- Pale Corydalis
- Pale Indian Plantain
- Parsnip, Smooth Meadow
- Partridgeberry
- Partridgepea, Common
- Peppermint
- Periwinkle
- Phlox, Downy
- Phlox, Garden
- Phlox, Mountain or Wideleaf
- Phlox, Moss
- Phlox, Swordleaf
- Phlox, Wild Blue
- Pilewort
- Pimpernel
- Pimpernel, Mountain or Shalebarren
- Pimpernel, Yellow
- Pineapple Weed
- Pinesap
- Pink Ladies Slipper
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- Pinweed, Narrow-leaved
- Pitcherplant, Purple
- Plantain, American
- Plantain, English
- Plantain, Bracted
- Plantain, Great Indian
- Plantain, Pale Indian
- Pogonia, Large Whorled
- Poison Hemlock
- Poison Ivy
- Pokeweed
- Poppy, Prickly
- Prickly Pear, Eastern
- Proliferours Pink
- Purple Dead Nettle
- Purple-flowering Raspberry
- Purple-leaved Willow Herb
- Putty-root
- Pyrola, Round-leaved
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