Caespitosa: Answers to key questions in Budd's Flora and Flora of Alberta leading to this species. 

	plants lacking leafy stems, leaves forming a rosette; NOT [plants with leafy stems]
	petals more than 20 or 25 mm long; NOT [petals less than 20 or 25 mm long]
	petals white, aging to pink; NOT [petals yellow, aging to pink]
	stigma with 4 linear lobes; NOT [stigma capitate]
	capsule with double crests at angles; NOT [capsule narrowly winged at angles] (BF)
	capsules NOT winged; NOT [capsules distinctly wing-margined] (FOA)

Oenothera: Answers to key questions in Budd's Flora  and Flora of Alberta leading to this genus. 

	hypanthium prolonged beyond the ovary
	flower parts in 4’s; NOT [flower parts in 2’s]
	sepals commonly reflexed; NOT [sepals erect]
	petals yellow, white or pink; NOT [petals purplish]
	anthers attached near their middle, usually versatile; NOT [anthers attached near their base, erect]
	ovary 4-loculed; NOT [ovary2-loculed]
	fruit a capsule; NOT [fruit nut-like]
	fruit opening by valves; NOT [fruit indehiscent]
	fruit opening with 4 valves; NOT [capsules opening with 2 valves]
	fruit NOT covered with hooks; NOT [fruit covered with hooked bristles]
	seeds lacking a coma; NOT [seeds with a tuft of hairs (coma) at one end]
	fruit many-seeded; NOT [fruit 1-seeded]

Onagraceae: Answers to key questions in Budd's Flora  leading to this family. 

	herbs; NOT [shrubs or trees]
	plants terrestrial; NOT [plants aquatic; leaves submerged or floating], NOT [mud plants with small axillary flowers]
	plants NOT with colored milky juice
	plants with more than one normal leaf
	leaves without stipules, or having glands; NOT [leaves with stipules]
	plants without large petal-like bracts; NOT [plants with an involucre of 4 petal-like bracts]
	flowers with two floral rings, and with each petal distinct from the others]
	parts of flowers in twos or fours; NOT [parts of flowers mostly in fives]
	calyx regular; NOT [calyx irregular, some sepals smaller than others]
	stamens 10 or fewer; NOT [stamens usually more than 10]
	styles single; NOT [styles 2 or more]
	ovary inferior; NOT [ovary superior]