ERECT EVENING-PRIMROSE
Calyx joined to ovary and often produced beyond it; petals usually 4; stamens usually 4 or 8; ovary inferior; seeds numerous.
Erect Evening-Primrose (Œnothera heterophylla) grows in sandy soil in Florida and on the edge of post oak woods in South-central Texas. The plants bloom in April and May. It is very much like the rhombic evening-primrose (Œnothera rhombipetala) but has slenderer, shorter stems and is not often branched. The petals are similar, and their rhombic shape easily distinguishes both of these plants from other evening-primroses. The rhombic primrose grows 2-3 feet high and is very abundant throughout the sandy area of North-central Texas to Minnesota and Indiana.
There are many yellow evening-primroses very much alike in flower which are usually called buttercups, a name first applied to the crowfoots. The flowers usually have four showy petals which last only a day, opening in the late afternoons and closing in the heat of the following day. The seed capsules are usually long and narrow and are borne below the petals. The fireweed is a well-known member of this group. The water evening-primrose (Jussiæa diffusa) is abundant in ponds in Central and East Texas.
PINK EVENING-PRIMROSE
Pink Evening-Primrose. Pink Buttercup (Hartmannia tetraptera) blooms best in April, but a few scattered plants may continue to bloom through the summer months. It is a perennial plant which does well in cultivation. White, pink, blush, and other shades were introduced by Childs in 1892 from seeds collected in Texas and were known as the Mexican evening-primrose.
The earlier flowers are usually much larger than those which bloom late in the season. The flowers are cup-shaped, 2-4 inches broad, with 4 broad petals marked with deeper-colored veining and greenish-yellow at the base. The sepals are united into a narrow tube above the seed capsule and below the petals. This tube is about as long as the capsule, sometimes a little shorter. The sepals do not overlap, are slow about splitting, and are pushed to one side of the flower by the opening petals. The seeds are borne in a club-shaped capsule which is prominently ridged, the slender base being as long as the enlarged seed-bearing portion.
The stems are usually trailing and branched at the base, sometimes forming clumps two or more feet broad. The leaves are quite variable in shape but are generally oblong and narrowed at the base, with margins ranging from entire to deeply lobed and divided.
The group name honors Emanuel Hartmann of Louisiana; “tetraptera” is from the Greek meaning “four-winged” and refers to the shape of the seed-capsule. The plants in this group are sometimes placed with the yellow evening-primroses of the Œnothera group, but characteristics other than color separate them.