United States

Aconite

Aconitum napellus

Critically Endangered

Admiralty Island Meadow Vole (Admiraltiae)

Microtus pennsylvanicus

Agrimony

Agrimonia eupatoria

Near Threatened

Ajuga

Ajuga reptans

Endangered

Alder

Alnus glutinosa

Alder leaf beetle

Agelastica alni

Alder Spittlebug

Aphrophora alni

All Species in United States

Nylander'S Tile Lichen

Lecidea nylanderi

Data Deficient

Oak

Quercus palustris

Oak aphid

Myzocallis castanicola

Oak aphid

Tuberculatus annulatus

Oak Curtain Crust

Hymenochaete rubiginosa

Oakes' Pondweed

Potamogeton oakesianus

Oakes scalewort

Frullania oakesiana

Endangered

Oak Leaf Blister

Taphrina caerulescens

Oakleaf phylloxera aphid

Phylloxera glabra

Oak-Loving Gymnopus

Gymnopus dryophilus

Oak Mazegill

Daedalea quercina

Oak Mildew

Erysiphe alphitoides

Oak Milk-Cap

Lactarius quietus

Oak Moss

Evernia prunastri

Oak wilt fungus

Ceratocystis fagacearum

Oblongleaf orache

Atriplex oblongifolia

oblong orb mussel

Musculium transversum

Obscure Drill

Dichrorampha aeratana

obscure mealybug

Pseudococcus viburni

Obscure morning-glory

Ipomoea obscura

Ocean Sunfish

Mola mola

Ocellated Darner

Boyeria grafiana

Ocellated Emerald

Somatochlora minor

Ochre Bracket

Trametes ochracea

Ochre Club

Clavariadelphus ligula

Ochre Gillgobbler

Hypomyces lateritius

Ochre Spreading Tooth

Steccherinum ochraceum

Ocillate rove beetle

Omalium rivulare

Octagonal-tail worm

Dendrobaena octaedra

Odd beetle

Thylodrias contractus

Oeder's apple moss

Plagiopus oederianus

Ogden'S Pondweed

Potamogeton ogdenii

Oil palm

Elaeis guineensis

Okie bean

Dipogon lignosus

Okra

Abelmoschus esculentus

Oldfashioned weigela

Weigela florida

Oldfield grass

Anthephora hermaphrodita

Old Gray Ruffles

Parmotrema tinctorum

Old-Growth Clam Lichen

Xylopsora friesii

Oldham's baby's-breath

Gypsophila oldhamiana

old house borer

Hylotrupes bajulus

Old-man-in-the-spring

Senecio vulgaris

Old Man Of The Woods

Strobilomyces strobilaceus

Endangered

Old Man'S Beard

Tillandsia usneoides

Old Man'S Beard Lichen

Usnea barbata

Extinct

Old-Man’S Beard Lichen

Usnea angulata

Oldman's cap

Polycarpaea corymbosa

Extinct

Old Potato Amanita

Amanita solaniolens

Oleander

Nerium oleander

Oleander Aphid

Aphis nerii

Oleander Hawk Moth

Daphnis nerii

Oleander scale

Aspidiotus nerii

Olive

Olea europaea

Olive-Backed Thrush

Catharus ustulatus

Olive Duster

Coniophora olivacea

Olive Lute

Callistosporium luteo-olivaceum

Oliver's touch-me-not

Impatiens sodenii

Olive Scribble Lichen

Opegrapha vulgata

Olive-Side Flycatcher

Contopus cooperi

Near Threatened

Olive Wax Cap

Hygrophorus olivaceoalbus