Maine Field Guide to Invasive Aquatic Plants and their common native look-alikes Second Edition Lake Stewards of Maine 24 Maple Hill Road Auburn, Maine 04210 207-783-7733 www.mainevlmp.org ©2018 Lake Stewards of Maine Volunteer Lake Monitoring Program ACKNOWLEDGEMENTS INTRODUCTION ................................................. 1 SECTION 1. BACKGROUND INFORMATION Using the Field Guide .............................................. 2 Plant Communities ................................................ 4 Plant Structure ................................................... 7 Plant Identification Key............................................ 13 SECTION 2. MAINE'S ELEVEN MOST UNWANTED INVASIVE AQUATIC PLANTS FLOATING-LEAF PLANTS Water Chestnut (Trapa natans) ...................................... 20 Yellow Floating Heart (Nymphoides peltata) ............................. 22 European Frogbit (Hydrocharis morsus-ranae)............................ 24 SUBMERSED PLANTS WITH FINELY-DIVIDED LEAVES Fanwort (Cabomba caroliniana) ...................................... 26 Water-milfoils (Myriophyllum) Eurasian Water-milfoil (M. spicatum) .............................. 28 Variable Water-milfoil (M. heterophyllum) .......................... 30 TABLE OF CONTENTS TABLE Invasive Water-milfoil Hybrid (M. heterophyllum x M. laxum) ............32 Parrot Feather (M. aquaticum) ................................... 34 SUBMERSED PLANTS WITH UNDIVIDED, BLADE OR STRAP SHAPED LEAVES Brazilian Waterweed (Egeria densa) ................................... 36 Hydrilla (Hydrilla verticillata) ....................................... 38 Spiny Naiad (Najas minor) ......................................... 42 Curly-leaf Pondweed (Potamogeton crispus) ............................. 44 SECTION 3. COMMON NATIVE LOOK-ALIKE PLANTS European Frogbit AND Yellow Floating Heart LOOK-ALIKES Watershield (Brasenia schreberi) ...................................... 50 Fragrant Waterlily (Nymphaea odorata) ................................ 52 Spatterdock (Nuphar variegata) ...................................... 54 Little Floating Heart (Nymphoides cordata) ............................. 56 FANWORT AND INVASIVE MILFOIL LOOK-ALIKES Bladderworts (Utricularia).......................................... 58 Common Bladderwort (U. vulgaris) Floating Bladderwort (U. radiata) Large Purple Bladderwort (U. purpurea) Northern Bladderwort (U. intermedia) Hornworts (Ceratophyllum) ......................................... 62 Coontail (C. demersum) Spiny Hornwort (C. echinatum) Mermaid Weeds (Proserpinaca) ............ 64 Common Mermaid Weed (P. palustris) Comb-leaf Mermaid Weed (P. pectinata) Water Marigold (Bidens beckii) ...................................... 66 Water Crowfoots (Ranunculus) ...................................... 68 White Water Crowfoot (R. aquatilis) Yellow Water Crowfoot (R. flabellaris) Water-milfoils (Myriophyllum) ...................................... 70 Alternate-flowered Water-milfoil (M. alterniflorum) Northern Water-milfoil (M. sibiricum) Whorled Water-milfoil (M. verticillatum) Farwell’s Water-milfoil (M. farwellii) Low Water-milfoil (M. humile) Water-milfoil Species Comparison Chart ....... .78 BRAZILIAN WATERWEED AND HYDRILLA LOOK-ALIKES Waterweeds (Elodea) ............................................. 80 Common Waterweed (E. canadensis) Slender Waterweed (E. nuttallii) Mare’s Tail (Hippuris vulgaris) ...................................... 82 Water Starworts (Callitriche) ........................................ 84 Common Water Starwort (C. palustris) Large Water Starwort (C. heterophylla) TABLE OF CONTENTS TABLE SPINY NAIAD LOOK-ALIKES Naiads (Najas) ................................................... 86 Slender Naiad (N. flexilis) Thread-Like Naiad (N. gracillima) Stoneworts (Nitella and Chara) ...................................... 90 Pondweeds (Potamogeton) .............................................92 Northern Snail-seed Pondweed (P. spirillus) Slender Pondweeds (P. pusillus, P. berchtoldii, P. gemmiparus) CURLY-LEAF PONDWEED LOOK-ALIKES Pondweeds (Potamogeton) .......................................... 96 Clasping-leaf Pondweeds Perfoliate Pondweed (P. perfoliatus) Red-head Pondweed (P. richardsonii) Large-leaf Pondweed (P. amplifolius) Red Pondweed (P. alpinus) Variable Pondweed (P. gramineus) White-stem Pondweed (P. praelongus) SECTION 4. ADDITIONAL INFORMATION Conducting a Screening Survey .................................... 106 If You Find a Suspicious Plant...................................... 112 Other Invaders on Maine’s Radar Screen .............................. 115 Preventing Spread: Clean. Drain. Dry ................................ 131 Sources ....................................................... 132 Glossary....................................................... 140 Index to Plants by Common Name.................................. 144 Index to Plants by Scientific Name .................................. 146 The revision and printing of this publication was funded in large part by: Ram Island Conservation Fund through the Maine Community Foundation with additional support from Boater participation in Maine’s Lake and River Protection Sticker Program Maine Department of Environmental Protection Patagonia Margaret E. Burnham Charitable Trust i Lake Stewards of Maine This book is dedicated to all who contribute time and effort to the hunt for aquatic invaders Maine Volunteer Lake Monitoring Program ii Lake Stewards of Maine (LSM, formerly known as the Maine Volunteer Lake Monitoring Program), formed in 1971, is the longest-standing citizen lake monitoring program in the U.S., and the largest provider of scientific lake data in Maine. Over 1,200 LSM-certified volunteers currently monitor roughly 500 lakes throughout the state. The Mission of Lake Stewards of Maine is to help protect Maine lakes through widespread citizen participation in the gathering and dissemination of credible scientific information pertaining to lake health. Lakes Stewards of Maine trains, certifies and provides technical support to hundreds of volunteers who monitor a wide range of indicators of water quality, assess watershed health and function, and screen lakes for invasive aquatic plants and animals. In addition to being the primary source of lake data in the State of Maine, LSM volunteers benefit their local lakes by playing key stewardship and leadership roles in their communities. The wide range of data collected by our volunteers is the cornerstone of the foundation of knowledge for Maine lakes. Data collected by LSM strengthens watershed education and conservation initiatives, and helps motivate positive action toward the protection and restoration of Maine lakes. Lake Stewards of Maine has been a collaborative enterprise from the outset. Our partners include state agencies, such as the Maine Departments of Environmental Protection and Inland Fisheries and Wildlife, and the Maine Natural Areas Program, public water utilities, including the Maine Water Utilities Association, the Portland Water District and the Auburn Water District, educational institutions, including the University of Maine and Saint Joseph’s College, Maine- based lake conservation organizations including the Maine Lakes Society and Lakes Environmental Association, and others, including individual lake associations and watershed conservation groups, community planners, private citizens, businesses, and others. In 2001, in response to the growing threat to Maine lakes by non-native aquatic organisms, LSM expanded its focus to address this looming menace. Since that time, LSM has worked with our collaborative partners to develop a wide array of programs and resources to support and strengthen Maine's Invasive Aquatic Species Action Plan, playing an active leadership role in all of the three key strategies of the plan: prevention, early detection, and rapid response and management. In particular, LSM has focused upon the issue of early detection. Lake Stewards of Maine’s Invasive Plant Patrol Program (IPP) is widely recognized--nationally and internationally--as one of the most comprehensive and successful training programs of its kind. Nearly all of the aquatic invaders now known to be present in Maine were first detected by alert and informed citizens. Lake Stewards of Maine has played a critical role in raising public awareness about the threat of aquatic invaders in Maine. This Field Guide is one of several resources developed by LSM to help the public recognize and report occurrances of aquatic invaders. We hope you find it helpful. Thank you for your efforts to protect Maine waters! ~ The Authors iii Lake Stewards of Maine ACKNOWLEDGEMENTS The second edition of Maine’s Field Guide to Invasive Aquatic Plants continues to build upon an earlier publication titled Field Guide to Invasive Aquatic Plants, written by Amy Shnur and Scott Williams of the Maine Volunteer Lake Monitoring Program. We thank the numerous volunteers, professionals, educators, students and others who have field-tested earlier versions of this publication, and have provided helpful suggestions for the on-going improvement of this resource. Project Manager Roberta Hill Lead Authors Roberta Hill and Scott Williams Maine Volunteer Lake Monitoring Program ACKNOWLEDGEMENTS Reviewers and Editors of Original Edition Ann Bove, Roy Bouchard, Paul Gregory Christine Guerette, Sarah Gross, Karen Hahnel, C. Barre Hellquist, Richard Jennings, Robert Johnson, John MacKenzie, John McPhedran, Amy Smagula Reviewers and Editors of Current Edition