Mock Orange: Philadelphus lewisii
Bedstraw Family, Madder Family: Square stems, often with tiny clingy hairs. Leaves opposite or whorled (The many leaves arise from the same spot on the stem, but on all sides of the stem.) The white flowers are usually very small, with the 4 petals shaped as a cross.
Bleeding Heart Family: Petals Irregular, of different sizes and Shapes
Yellow Bee Plant, Yellow Spiderflower, Yellow Spider Flower: Cleome lutea ssp. lutea (Synonyms: Cleome lutea var. lutea, Peritoma lutea)
Dogwood Family: 4 large white showy bracts which may be mistaken as petals. These white bracts surround a tiny yellow cluster of flowers. Leaves opposite. Dogwoods may be trees or small ground covers.
Evening-primrose Family: There are 4 of each of the petals, sepals, and stamens. The style (long projection from the central ovary has a 4-part cross (X) at its end, or is bulb-like.
Gentian Family: Petals in 4s or 5s.
Mock Orange (Hydrangea) Family:
Mustard Family: Urn-like flowers with 4 petals shaped as an cross or an X when viewed from above. The flowers have 6 stamens (4 above, 2 below).
Plantain Family: This family actually has flowers with 5 petals, but the upper two are joined. Small cream, brown or green flowers on erect leafless stalk. The leaves are basal and appear to have parallel leaf veins.
Poppy Family: Four large, colorful, showy petals. Poppies have many stamens surrounding a swollen central ovary. The sepals fall off the flower as it opens.
Staff-tree Family: Petals in 4s or 5s, depending on the genus.
Teasel Family: Common Teasel, Fuller's Teasel, Gypsy-combs, Teasel, Wild Teasel: Dipsacus fullonum (Synonyms: Dipsacus fullonum ssp. fullonum, Dipsacus fullonum ssp. sylvestris, Dipsacus sylvestris)