An earlier draft of this has now been replaced with the content published in the Maine Natural History Observer 2023, Issue 1
We discovered that Lake Arrowhead (York County) has a well-established population of Large Floating Bladderwort (Utricularia inflata), a native to the southeastern parts of the United States, in late 2021 (The Observer 2022, Issue 2). It was curious to us that it hadn’t been previously detected or documented, since it appears to be pervasive, and in places, plentiful. We realized that this plant may have gone undetected because its distinctive floating radial arms only appear during early spring and late fall, when human activities on the water are minimal. Additionally, flowering specimens were only found in protected, shallow coves that are not frequently traversed.
As amateur aquatic plant patrollers, we had been mistaking the non-blooming, floating foliage of U. inflata for the Northeast native Common Bladderwort (Utricularia vulgaris). We present here some field characteristics that allow these plants to be distinguished from each other, without the need for botanical descriptions that refer to flowers. This is especially important because flowers are absent most of the time.
Figure 2. Diagrammatic representation of U. inflata branching pattern
Figure 3. U. inflata branching detail
U. vulgaris, on the other hand, does not produce a hexagonal branching pattern. This is clear in Fig. 4.
Figure 4. Branching pattern of U. vulgaris
Bladder spatial distribution:
The bladders of U. vulgaris appear in distinctive linear clusters (Fig. 5).
Untangling the Bladderworts
By Debbie Broderick & Dale Schultz
(Photos by the authors)
We discovered that Lake Arrowhead (York County) has a well-established population of Large Floating Bladderwort (Utricularia inflata), a native to the southeastern parts of the United States, in late 2021 (The Observer 2022, Issue 2). It was curious to us that it hadn’t been previously detected or documented, since it appears to be pervasive, and in places, plentiful. We realized that this plant may have gone undetected because its distinctive floating radial arms only appear during early spring and late fall, when human activities on the water are minimal. Additionally, flowering specimens were only found in protected, shallow coves that are not frequently traversed.
As amateur aquatic plant patrollers, we had been mistaking the non-blooming, floating foliage of U. inflata for the Northeast native Common Bladderwort (Utricularia vulgaris). We present here some field characteristics that allow these plants to be distinguished from each other, without the need for botanical descriptions that refer to flowers. This is especially important because flowers are absent most of the time.
Little Floating Bladderwort (Utricularia radiata) has a flower structure similar to U. inflata. We arranged all three next to each other in Fig. 1 below to showcase their vegetative features when flower floats and winter buds are absent.
Figure 1. Stems and foliage of U. radiata (left), U. inflata (center) and U. vulgaris (right)
The delicate vegetation of U. radiata clearly distinguishes it from both U. inflata and U. vulgaris and is therefore excluded from this discussion.
In comparing U. inflata and U. vulgaris, we found two characteristics which allow them to be differentiated reliably in the field: Branching pattern of leaflets, and bladder spatial distribution.
Branching pattern of leaflets:
Utricularia inflata leaflets branch at approximately 120° angles. It has the appearance of an incomplete honeycomb-like pattern, reminiscent of fractals of decreasingly sized hexagons, as illustrated in Fig. 2 and 3.
The delicate vegetation of U. radiata clearly distinguishes it from both U. inflata and U. vulgaris and is therefore excluded from this discussion.
In comparing U. inflata and U. vulgaris, we found two characteristics which allow them to be differentiated reliably in the field: Branching pattern of leaflets, and bladder spatial distribution.
Branching pattern of leaflets:
Utricularia inflata leaflets branch at approximately 120° angles. It has the appearance of an incomplete honeycomb-like pattern, reminiscent of fractals of decreasingly sized hexagons, as illustrated in Fig. 2 and 3.
Figure 2. Diagrammatic representation of U. inflata branching pattern
Figure 3. U. inflata branching detail
U. vulgaris, on the other hand, does not produce a hexagonal branching pattern. This is clear in Fig. 4.
Figure 4. Branching pattern of U. vulgaris
Bladder spatial distribution:
The bladders of U. vulgaris appear in distinctive linear clusters (Fig. 5).
Figure 5. U. vulgaris showing linear appearance of bladders, indicated with red annotations
In contrast, the bladders of U. inflata have a more uniform spatial distribution (Fig. 6). In summary, when floats are absent, we find the easiest differentiators to be the hexagonal pattern, and spatial distribution of the bladders. Once one sees these patterns, one can quickly separate them, without needing a hand lens and a technical botanical description.
Figure 6. Spatial distribution of bladders in U. inflata
We consulted the following texts for guidance when examining our samples:
In contrast, the bladders of U. inflata have a more uniform spatial distribution (Fig. 6). In summary, when floats are absent, we find the easiest differentiators to be the hexagonal pattern, and spatial distribution of the bladders. Once one sees these patterns, one can quickly separate them, without needing a hand lens and a technical botanical description.
Figure 6. Spatial distribution of bladders in U. inflata
We consulted the following texts for guidance when examining our samples:
Crowe, G.. & Barre Hellquist, C. 2006. Aquatic and Wetland Plants of Northeastern North America, Volume I : A Revised and Enlarged Edition of Norman C. Fassett's A Manual of Aquatic Plants, 1st edition, University of Wisconsin Press.
Hotchkiss, N. 2011. Common Marsh, Underwater and Floating-leaved Plants of the United States and Canada, Revised edition, Dover Publications.
Lake Stewards of Maine, 2018. Maine Field Guide to Invasive Aquatic Plants and their common native look-alikes, 2nd edition.
Temte, J., Korth, R. & Borman, S. 1997. Through the Looking Glass: A Field Guide to Aquatic Plants, University of Wisconsin Press
Lake Stewards of Maine, 2018. Maine Field Guide to Invasive Aquatic Plants and their common native look-alikes, 2nd edition.
Temte, J., Korth, R. & Borman, S. 1997. Through the Looking Glass: A Field Guide to Aquatic Plants, University of Wisconsin Press