spring runs in the panhandle region of the state (west of the Apalachicola River) (Anglin 1993).

Armoracia lacustris is found in Illinois in swamps and quiet streams (Mohlenbrock 1975).

In Indiana, populations have been reported growing in floodplain oxbows along the Wabash River in sandy silt substrates and in small, rocky bottomed pools within an abandoned channel of a small stream. Associated plant species include Carex torta (bordering clear pools) and Cephalanthus occidentalis (Homoya 1992).

In Iowa, the species historically inhabited quiet water and muddy shores (Roosa, et al. 1989).

Occupied habitat in Kentucky includes inundated roadside sloughs with open water, muddy waters, cypress swamps, seasonal sloughs, open water surrounded by cypress, swampy woodland, roadside ditches, alluvial plains, oxbows, floodplains, slow water and open marshes. It has been collected from sites having elevations ranging from 87 to 113 m (Kentucky Natural Heritage Program 1992, Tennessee Valley Authority Regional Heritage 1992). The species appears to require open water with depths from 0.3 - 0.6 m that lacks competition from other plant species and has partial to open sunlight available. Associated plant species include Alisma subcordatum, Carex sp., Cypress sp., Iris fulva, Sagittaria graminea and Saururus cernuus (Kentucky Natural Heritage Program 1992, Tennessee Valley Authority Regional Heritage 1992).

In Louisiana, A. lacustris is found in bottomland forests and cypress lakes. Dominant tree species in these habitats include Carya aquatica, Gleditsia aquatica, Quercus nuttallii and Taxodium distichum (Larke 1993).

In Michigan, occupied habitat is comprised of quiet, shallow water along lake margins or in the backwaters of slow moving streams (particularly cold spring fed waters), where it commonly roots in organic or sandy substrates. It occurs with such associate plant species as Myriophyllum species, Nasturtium officinale and Spirodela polyrhiza (Michigan Natural Features Inventory 1992, Voss 1985).

Armoracia lacustris is found in Mississippi in calcareous soil in open areas which are subject to periodic flooding. It has also been found in delta bottomland hardwood forests (and adjacent roadside ditches) on sharkey clay soils (Mississippi Natural Heritage Program 1992, Tennessee Valley Authority Regional Heritage 1992).

In Missouri, habitat includes bald cypress swamps, other wooded swamps, sloughs, slow streams, springs, shallow or still water and muddy shores of rivers and ponds. Summers (1993) described populations growing in the gravel bed of slough depressions of a creek and in the bottoms of seasonal streams which run in the spring and dry up in summer. Often, these seasonal streams are located at the bases of bluffs. In addition, old beaver dams have been observed across some of the streambed habitats. Associated overstory plant species (reaching over populations from creek banks) include Acer saccharum, Carya cordiformis, Celtis tenuifolia, Cercis canadensis, Fraxinus americana, Juniperus virginiana, Platanus occidentalis, Quercus alba, Q. muehlenbergii and Ulmus americana. Other associate plant species include Alisma triviale, Amsonia illustris, Bidens frondosa, Boehmeria cylindrica, Ceratophyllum, Cyperus sp., Eleocharis sp., Elodea sp., Eupatorium coelestinum, Heteranthera spp., Ipomoea, lacunosa, Justicia americana, Lobelia cardinalis, Ludwigia palustris, Mentha sp., Mimulus alatus, Penthorum sedoides, Phyllanthus sp., Potamogeton spp., Ranunculus flabellaris, Samolus parviflorus, Sium suave, Utricularia gibba and Veronica sp. (Summers 1993, Summers 1993, Smith 1992, Steyermark 1963).

Two historic occurrences are known from the state of New Jersey. The habitat for these occurrences was in lakes located within the limestone belt (Snyder 1993).

Occupied habitat in New York is the muddy, rocky shores of large ponds and lakes, and marl ponds derived from glacial kettle holes. Associated plant species include Cardamine pensylvanica, Lindernia dubia, Polygonum leersia, Potamogeton spp., Sagittaria sp., Sparganium americanum and Trapa natans (Young 1992).

Populations of A. lacustris in Ohio have been found growing in wet soil of seasonally inundated, disassociated channels of the St. Mary's River, densely forested floodplains, forested oxbows, buttonbush swamps, low lying divides and river terraces. The semi open riparian woodlands where A. lacustris grows are dominated by Acer saccharinum and Fraxinus pennsylvanica. In the wettest areas of the habitat Cephalanthus occidentalis is always present. Other associated plant species include Carex crus corvi, C. lupulina, C. muskingumensis, C. tribuloides, Leersia lenticularis, L. oryzoides, Ludwigia palustris, Polygonum hydropiperoides, Proserpinaca palustris, Rorippa sessiliflora, Samolus floribundus and Saururus cernuus (McCormac 1992a, Ohio Natural Heritage Program 1992).

In Oklahoma, A. lacustris occurs in the eastern one quarter of the state (Taylor and Taylor 1991).

Armoracia lacustris habitat in Ontario includes the edges of lakes, small streams and brooks, where it grows in water to depths of three feet. Scirpus sp. is an associate plant species here (Labrecque 1992).

Herbarium specimen labels from Quebec state that this species grows in lakes, rivers and small brooks in 0.6-0.9 m of water within the southern portion of the province. Scirpus sp. is an associated plant species here (Gouvernement du Quebec Ministere de l'Environnement 1992, Labrecque 1992).

In Tennessee, occupied habitat is still, open water of natural lakes or sloughs; ponds, canals, ditches and swamps (Pyne 1994). Occurrences have been found at elevations ranging from 85 to 309 m, with most occurring at 85 m (Tennessee Valley Authority Regional Heritage 1992). Associated plant species include Ludwigia peploides ssp.glabrescens, Ranunculus flabellaris, Hydrocotyle ranunculoides, Justicia ovata, Polygonum lapathifolium, Polugonum spp., Alisma subcordatum, Carex decomposita (noted on the bases of Cypress trees in some areas), Cypress spp., Hottonia inflata, Sagittaria graminea, Salix sp., Sassafras albidum and Saururus sp. (Pyne 1994, Tennessee Department of Environment and Conservation 1992, Tennessee Valley Authority Regional Heritage 1992, Chester 1975).

The single historic occurrence in Texas was found in water and mud on the west side of a lake in Tyler county (Texas Natural Heritage Program 1993). No extant populations are known from the state.

Vermont habitats include lake floodplain forests (such as that at Lake Champlain) with fluctuating water levels (especially due to spring flooding). Armoracia lacustris has been collected from elevations ranging from 25 to 54 m within the state. This low floodplain forest habitat is dominated by Acer saccharinum and Populus deltoides, with plants often being found among logs and driftwood. Other populations have been reported from river, stream and creek floodplains, swamp forests, slow streams, ponds formed at the mouth of streams and muddy banks along railroad tracks. These habitats range from being dry to moist to inundated and are usually flat and open (Vermont Natural Heritage Program 1992).

The historic habitat for Armoracia lacustris in Virginia is known only from herbarium records, which indicated wet creek depressions of sandy, alluvial bottomlands (Ludwig 1992, Virginia Division of Natural Heritage 1992). No extant populations are known.

The habitat reported for one occurrence in Wisconsin is cold, clear, shallow water of a sandy bottomed stream flowing through a bog embayment along Lake Superior. The community types related to this species are cold, hard, slow streams and open bogs. Another occurrence was found in a small pool in an intermittent stream running through deciduous woods. When last seen in 1980, this occurrence was found in a nearly dry mid stream bed with algae (Dobberpuhl 1992).

Economic Attributes Not yet assessed
Management Summary
Stewardship Overview: Management for A. lacustris should include the protection of its habitat from agricultural activities, urbanization, construction, shoreline improvements and destructive recreational activities. High water quality should be maintained, which may be degraded by organic and industrial pollutants, chemical run-off, siltation, aquatic herbicides and oil spills. Additional threats include hydrological perturbations, competition from exotic plant species and excessive grazing. Habitats may require selective cutting of overstory vegetation in order to restore open canopies in shaded habitats. Monitoring needs include the determination of population status, trends, reproductive success and an assessment of habitat quality and threats. Surveys should be made to locate additional extant populations and to relocate historic occurrences. Research is needed to study reproductive and population biology of the species, characterize required habitat parameters, investigate plant response to lowering water levels, and determine the effects of competing aquatic plant species.
Restoration Potential: Armoracia lacustris may be easy to introduce into suitable habitats. Personal experiments by McCormac (1992a, 1992b) have shown that plants will grow from cauline leaf cuttings placed in potting soil. Factors affecting the survivorship of rosettes into maturity in natural systems is poorly understood. To date, no restoration efforts have ever been undertaken and successful reintroduction into the wild can only be speculated.
Preserve Selection & Design Considerations: Preserve designs should consider the problem of protecting wetland habitats that can be seriously degraded by indirect, hydrologically upgradient activities such as pollution and stream channelization. Protection of a portion of a watershed, river or lake may not be sufficient. Preserve designs should encompass habitat of sufficient extent such that population expansion and recolonization can occur.
Management Requirements: Management efforts must foremost protect the hydrological integrity of occupied habitats. These efforts include the prevention of stream channelization and maintenance of water quality by eliminating threats from agricultural siltation, chemical or oil contamination and other factors. Working with adjacent landowners within watersheds (e.g., forming management agreements) may be crucial to the long-term survival of occurrences (Larke 1993, Richards 1993, Dobberpuhl 1992, Homoya 1992, Kentucky Natural Heritage Program 1992, Labrecque 1992, Mississippi Natural Heritage Program 1992, Popp 1992a, Smith 1992, Young 1992).

Exotic species control efforts should be undertaken to reduce risks from Myriophyllum spicatum (Eurasian milfoil), Rorripa amphibia (marsh cress), Trapa natans (water chestnut) and other invasive, exotic aquatic plants. Care must be taken to ensure that eradication or control efforts do not negatively impact A. lacustris populations (Labrecque 1992).

Recreational activities should be curtailed if they are deemed to be detrimental to existing populations.

There is also an apparent need to implement selective timbering at sites with excessive shading. This will open up the canopy which has shaded populations and reduced their flowering and fruiting abilities (Larke 1993, Homoya 1992, Labrecque 1992, McCormac 1992, 1992).

Threats of grazing livestock along shorelines adjacent to known populations should be eliminated if possible (Vermont Natural Heritage Program 1992).

Monitoring Requirements: Monitoring requirements include surveying populations on a frequent basis to determine population levels and reproductive success, resurveying populations to see if they are still extant, inventorying locations which have not yet been searched and monitoring populations for threats (Homoya 1992, Kentucky Natural Heritage Program 1992, Labrecque 1992, Popp 1992, Smith 1992, Young 1992).

Management Programs: Although the problems effecting Armoracia lacustris have been identified, there has been little in the way of advancements to produce any form of management programs for this species. In some areas this species is benefitting from managers who are protecting high-quality aquatic natural features, which is being done for reasons other than to specifically protect the habitat for this plant (Smith 1992).

The forest plan of the Mark Twain National Forest (MO) contains a riparian amendment that should provide protection for the habitat of A. lacustris. In addition, state law in Missouri prohibits driving Off-Highway-Vehicles (OHV's) in stream channels, which may be habitat for this species (Richards 1993). Contact: Lynda Richards, Forest Ecologist, Mark Twain National Forest, USDA Forest Service, 401 Fairgrounds Road, Rolla, MO 65401. Telephone: (314) 364-4621.

Seeds were to be gathered in Vermont during the summer of 1992 for seed banking, in cooperation with the NEPCOP (New England Plant Conservation Program) (Popp 1992a). Contact: Bob Popp, Botanist, Vermont Natural Heritage Program, Agency of Natural Resources, Center Building, 103 S. Main Street, Waterbury, VT 05671-0501. Telephone: (802) 244-7331.

Monitoring Programs: There are no known monitoring programs in place for this species.
Management Research Programs: McCormac (1992a, 1992b) found that this plant will root readily in appropriate substrates, later producing rosettes. Cauline leaves were planted in potting soil and rosette growth was observed. There is a need to determine the percentage of the rosettes that survive and develop to maturity in natural systems, because it may provide useful information for restoration efforts (since reasons for reduced reproductive success are unknown). Contact: James McCormac, Monitoring and Research Section, Division of Natural Areas and Preserves, Ohio Department of Natural Resources, Fountain Square, Building F, Columbus, Ohio 43224. Telephone: (614) 265-6453.
Management Research Needs: There is a need for studying the reproduction and dispersal processes of this species. Populations tend to persist through vegetative reproduction. Flower, fruit and viable seed production are rare in A. lacustris. The causes for low flower, fruit and viable seed production is not known. Additionally, it is unclear how A. lacustris successfully disperses. Propagules are rarely transported during flood episodes (McCormac 1992).

Research that would provide detailed habitat characterization (emphasizing water quality, pH, sediment load and similar parameters) is needed (Dobberpuhl 1992). Without such information, it is impossible to design and implement meaningful management programs.

Additional research is needed to determine where the sites of highest quality are located across the range of the species. In addition, investigations into how competition from other submerged aquatic species effects A. lacustris would aid managers in implementing control efforts and deciding whether controls are needed (Dobberpuhl 1992).

Research efforts are also needed to study the rate of seed production and dispersal in the species. This research will answer questions about whether low rates of seed production exist throughout its range and if they might cause rarity (Dobberpuhl 1992). This study should also yield information toward a better understanding of the role that management activities can play in increasing seed viability.

Research centered on the response of A. lacustris to the lowering of water levels is needed. As water levels decrease the dissected lower leaves (which were once submerged) wither and drop, while the plant produces new growth of broad leaves. Is it advantageous for the plant to have greater leaf surface area from dissected underwater leaves? Is this related to oxygen or sunlight deficiencies? Are there different frequencies of light being utilized by the plant while it is submerged in water, compared to when it is more terrestrial with newly-formed broad leaves (Summers 1993)? Is there a change in the system of photosynthesis during this transition?

Additional topics: An illustration of A. lacustris can be found in: Sabourin 1991, Godfrey and Wooten 1981, Steyermark 1963, Gleason 1952.

Range distribution maps for the species can be found in the following sources: Arkansas (Smith 1988); Canada (Sabourin 1991); Indiana (Deam 1940); Missouri (Steyermark 1963); Ohio (McCormac 1992a); United States (Al-Shehbaz and Bates 1987).
Population/Occurrence Delineation Not yet assessed
Population/Occurrence Viability
U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
NatureServe Conservation Status Factors Edition Date: 03Feb1994
NatureServe Conservation Status Factors Author: M. Penskar, D. White, W.R. Ostlie, rev. D. Gries (1998)
Management Information Edition Date: 10Feb1994
Management Information Acknowledgments: We are indebted to all the botanists, ecologists, information managers and others who took the time to provide the information necessary for the preparation of this and many other Element Stewardship Abstracts.
Element Ecology & Life History Edition Date: 11Feb1992

Botanical data developed by NatureServe and its network of natural heritage programs (see Local Programs), The North Carolina Botanical Garden, and other contributors and cooperators (see Sources).

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